Co-reporter:Vadapalli Chandrasekhar, Gurusamy Thangavelu Senthil Andavan, Ramachandran Azhakar and Balasubramanian Murugesa Pandian
Inorganic Chemistry March 17, 2008 Volume 47(Issue 6) pp:1922-1924
Publication Date(Web):February 14, 2008
DOI:10.1021/ic702500n
The cyclophosphazene hydrazide gem-N3P3Ph2[N(Me)NH2]4 was reacted with o-hydroxybenzaldehyde to afford the multisite coordination ligand gem-N3P3Ph2[N(Me)N═CHC6H4-2-OH]4 (LH4). The latter reacted with copper(II) salts to afford a novel tetranuclear copper assembly {N3P3Ph2[N(Me)N═CHC6H4-2-O]4Cu2}2, which contains, remarkably, 15 contiguous inorganic rings.
Co-reporter:Sourav Biswas, Kochan S. Bejoymohandas, Sourav Das, Pankaj Kalita, Mundalapudi L. P. Reddy, Itziar Oyarzabal, Enrique Colacio, and Vadapalli Chandrasekhar
Inorganic Chemistry July 17, 2017 Volume 56(Issue 14) pp:7985-7985
Publication Date(Web):June 29, 2017
DOI:10.1021/acs.inorgchem.7b00689
The sequential reaction of 2-((6-(hydroxymethyl)pyridin-2-yl)-methyleneamino)phenol (LH2), LnCl3·6H2O, and 1,1,1-trifluoroacetylacetone (Htfa) in the presence of Et3N afforded [Ln(LH) (tfa)2] [Ln = Dy3+ (1), Ln = Tb3+ (2), and Ln = Gd3+ (3)], while under the same reaction conditions, but in the absence of the coligand, another series of mononuclear complexes, namely, [Ln(LH)2]·Cl·2MeOH] [Ln = Dy3+ (4) and Tb3+ (5)] are obtained. Single-crystal X-ray diffraction analysis revealed that the former set contains a mono-deprotonated [LH]− and two tfa ligands, while the latter set comprises of two mono-deprotonated [LH]− ligands that are nearly perpendicular to each other at an angle of 86.9°. Among these complexes, 2 exhibited a ligand-sensitized lanthanide-characteristic emission. Analyses of the alternating current susceptibility measurements reveal the presence of single-molecule magnet behavior for 1 and 4, in the presence of direct-current field, with effective energy barriers of 4.6 and 44.4 K, respectively. The enhancement of the effective energy barrier of the latter can be attributed to the presence of a large energy gap between the ground and first excited Kramers doublets, triggered by the change in coordination environments around the lanthanide centers.
Co-reporter:Debabrata Dhara;Thangavel Vijayakanth;Milan Kr. Barman;Khevath Praveen Kumar Naik;Nicolas Chrysochos;Cem B. Yildiz;Ramamoorthy Boomishankar;Carola Schulzke;Anukul Jana
Chemical Communications 2017 vol. 53(Issue 61) pp:8592-8595
Publication Date(Web):2017/07/27
DOI:10.1039/C7CC03912C
A facile, straightforward synthesis of N-heterocyclic carbene (NHC)-stabilized 1-hydrosilaimine starting from a silicon(IV)-precursor is reported. It has been employed for the addition of an O–H bond of water under ambient conditions without any additional catalyst.
Co-reporter:Sourav Biswas, Joydeb Goura, Sourav Das, Craig V. Topping, Jamie Brambleby, Paul A. Goddard, and Vadapalli Chandrasekhar
Inorganic Chemistry 2016 Volume 55(Issue 17) pp:8422-8436
Publication Date(Web):August 8, 2016
DOI:10.1021/acs.inorgchem.6b01019
Octanuclear heterobimetallic complexes, [Ln4Ni4(H3L)4(μ3-OH)4(μ2-OH)4]4Cl·xH2O·yCHCl3 (Dy3+, x = 30.6, y = 2 (1); Tb3+, x = 28, y = 0 (2) ; Gd3+, x = 25.3, y = 0 (3); Ho3+, x = 30.6, y = 3 (4)) (H5L = N1,N3-bis(6-formyl-2-(hydroxymethyl)-4-methylphenol)diethylenetriamine) are reported. These are assembled by the cumulative coordination action of four doubly deprotonated compartmental ligands, [H3L]2–, along with eight exogenous −OH ligands. Within the core of these complexes, four Ln3+’s are distributed to the four corners of a perfect square grid while four Ni2+’s are projected away from the plane of the Ln4 unit. Each of the four Ni2+’s possesses distorted octahedral geometry while all of the Ln3+’s are crystallographically equivalent and are present in an elongated square antiprism geometry. The magnetic properties of compound 3 are dominated by an easy-plane single-ion anisotropy of the Ni2+ ions [DNi = 6.7(7) K] and dipolar interactions between Gd3+ centers. Detailed ac magnetometry reveals the presence of distinct temperature-dependent out-of-phase signals for compounds 1 and 2, indicative of slow magnetic relaxation. Magnetochemical analysis of complex 1 implies the 3d and the 4f metal ions are engaged in ferromagnetic interactions with SMM behavior, while dc magnetometry of compound 2 is suggestive of an antiferromagnetic Ni–Tb spin-exchange with slow magnetic relaxation due to a field-induced level crossing. Compound 4 exhibits an easy-plane single-ion anisotropy for the Ho3+ ions and weak interactions between spin centers.
Co-reporter:Ramakirushnan Suriya Narayanan and Vadapalli Chandrasekhar
Dalton Transactions 2016 vol. 45(Issue 5) pp:2273-2283
Publication Date(Web):27 Nov 2015
DOI:10.1039/C5DT03537F
The coordination behaviour of hexakis(3-pyridyloxy)cyclophosphazene (L) towards divalent metal ions is described. The reaction of L with hydrated metal nitrates afforded [{N3P3(O-C5H4N-3)6}2{Zn(H2O)3(NO3)}2{Zn(H2O)2(NO3)}2]n[NO3]2n·4nH2O·nCH3OH (1), [{N3P3(O-C5H4N-3)6}2{Zn(H2O)3(NO3)}2{Cu(NO3)}2]n[NO3]2n·4nH2O·nCH3CN (2), [{N3P3(O-C5H4N-3)6}2{(NO3)Cd-(μ-(NO3)-Cd(NO3)2(μ-(NO3)Cd(NO3)}]n·2nCH3OH·3nH2O (3), and [{N3P3(O-C5H4N-3)6}2{Cd(H2O)3(NO3)}2][NO3]2·9H2O (4). 1 and 2 are one-dimensional coordination polymers while 3 is a two-dimensional coordination polymer. On the other hand 4 is a molecular metallamacrocycle. A common feature of 1–4 is the presence of a 20-membered dimetallamacrocyclic motif constructed through the involvement of a pair of cyclophosphazene ligands through their geminal pyridyloxy substituents. The P–N bond distances in L and its metal complexes 1–4 are nearly the same indicating the flexible nature of the coordination pyridyloxy arms present on the cyclophosphazene scaffold.
Co-reporter:Joydeb Goura, Jamie Brambleby, Craig V. Topping, Paul A. Goddard, Ramakirushnan Suriya Narayanan, Arun Kumar Bar and Vadapalli Chandrasekhar
Dalton Transactions 2016 vol. 45(Issue 22) pp:9235-9249
Publication Date(Web):27 Apr 2016
DOI:10.1039/C5DT03871E
Through the use of a multi-site compartmental ligand, 2-methoxy-6-[{2-(2-hydroxyethylamino)ethylimino}methyl]phenol (LH3), the family of heterometallic, trinuclear complexes of the formula [CoIII2Ln(L)2(μ-O2CCH3)2(H2O)3]·NO3·xMeOH·yH2O has been expanded beyond Ln = DyIII to include GdIII (1), TbIII (2), HoIII (3) and ErIII (4) for 1, 3 and 4 (x = 1; y = 1) and for 2 (x = 0; y = 2). The metallic core of these complexes consists of a (CoIII–LnIII–CoIII) motif bridged in a bent geometry resulting in six-coordinated distorted CoIII octahedra and nine-coordinated LnIII monocapped square-antiprisms. The magnetic characterization of these compounds reveals the erbium and terbium analogues to display a field induced single-ion magnetic behavior similar to the dysprosium analogue but at lower temperatures. The energy barrier for the reversal of the magnetization of the CoIII2TbIII analogue is Ueff ≥ 15.6(4) K, while for the CoIII2ErIII analogue Ueff ≥ 9.9(8) K. The magnetic properties are discussed in terms of distortions of the 4f electron cloud.
Co-reporter:Subrata Kundu, N. Nagapradeep, Balaram Mohapatra, Sourav Biswas, Sandeep Verma and Vadapalli Chandrasekhar
CrystEngComm 2016 vol. 18(Issue 25) pp:4807-4817
Publication Date(Web):11 May 2016
DOI:10.1039/C6CE00719H
The reaction of L1H {L1H = 3-(N9-guaninyl)propionic acid} with Me3SnCl or (n-Bu3Sn)2O afforded the 1D coordination polymers, [Me3Sn(L1)]n (1) and [n-Bu3Sn(L1)]n (2) respectively. A reaction between L2H {L2H = 3-(N7-guaninyl)propionic acid} with Me3SnCl also afforded a 1D coordination polymer, [Me3Sn(L2)]n (3). A similar reaction between L3H [uracil-6-carboxylic acid] with (Ph3Sn)2O in a 2:1 ratio afforded a dimer [(n-Bu3SnL3)2·H2O] (4). A mononuclear compound [Me3Sn(L4)·H2O] (5) was obtained in a 1:1 reaction of 3-{N9-(2-aminopurinyl)}propanoic acid (L4H) with Me3SnCl. Complexes 1–5 show rich supramolecular structures in the solid state as a result of several intermolecular interactions. Thus, in the one-dimensional coordination polymer 3, triple hydrogen bonding (GG), between inter-chain guanine units has been observed. Similarly a homo orotatequartet has been observed in 4 as a result of intermolecular interactions.
Co-reporter:Joydeb Goura and Vadapalli Chandrasekhar
Chemical Reviews 2015 Volume 115(Issue 14) pp:6854
Publication Date(Web):June 29, 2015
DOI:10.1021/acs.chemrev.5b00107
Co-reporter:Joydeb Goura, Amit Chakraborty, James P. S. Walsh, Floriana Tuna, and Vadapalli Chandrasekhar
Crystal Growth & Design 2015 Volume 15(Issue 7) pp:3157
Publication Date(Web):May 19, 2015
DOI:10.1021/acs.cgd.5b00588
The sequential reaction of the multisite coordination ligand 6,6′-{(2-(dimethylamino)ethyl azanediyl)bis(methylene)}bis(2-methoxy-4-methylphenol) (LH2) with LnIII salts (Ln = Gd, Tb, Dy) and Co(ClO4)2·6H2O in the presence of triethylamine and pivalic acid (pivH) in ambient conditions afforded a series of isostructural heterometallic hexanuclear CoII/LnIII complexes with the general formula [CoII2Ln4(μ3-OH)4(L)2(piv)8(μ-OH2)]·wCH3C·xCH2Cl2·yCH3OH·zH2O (1: Ln = Gd, w = 5, x = 2, y = 0, z = 2; 2: Ln = Tb, w = 7, x = 4, y = 2, z = 0; 3: Ln = Dy; w = 4, x = 2, y = 2, z = 0). Compounds 1 and 3 crystallize in the monoclinic system, space group P21/n (Z = 4), while compound 2 crystallizes in P2/n (Z = 2). The hexanuclear core of the complexes comprises of a nonplanar arrangement of lanthanide ions bridged by two μ3-OH ligands. This tetranuclear motif is connected to the CoII ions by two μ3-OH ligands. The overall structure contains four interlinked incomplete cubic subunits (two CoIILnIII2O4 and two LnIII3O4) that are connected to each other by the sharing of two LnIII ions. The lanthanide centers are eight-coordinate (distorted trigonal-dodecahedron) and nine-coordinate (distorted monocapped square-antiprism), while the cobalt centers are six-coordinate (distorted octahedral). Magnetic measurement of the dysprosium analogue shows a slow magnetic relaxation.
Co-reporter:Amit Chakraborty, Prasenjit Bag, Joydeb Goura, Arun Kumar Bar, Jean-Pascal Sutter, and Vadapalli Chandrasekhar
Crystal Growth & Design 2015 Volume 15(Issue 2) pp:848
Publication Date(Web):January 6, 2015
DOI:10.1021/cg501640y
The reaction of a new compartmental ligand, H3L [H3L = N′-(2-hydroxy-3-methoxybenzylidene)-2-(-2-hydroxy-3-methoxybenzylideneamino)benzohydrazide], with lanthanide salts followed by reaction of MnII salts in presence of triethylamine along with pivalic acid afforded heterometallic hexanuclear complexes, [{LMn(Cl)(μ3-OH)Gd2(μ3-OH)(μ-Piv)2}2·3MeCN·7MeOH·H2O] (1), [{LMn(Cl)(μ3-OH)Tb2(μ3-OH)(μ-Piv)2}2·8MeCN] (2), [{LMn(Cl)(μ3-OH)Dy2(μ3-OH)(μ-Piv)2}2·2Et2O·4MeCN·3H2O] (3), and [{LMn(Cl)(μ3-OH)Ho2(μ3-OH)(μ-Piv)2}2·8MeCN] (4). All of the complexes are isostructural, in which two trianionic ligands [L3–] hold the six metal ions, affording a chair-shaped hexametallic core. The asymmetric unit contains half of the molecule, where Mn(II) ions occupy the inner coordination pocket of the ligand in a distorted square pyramidal geometry (NO3Cl) and the two lanthanide ions occupy the two outer-coordination pockets. Magnetic measurements reveal that antiferromagnetic interactions take place in complexes 1, 3, and 4. On the other hand, complex 2 shows the presence of ferromagnetic interactions.
Co-reporter:Prasenjit Bag, Chandresh Kumar Rastogi, Sourav Biswas, Sri Sivakumar, Valeriu Mereacre and Vadapalli Chandrasekhar
Dalton Transactions 2015 vol. 44(Issue 9) pp:4328-4340
Publication Date(Web):19 Jan 2015
DOI:10.1039/C4DT03429E
Four dinuclear lanthanide complexes [Gd2 (H2L)2 (µ-piv)2 (piv)2]·2CHCl3 (1), [Tb2 (H2L)2 (µ-piv)2 (piv)2]·2CHCl3 (2), [Dy2 (H2L)2 (µ-piv)2 (piv)2]·2CHCl3 (3) and [Eu2 (H2L)2 (µ-piv)2 (piv)2]·2CHCl3 (4) were synthesized by the reaction of appropriate Ln(III) chloride salts and a multidentate ligand, 2,2′-(2-hydroxy-3-methoxy-5-methylbenzylazanediyl)diethanol (H3L) in the presence of pivalic acid. 1–4 are neutral and are held by two monoanionic, [H2L]− ligands. The two lanthanide ions are doubly bridged to each other via two phenolate oxygen atoms. Both the lanthanide ions are nine coordinated and possess a distorted capped square antiprism geometry. Photophysical studies reveal that Tb3+ (2) and Dy3+ (3) complexes display strong ligand-sensitized lanthanide-characteristic emission. The Tb3+ complex (2) shows a very high overall quantum yield of 76.2% with a lifetime of 1.752 ms. Magnetic studies reveal single-molecule magnet behavior for 3 which shows in its ac susceptibility studies a two-step slow relaxation yielding two effective relaxation energy barriers of ΔE = 8.96 K and 35.51 K.
Co-reporter:Joydeb Goura, James P. S. Walsh, Floriana Tuna, Ritesh Halder, Tapas Kumar Maji, and Vadapalli Chandrasekhar
Crystal Growth & Design 2015 Volume 15(Issue 6) pp:2555
Publication Date(Web):April 29, 2015
DOI:10.1021/cg5017005
The reaction of lanthanide(III) salts with an organodiphosphonic acid under hydrothermal conditions resulted in a P–C bond cleavage affording [{Eu4(PO4)(PO4)0.5×4(PO4)0.25×4(H2O)2}·6H2O]n (1), [{Dy4(PO4)(PO4)0.5×4(PO4)0.25×4(H2O)2}·6H2O]n (2), and [{Gd(PO4)0.5(PO4)0.5(H2O)3}·2H2O]n (3). 1 and 2 are porous 3D coordination polymers whose repeating units possess a dimeric motif. While one lanthanide ion in the dimer is eight-coordinate in a distorted square-antiprismatic geometry, the other is nine-coordinate and present in a distorted monocapped square-antiprismatic geometry. In contrast to 1 and 2, 3 possesses a 2D architecture; the asymmetric unit contains a monomeric GdIII center which is nine-coordinate in a distorted monocapped square-antiprismatic geometry.
Co-reporter:Subrata Kundu and Vadapalli Chandrasekhar
Crystal Growth & Design 2015 Volume 15(Issue 11) pp:5437
Publication Date(Web):September 16, 2015
DOI:10.1021/acs.cgd.5b01064
A series of η6-benzene(tricarbonyl)chromium and cymantrene-containing [cymantrene = cyclopentadienylmanganese(I) tricarbonyl] assemblies supported on organostannoxane platforms are reported. The reaction of [Cr(η6-C6H5CO2H)(CO)3] (L1H) with n-Bu2SnCl2 in a 1:1 ratio afforded the tetranuclear derivative [{n-Bu2Sn}2(μ3-O)(μ-OMe)(L1)]2 (1) whereas a similar reaction carried out in a 2:1 stoichiometry afforded the mononuclear derivative [n-Bu2Sn(L1)2] (2). The reaction of (t-Bu2SnO)3 with L1H in toluene in a 1:3 ratio afforded the hydroxide-bridged dimer, [t-Bu2Sn(μ-OH)(L1)]2 (3). A 1:2 reaction between [{η6-C6H4(COOH)2-1,3}Cr(CO)3] (L2H2) and Me3SnCl afforded a two-dimensional coordination polymer [{Me3Sn}2(μ4-L2)]n (4). A similar reaction between [{η6-C6H4(COOH)2-1,4}Cr(CO)3] (L3H2) and Me3SnCl in a 1:2 ratio also afforded a two-dimensional coordination polymer [{Me3Sn}2(μ4-L3)]n (5). The reaction of L3H2 with Me3SnCl in the presence of 4,4′-bipyridine afforded a 1D-coordination polymer [(Me3Sn)2(μ-L3)(μ-4,4′-bipy)]n (6). The reaction of L3H2 with (Ph3Sn)2O (in a 1:1 ratio) gave a dimer [(H2O)SnPh3(μ-L3)SnPh3(MeOH)] (7). The 1:1 reaction of [Mn(η5-C5H4COOH)(CO)3] (L4H) with Me2SnCl2 yielded the tetranuclear derivative [{Me2Sn}2(μ3-O)(L4)2]2 (8). A similar reaction of [Mn{η5-C5H4C(O)CH2CH2COOH}(CO)3] (L5H) with Me2SnCl2 in a 1:1 ratio also afforded a tetrameric derivative [{Me2Sn}2(μ3-O)(μ2-OMe)(L5)]2 (9). All the compounds were characterized by single crystal X-ray diffraction. Complexes 4 and 5 are planar organometallic 2D-coordination polymers.
Co-reporter:Subrata Kundu, Balaram Mohapatra, Chandrajeet Mohapatra, Sandeep Verma, and Vadapalli Chandrasekhar
Crystal Growth & Design 2015 Volume 15(Issue 1) pp:247-256
Publication Date(Web):November 13, 2014
DOI:10.1021/cg501322w
The reaction of L1H [L1H = 3-(N9-hypoxanthyl)propanoic acid] with Me3SnCl or (n-Bu3Sn)2O afforded the 1D coordination polymers [Me3Sn(L1)]n (1) and [n-Bu3Sn(L1)]n (2), respectively. A similar reaction between L2H [3-{N9-(2-aminopurinyl)}propanoic acid] with (Ph3Sn)2O in a 2:1 ratio afforded a dimer [(L2)(Ph3Sn)L2{Ph3Sn(H2O)}]·3CH3OH·3H2O (3). The reactions of 2-(N9-adeninyl)acetic acid (L3H) and 3-(N9-adeninyl)propanoic acid (L4H) with (Ph3Sn)2O in a 2:1 ratio afforded insoluble intractable products, which, upon addition of dilute HCl in methanol, afforded [{Ph2SnCl3(H2O)}(HL3Me)2Cl]·H2O (4) and [(Ph2SnCl4)(HL4Me)2] (5). Complexes 1–5 show an extensive supramolecular organization in the solid state as a result of several intermolecular interactions, prominent among which are the interactions between the nucleobases.
Co-reporter:Sourav Biswas, Sourav Das, Jan van Leusen, Paul Kögerler and Vadapalli Chandrasekhar
Dalton Transactions 2015 vol. 44(Issue 44) pp:19282-19293
Publication Date(Web):07 Oct 2015
DOI:10.1039/C5DT03060A
The reaction of LnCl3·6H2O (Ln = Dy3+, Tb3+ and Ho3+) with the multisite coordinating ligand N′-(2-hydroxy-3-(hydroxymethyl)-5-methylbenzylidene)acetohydrazide (LH3) in the presence of pivalic acid (PivH) leads to the formation of three isostructural homometallic pentanuclear complexes, [Dy5(LH)4(η1-Piv)(η2-Piv)3(μ2–η2η1Piv)2(H2O)]·Cl·9·5H2O·5MeOH (1), [Tb5(LH)4(η1-Piv)(η2-Piv)3(μ2–η2η1Piv)2(H2O)]·Cl·10.5H2O·2MeOH·2CHCl3 (2) and [Ho5(LH)4(η1-Piv)(η2-Piv)3(μ2–η2η1Piv)2(H2O)]·Cl·14.5H2O·2CHCl3 (3). 1–3 are monocationic and are comprised of four doubly deprotonated [LH]2− ligands along with six pivalate ions. These complexes possess a [2.2] spirocyclic topology formed by the fusion of two triangles of LnIII ions at a common vertex. The magneto chemical analysis reveals the presence of antiferromagnetic exchange interactions at low temperature, and the DyIII complex 1 gives an out-of-phase signal with a small curvature in alternating current (ac) magnetic susceptibility measurement. Application of a 3000 G static field during ac measurement intensifies the signals, revealing a second slow relaxation process in the DyIII analogue.
Co-reporter:Joydeb Goura, James P. S. Walsh, Floriana Tuna and Vadapalli Chandrasekhar
Dalton Transactions 2015 vol. 44(Issue 3) pp:1142-1149
Publication Date(Web):05 Nov 2014
DOI:10.1039/C4DT01603C
The reaction of the hydrazone, 2-methoxy-6-(pyridin-2-yl-hydrazonomethyl) phenol (LH) with lanthanide(III) nitrate salts in the presence of excess triethylamine afforded the heptanuclear Ln(III) complexes: [Gd7(L)6(μ3-OH)8(NO3)4(H2O)]·(NO3)3·8CH3CN·H2O (1), [Tb7(L)6(μ3-OH)8(NO3)4]·(NO3)3·9CH3CN·2CH3OH·3H2O (2), [Dy7(L)6(μ3-OH)8(NO3)4(H2O)]·(NO3)3·7CH3CN·3H2O (3), [Ho7(L)6(μ3-OH)8(NO3)4]·(NO3)3·11CH3CN·2CH3OH·2H2O (4) and [Er7(L)6(μ3-OH)8(NO3)4]·(NO3)3·8CH3CN·2CH3OH (5). Single crystal X-ray diffraction studies reveal that these complexes are tri-cationic, possessing three nitrate counter anions. The heptanuclear ensemble is non-planar and consists of six [L]− and eight μ3-OH ligands. These compounds show an interesting structural motif with two incomplete cubes fused to each other through a common Ln(III) ion. Compound 1 exhibits a magnetocaloric effect, with (−ΔSm(T) = 27.7 J kg−1 K−1 at 3 K and under a field change of 0–7 T), while compound 3 shows slow magnetic relaxation at very low temperatures.
Co-reporter:Dr. Joydeb Goura;Jamie Brambleby;Dr. Paul Goddard;Dr. Vadapalli Chrasekhar
Chemistry - A European Journal 2015 Volume 21( Issue 13) pp:4926-4930
Publication Date(Web):
DOI:10.1002/chem.201406021
Abstract
We report a CoIII2DyIII complex, which shows single-ion-magnet behaviour. AC susceptibility data of this compound reveals the presence of slow relaxation of the magnetization in zero-field below 15 K. The relaxation barrier is 88 K.
Co-reporter:Dr. Sourav Das;Dr. Atanu Dey;Dr. Subrata Kundu;Sourav Biswas;Dr. Ramakirushnan Suriya Narayanan;Dr. Silvia Titos-Padilla;Dr. Giulia Lorusso;Dr. Marco Evangelisti; Enrique Colacio; Vadapalli Chrasekhar
Chemistry - A European Journal 2015 Volume 21( Issue 47) pp:16955-16967
Publication Date(Web):
DOI:10.1002/chem.201501992
Abstract
The reaction of a Schiff base ligand (LH3) with lanthanide salts, pivalic acid and triethylamine in 1:1:1:3 and 4:5:8:20 stoichiometric ratios results in the formation of decanuclear Ln10 (Ln=Dy(1), Tb(2), and Gd (3)) and pentanuclear Ln5 complexes (Ln=Gd (4), Tb (5), and Dy (6)), respectively. The formation of Ln10 and Ln5 complexes are fully governed by the stoichiometry of the reagents used. Detailed magnetic studies on these complexes (1–6) have been carried out. Complex 1 shows a SMM behavior with an effective energy barrier for the reversal of the magnetization (Ueff)=16.12(8) K and relaxation time (τo)=3.3×10−5 s under 4000 Oe direct current (dc) field. Complex 6 shows the frequency dependent maxima in the out-of-phase signal under zero dc field, without achieving maxima above 2 K. Complexes 3 and 4 show a large magnetocaloric effect with the following characteristic values: −ΔSm=26.6 J kg−1 K−1 at T=2.2 K for 3 and −ΔSm=27.1 J kg−1 K−1 at T=2.4 K for 4, both for an applied field change of 7 T.
Co-reporter:Joydeb Goura, Rogez Guillaume, Eric Rivière, and Vadapalli Chandrasekhar
Inorganic Chemistry 2014 Volume 53(Issue 15) pp:7815-7823
Publication Date(Web):July 22, 2014
DOI:10.1021/ic403090z
The reaction of hetero donor chelating mannich base ligand 6,6′-{(2-(dimethylamino)ethylazanediyl)bis(methylene)}bis(2-methoxy-4-methylphenol) with Ni(ClO4)2·6H2O and lanthanide(III) salts [Dy(III) (1); Tb(III) (2); Gd (III) (3); Ho(III) (4); and Er(III) (5)] in the presence of triethylamine and pivalic acid afforded a series of heterometallic hexanuclear Ni(II)–Ln(III) coordination compounds, [Ni3Ln3(μ3-O)(μ3-OH)3(L)3(μ-OOCCMe3)3]·(ClO4)·wCH3CN·xCH2Cl2·yCH3OH·zH2O [for 1, w = 8, x = 3, y = 0, z = 5.5; for 2, w = 0, x = 5, y = 0, z = 6.5; for 3, w = 15, x = 18, y = 3, z = 7.5; for 4, w = 15, x = 20, y = 6, z = 9.5; and for 5, w = 0, x = 3, y = 2, z = 3]. The molecular structure of these complexes reveals the presence of a monocationic hexanuclear derivative containing one perchlorate counteranion. The asymmetric unit of each of the hexanuclear derivatives comprises the dinuclear motif [NiLn(L)(μ3-O)(μ3-OH)(μ-Piv)]. The cation contains three interlinked O-capped clusters: one LnIII3O and three NiIILnIII2O. Each of the lanthanide centers is eight- coordinated (distorted trigonal-dodecahedron), while the nickel centers are hexacoordinate (distorted octahedral). The study of the magnetic properties of all compounds are reported and suggests single molecule magnet behavior for the Dy(III) derivative (1).
Co-reporter:Joydeb Goura, Prasenjit Bag, Valeriu Mereacre, Annie K. Powell, and Vadapalli Chandrasekhar
Inorganic Chemistry 2014 Volume 53(Issue 15) pp:8147-8154
Publication Date(Web):July 21, 2014
DOI:10.1021/ic5012154
The reaction of Fe(ClO4)2·6H2O with t-BuPO3H2 or Cl3CPO3H2 in the presence of an ancillary pyrazole phenolate as a coligand, H2phpzH [H2phpzH = 3(5)-(2-hydroxyphenyl)pyrazole], afforded tetra- and pentanuclear Fe(III) phosphonate complexes [Fe4(t-BuPO3)4(HphpzH)4]·5CH3CN·5CH2Cl2 (1) and [HNEt3]2[Fe5(μ3-O)(μ-OH)2 (Cl3CPO3)3(HphpzH)5(μ-phpzH]·3CH3CN·2H2O (2). Single-crystal X-ray structural analysis reveals that 1 possesses a cubic double-4-ring (D4R) core similar to what is found in zeolites. The molecular structure of 2 reveals it to be pentanuclear. It crystallizes in the chiral P1 space group. Magnetic studies on 1 and 2 have also been carried out, which reveal that the bridging phosphonate ligands mediate weak antiferromagnetic interactions between the Fe(III) ions. Magnetization dynamics of 1 and 2 have been corroborated by a Mössbauer spectroscopy analysis.
Co-reporter:Prasenjit Bag, Amit Chakraborty, Guillaume Rogez, and Vadapalli Chandrasekhar
Inorganic Chemistry 2014 Volume 53(Issue 13) pp:6524-6533
Publication Date(Web):June 6, 2014
DOI:10.1021/ic4028833
The reaction of Ln(III) nitrate and Mn(ClO4)2·6H2O salts in the presence of a multidentate sterically unencumbered ligand, (E)-2,2′-(2-hydroxy-3-((2-hydroxyphenylimino)methyl)-5-methylbenzylazanediyl)diethanol (LH4) leads to the isolation of four isostructural pentanuclear hetereometallic complexes [MnIII2Gd3(LH)4(NO3)(HOCH3)]ClO4·NO3 (1), [MnIII2Dy3(LH)4(NO3)(HOCH3)]ClO4·NO3 (2), [MnIII2Tb3(LH)4(NO3)(HOCH3)]ClO4·NO3 (3), and [MnIII2Ho3(LH)4(NO3)(HOCH3)]ClO4·NO3 (4) with an open-book type structural topology. 1–4 are dicationic and crystallize in the achiral space group, P21/n. A total of four triply deprotonated ligands, [LH]3–, are involved in holding the pentameric metal framework, {MnIII2Ln3}. In these complexes both the lanthanide and the manganese(III) ions are doubly bridged, involving phenolate or ethoxide oxygen atoms. The magnetochemical analysis reveals the presence of global antiferromagnetic interactions among the spin centers at low temperatures in all the four compounds. AC susceptibility measurements show the presence of temperature dependent out-of-phase ac signal for compounds 2 and 4 indicating an SMM behavior.
Co-reporter:Sourav Das, Atanu Dey, Sourav Biswas, Enrique Colacio, and Vadapalli Chandrasekhar
Inorganic Chemistry 2014 Volume 53(Issue 7) pp:3417-3426
Publication Date(Web):March 27, 2014
DOI:10.1021/ic402827b
The reaction of the lanthanide(III) chloride salts [Gd(III), Tb(III), and Dy(III)] with a new chelating, flexible, and sterically unencumbered multisite coordinating compartmental Schiff-base ligand (E)-2-((6-(hydroxymethyl)pyridin-2-yl)methyleneamino)phenol (LH2) and pivalic acid (PivH) in the presence of triethylamine (Et3N) affords a series of tetranuclear Ln(III) coordination compounds, [Ln4(L)4(μ2-η1η1Piv)4]·xH2O·yCH3OH (1, Ln = Gd(III), x = 3, y = 6; 2, Ln = Tb(III), x = 6, y = 2; 3, Ln = Dy(III), x = 4, y = 6). X-ray diffraction studies reveal that the molecular structure contains a distorted cubane-like [Ln4(μ3-OR)4]+8 core, which is formed by the concerted coordination action of four dianionic L2– Schiff-base ligands. Each lanthanide ion is eight-coordinated (2N, 6O) to form a distorted-triangular dodecahedral geometry. Alternating current susceptibility measurements of complex 3 reveal frequency- and temperature-dependent two-step out-of-phase signals under zero direct current (dc) field, which is characteristic of single-molecule magnet behavior. Analysis of the dynamic magnetic data under an applied dc field of 1000 Oe to fully or partly suppress the quantum tunneling of magnetization relaxation process affords the anisotropic barriers and pre-exponential factors: Δ/kB = 73(2) K, τ0 = 4.4 × 10–8 s; Δ/kB = 47.2(9) K, τ0 = 5.0 × 10–7 s for the slow and fast relaxations, respectively.
Co-reporter:Joydeb Goura, James P. S. Walsh, Floriana Tuna, and Vadapalli Chandrasekhar
Inorganic Chemistry 2014 Volume 53(Issue 7) pp:3385-3391
Publication Date(Web):March 10, 2014
DOI:10.1021/ic4027915
The reaction of 2-methoxy-6-(pyridin-2-ylhydrazonomethyl)phenol (LH) with Ln(III) (Ln = Gd, Tb, Dy, Ho) salts in the presence of an excess of triethylamine afforded [Gd4(L)4(μ4-OH)(μ3-OH)2(NO3)4]·(NO3)·4CH3CN·CH3OH·2H2O (1), [Tb4(L)4(μ4-OH)(μ3-OH)2(NO3)4]·(NO3)·4CH3CN·3H2O (2), [Dy4(L)4(μ4-OH)(μ3-OH)2(NO3)4]·(NO3)·6CH3CN·H2O (3), and [Ho4(L)4(μ4-OH)(μ-OH)2(NO3)4]·(NO3)·8CH3CN·3CH3OH·2H2O (4). All four complexes contain a monocationic tetranuclear core with a unique seesaw topology. The tetranuclear assembly is formed through the coordination of four [L]−, one μ4-OH, two μ3-OH, and four chelating nitrate ligands, with a charge-balancing nitrate counteranion. Magnetic studies reveal a weak antiferromagnetic coupling throughout the series. Compound 1 can be modeled well with an isotropic exchange between all centers parametrized by J = −0.09 cm–1. Compound 3 exhibits slow magnetic relaxation at low temperatures.
Co-reporter:Sourav Das, Sakiat Hossain, Atanu Dey, Sourav Biswas, Jean-Pascal Sutter, and Vadapalli Chandrasekhar
Inorganic Chemistry 2014 Volume 53(Issue 10) pp:5020-5028
Publication Date(Web):April 25, 2014
DOI:10.1021/ic500052v
The reaction of lanthanide(III) chloride salts (Gd(III), Dy(III), Tb(III), and Ho(III)) with the hetero donor chelating ligand N′-(2-hydroxy-3-methoxybenzylidene)-6-(hydroxymethyl)picolinohydrazide (LH3) in the presence of triethylamine afforded the hexanuclear Ln(III) complexes [{Ln6(L)2(LH)2}(μ3-OH)4][MeOH]p[H2O]q[Cl]4·xH2O·yCH3OH (1, Ln = Gd(III), p = 4, q = 4, x = 8, y = 2; 2, Ln = Dy(III), p = 2, q = 6, x = 8, y = 4; 3, Ln = Tb(III), p = 2, q = 6, x = 10, y = 4; 4, Ln = Ho(III), p = 2, q = 6, x = 10, y = 2). X-ray diffraction studies revealed that these compounds possess a hexanuclear [Ln6(OH)4]14+ core consisting of four fused [Ln3(OH)]8+ subunits. Both static (dc) and dynamic (ac) magnetic properties of 1–4 have been studied. Single-molecule magnetic behavior has been observed in compound 2 with an effective energy barrier and relaxation time pre-exponential parameters of Δ/kB = 46.2 K and τ0 = 2.85 × 10–7 s, respectively.
Co-reporter:Chandrajeet Mohapatra, Sarita Tripathi, Ganapathi Anantharaman, and Vadapalli Chandrasekhar
Crystal Growth & Design 2014 Volume 14(Issue 7) pp:3182-3185
Publication Date(Web):June 6, 2014
DOI:10.1021/cg500633n
A hexanuclear hexagonal organotin macrocycle [(n-Bu3Sn)6(μ-L)6(I–)2(MeOH)6] (1) was synthesized in a 1:1 reaction of (n-Bu3Sn)2O and 4,5-dicarboxy-1,3-dimethyl-1H-imidazol-3-ium iodide (LH2I). The molecular structure of 1 reveals that it is a 42-membered hexatin macrocycle possessing a C3 (pseudo-S6) symmetry. The alternate up–down arrangement of imidazolium units allows the molecule to assume a chair topology. The hexagonal packing of these macrocycles, in the solid-state, results in nanoscale one-dimensional channels which entrap two I– ions in close proximity (∼3.7 Å) as a result of various supramolecular interactions.
Co-reporter:Amit Chakraborty, Prasenjit Bag, Eric Rivière, Talal Mallah and Vadapalli Chandrasekhar
Dalton Transactions 2014 vol. 43(Issue 23) pp:8921-8932
Publication Date(Web):15 Apr 2014
DOI:10.1039/C4DT00209A
A family of dinuclear 3d–4f heterobimetallic complexes [LNi(H2O)(μ-OAc)Ln(NO3)2]·CH3CN; {Ln = DyIII (1), TbIII (2), HoIII (3), GdIII (4), ErIII (5), YIII (6)} have been synthesized by utilizing a ferrocene-based, dual compartmental ligand H2L. 1–6 are isostructural and crystallize in the triclinic (P) space group. In these complexes NiII is present in the inner coordination sphere of the dianionic [L]2− ligand; LnIII is encapsulated in the outer coordination pocket. NiII shows a 2N, 4O coordination environment in a distorted octahedral geometry, while the LnIII ion possesses a 9O coordination environment in a distorted tricapped trigonal prismatic geometry. ESI-MS studies suggest that the structural integrity of 1–6 is retained in solution. Electrochemical studies reveal that these complexes show a reversible one-electron response typical of the ferrocene motif along with an irreversible one-electron oxidation involving the NiII/NiIII couple. Magnetic studies revealed the presence of ferromagnetic exchange coupling between NiII and LnIII centers as shown by the increase of χMT value upon cooling below 50 K for compounds 1, 2, 4 and 5. Further, dynamic magnetic susceptibility measurements (1–3) confirm the absence of an out-of-phase (χ′′) signal at zero dc fields. However, when these measurements were carried out at 1000 Oe dc field the χ′′ signal was observed, although maxima could not be detected up to 2 K.
Co-reporter:Sakiat Hossain, Sourav Das, Amit Chakraborty, Francesc Lloret, Joan Cano, Emilio Pardo and Vadapalli Chandrasekhar
Dalton Transactions 2014 vol. 43(Issue 26) pp:10164-10174
Publication Date(Web):11 Apr 2014
DOI:10.1039/C4DT00465E
The reaction of 8-quinolinol-2-carboaldoxime (LH2) with NiII and LnIII salts afforded the heterometallic decanuclear compounds [Ni8Dy2(μ3-OH)2(L)8(LH)2(H2O)6](ClO4)2·16H2O (1), [Ni8Gd2(μ3-OH)2(L)8(LH)2(H2O)4(MeOH)2](NO3)2·12H2O (2), [Ni8Ho2(μ3-OH)2(L)8(LH)2(H2O)4(MeOH)2](ClO4)2·2MeOH·12H2O (3) and [Ni8Tb2 (μ3-OH)2(L)8(LH)2(MeOH)4(OMe)2]·2CH2Cl2·8H2O (4). While compounds 1–3 are dicationic, compound 4 is neutral. These compounds possess an S-shaped architecture and comprise a long chain of metal ions bound to each other. In all the complexes, the eight NiII and two LnIII ions of the multimetallic ensemble are hold together by two μ3-OH, eight dianionic (L2−) and two monoanionic oxime ligands (LH−) whereas compound 4 has two μ3-OH, eight dianionic (L2−), two monoanionic oxime ligands (LH−) and two terminal methoxy (MeO−) ligands. The central portion of the S-shaped molecular wire is made up of an octanuclear NiII ensemble which has at its two ends the LnIII caps. Magnetic studies on 1–4 reveal that the magnetic interactions between neighboring metal ions are negligible at room temperature. On the other hand, at lower temperatures in all the compounds anti-ferromagnetic interactions seem to be dominated. Analysis of the magnetic data for the GdIII derivative indicates NiII–NiII anti-ferromagnetic interactions and GdIII–NiII ferromagnetic interactions at low temperatures. A theoretical density functional study on the magnetic behavior of the GdIII derivative suggests that while the weak ferromagnetic interaction between GdIII and NiII is in line with the expectation of the magnetic interactions between orthogonal d and f orbitals, antiferromagnetic NiII–NiII interactions are related to the wide Ni–O–Ni angles (∼102°) and quasi-planar conformation of the Ni2O2 core.
Co-reporter:Vadapalli Chandrasekhar, Atanu Dey, Sourav Das and Subrata Kundu
CrystEngComm 2014 vol. 16(Issue 7) pp:1304-1310
Publication Date(Web):30 Oct 2013
DOI:10.1039/C3CE41863D
The reaction of a multisite coordination ligand (LH3) with LnCl3·6H2O, followed by the addition of Mn(OAc)2·4H2O, sodium azide and pivalic acid in the presence of triethylamine in a 2:1:1:4:4:6 (LH3:LnCl3:Mn(OAc)2:NaN3:pivalic acid:Et3N) stoichiometric ratio afforded a series of heterometallic pentanuclear neutral complexes containing a [MnIII3LnNa] core {Ln = Dy (1), Tb (2), Gd (3) and Nd (4)}. The oxidation states of the MnIII ions were confirmed by BVS calculation. All the complexes were characterized by X-ray crystallography. The pentametallic aggregates form a trigonal-bipyramidal geometry in which the three MnIII ions are in the equatorial plane whereas the sodium and lanthanide ions are in the apical positions. Three different types of MnIII ions are present in the complexes and all are in a distorted octahedral geometry. An all-oxygen environment is found to be present around the lanthanides as well as the sodium ions. The lanthanide ion is eight-coordinated and in distorted dodecahedral geometry, while the sodium ion is six-coordinate in a distorted trigonal prismatic geometry in 1–4. The pentanuclear core [MnIII3LnNa] is a subset of one-half of the nonanuclear ensemble, [MnIII6LnNa2]+, reported in literature. We propose that the reduction in the nuclearity of the heterometallic metal ensemble occurs as a result of the influence of hydrogen bonding interactions present in the system.
Co-reporter:Subrata Kundu, Amit Chakraborty, Kunal Mondal, and Vadapalli Chandrasekhar
Crystal Growth & Design 2014 Volume 14(Issue 2) pp:861-870
Publication Date(Web):January 3, 2014
DOI:10.1021/cg4017323
The reaction of ruthenocene carboxylic acid (RcCOOH) with [n-BuSn(O)OH]n, (Ph3Sn)2O, and (PhCH2)3SnCl afforded hexameric compounds [RSn(O)OOCRc]6, R = n-Bu (1), Ph (2), and PhCH2 (3), respectively. These possess a prismane type Sn6O6 core which supports a hexa-ruthenocene periphery. Compounds [{n-Bu2Sn}2(μ3-O)OOCRc2]2 (4) and [n-Bu2Sn(OOCRc)2](5) were formed in the reaction of RcCOOH with n-Bu2SnO in 1:1 and 2:1 reactions, respectively. Compound [t-Bu2Sn(μ–OH)OOCRc]2 (6) is a dimer containing two ruthenocene units, and it was formed in the reaction of RcCOOH with (t-Bu2SnO)3 in a 3:1 ratio. Compounds 1–6 show an extensive supramolecular organization in the solid state as a result of several intermolecular interactions. Compound 1 could be converted quantitatively to a pure phase of the binary oxide, (RuSn)O2 at 400 °C.
Co-reporter:Chandrajeet Mohapatra and Vadapalli Chandrasekhar
Crystal Growth & Design 2014 Volume 14(Issue 2) pp:406-409
Publication Date(Web):January 10, 2014
DOI:10.1021/cg401698a
A metalloligand type of synthetic route has been followed to generate a novel heterometallic three-dimensional (3D)-coordination polymer containing Cu(II) and trimethyltin as nodes. The first step of this synthetic path consisted of the preparation of a two-dimensional-coordination polymer of Cu(II), [Cu(μ-LH)2]n (1) (LH2 = pyridine-2,5-dicarboxylic acid). The reaction of in situ generated 1 with Me3SnCl afforded the heterometallic 3D-coordination polymer, [Cu(Me3Sn)2(μ-L)2]n (2). The latter is a 4,4-connected polymer with a sqc topology. This 3D-framework contains a paddle-wheel-shaped core comprised of two heterometallic (CuII/SnIV) macrocycles.
Co-reporter:Dipankar Sahoo, Ramakirushnan Suriyanarayanan and Vadapalli Chandrasekhar
Dalton Transactions 2014 vol. 43(Issue 28) pp:10898-10909
Publication Date(Web):16 May 2014
DOI:10.1039/C4DT00720D
The reaction of vanadium(III) trichloride with tert-butylphosphonic acid (t-BuPO3H2) in the presence of 1,10-phenanthroline/2,2′-bipyridine as an ancillary ligand in acetonitrile at room temperature afforded two dinuclear dicationic vanadium(IV) complexes [(VO)2(phen)2{t-BuPO2(OH)}2(OH2)2]·2Cl [1] and [(VO)2(bipy)2{t-BuPO2(OH)}2(OH2)2]·2Cl [2]. On the other hand, when the reaction was carried out in methanol, the dinuclear vanadium(V) complex [(VO)2(bipy)2(μ2-O)2(t-BuPO3)2]·2CH3OH·0.5CH2Cl2 [3] was isolated. While 1 and 2 contain two six-membered V2P2O4 rings, 3 contains a unique four-membered V2O2 ring. Replacement of tert-butylphosphonic acid by tritylphosphonic acid (Ph3CPO3H2) under the same reaction conditions in methanol leads to the formation of dicationic trinuclear vanadium(IV) complexes [(VO)3(phen)3(Ph3CPO3)2(OH2)3]·CHCl3·2(OH)·2MeOH·1.5H2O [4] and [(VO)3(bipy)3(Ph3CPO3)2(CH3OH)3]·2(OH)·4CH3OH·5H2O [5]. In these complexes, the triangular V(IV) platform is held together by two bicapping tripodal phosphonate ligands. Replacement of the chelating 2,2′-bipyridine ligand with 3,5-dimethyl-1H-pyrazole, under the same reaction conditions, afforded a tetranuclear vanadium(V) complex [{(VO)4(Ph3CPO3Me)4(μ-O)4}Cl]{3,5-Me2PzH2}·3C7H8·H2O·CH3OH [6]. Remarkably 6 possesses a unique bowl-shaped structure encapsulating a chloride anion.
Co-reporter:Dipankar Sahoo, Ramakirushnan Suriyanarayanan, Ramesh K. Metre and Vadapalli Chandrasekhar
Dalton Transactions 2014 vol. 43(Issue 19) pp:7304-7313
Publication Date(Web):04 Mar 2014
DOI:10.1039/C3DT53614A
The reaction of zinc(II) perchlorate with trichloromethyl phosphonic acid at room temperature afforded, upon crystallization, a two-dimensional layered coordination polymer possessing a dinuclear repeat unit, [{Zn2(Cl3CPO3)2(H2O)3}·1.5H2O]n (1). Modification of the above reaction by involving a co-ligand afforded the tetranuclear complex, [{Zn4(η1-DMPzH)6(Cl3C–PO3)2}(μ-OH)2(ClO4)2] (2). The molecular structure of 2 reveals that the tetranuclear core is non-planar and consists of three contiguous inorganic rings which include one 8-membered Zn2P2O4 ring and two six-membered Zn2PO3 rings. Replacement of Zn(ClO4)2·6H2O with ZnCl2 under the same reaction conditions that afforded 2 allowed the formation of the dinuclear complex [{(ZnCl)2(η2-Pz)2(Cl3CPO3)}(Et3NH)2] (3). 3 possesses a bicyclic core containing a seven-membered Zn2N2O2P ring. In 3, the phosphoryl oxygen atom (PO) is involved in a bifurcated hydrogen bonding interaction with the triethylammonium cation. The reaction of ZnCl2 and 2,3,5,6-(Me)4C6HCH2PO3H2 afforded the octanuclear complex [Zn8(Cl)6{2,3,5,6-(Me)4C6HCH2PO3}6(Et3N)2](Et3NH)2]·2n-hexane·3H2O (4). The core of 4 is ellipsoid-shaped with the end–end polar distance (C–C) being ∼20 Å.
Co-reporter:Ramesh K. Metre, Chandrajeet Mohapatra, Dipankar Sahoo and Vadapalli Chandrasekhar
Dalton Transactions 2014 vol. 43(Issue 8) pp:3364-3371
Publication Date(Web):04 Dec 2013
DOI:10.1039/C3DT53050G
The reactions of RSnCl3 [R = 2-(phenylazo)phenyl] with phosphonic acids, RPO3H2 (R = t-Bu, C6H11) or (ArO)2PO2H (Ar = 4-NO2-C6H5O) in refluxing THF afforded hexatin cages, [(RSn)6(μ-OH)6(μ3-O)2(t-BuPO3)4]·5THF (1), [(RSn)6(μ-OH)6(μ3-O)2(C6H11PO3)4]·THF (2) and [(RSn)6(μ-OH)4(μ3-O)2{(NO2C6H4O)PO3}4]·THF (3), respectively. On the other hand, the reactions of RSnCl3 with 1,1,2,3,3-pentamethylene phosphinic acid [cycPO2H] or Ph2P(O)OH under similar reaction conditions afforded trinuclear O-capped clusters [(RSn)3(μ3-O) (μ2-OH)3 (μ-cycPO2)3] [cycPO2]·CH3CN·H2O (4) and [(RSn)3(μ3-O) (μ2-OH)3 (μ-Ph2PO2)3] [Ph2PO2]·CH3CN·CH2Cl2 (5) respectively. Molecular structures of 1–3 reveal that the intramolecular N→Sn coordination found in RSnCl3 is hemilabile; 1–3 do not contain such a feature and the tin atoms in these compounds are six coordinate, possessing a 1C, 5O coordination environment in a distorted octahedral geometry. The cage structures in 1–3, containing two trinuclear sub-units, are formed as a result of the coordination action of several ligands: 4 μ3-(η1η1η1)[RPO3]2−, 2 μ3-O2− and 6 μ-OH. The molecular structures of 4–5 reveal them to be cationic trinuclear complexes where 3 tin and 4 oxygen atoms occupy the vertices of a distorted cube while one of the vertices is unoccupied. The molecular structures of 4–5 also reveal that the intramolecular N→Sn coordination present in RSnCl3 is absent in these compounds attesting to the hemilabile nature of this interaction.
Co-reporter:Dipankar Sahoo, Ramakirushnan Suriyanarayanan, and Vadapalli Chandrasekhar
Crystal Growth & Design 2014 Volume 14(Issue 6) pp:2725-2728
Publication Date(Web):April 28, 2014
DOI:10.1021/cg5003594
The reaction of Co(ClO4)2·6H2O with (trichloromethyl)phosphonic acid and 3,5-dimethyl-1H-pyrazole in a 3:1:6 ratio in the presence of triethylamine afforded [Co9(3,5-DMPz)12(3,5-DMPzH)6(Cl3CPO3)3](toluene)7 (1). The latter contains three trinuclear (Co3) subunits which are linked to each other by three bridging phosphonate ligands affording a 30-membered macrocycle. 1 contains an equilateral triangle comprising the phosphorus atoms of the bridging phosphonate groups. In solution, 1 breaks down into the trinuclear subunits as detected by electrospray ionization mass spectrometry.
Co-reporter:Prasenjit Bag, Amit Chakraborty, Mathieu Rouzières, Rodolphe Clérac, Raymond J. Butcher, and Vadapalli Chandrasekhar
Crystal Growth & Design 2014 Volume 14(Issue 9) pp:4583-4592
Publication Date(Web):July 21, 2014
DOI:10.1021/cg500677t
Stepwise reaction of LH3 (LH3 = N[CH2CH2N═CH-C6H3-2-OH-3-OMe]3) with Ln(NO3)3·nH2O and potassium oxalate [K2Ox] afforded discrete heterometallic neutral octanuclear complexes [Ln4K4(L)4(μ-H2O)4(NO3)2(μ-Ox)] (Ln = Dy(III), Gd(III), Tb(III), Ho(III); LH3 = N[CH2CH2N═CH-C6H3-2-OH-3-OMe]3; Ox = (C2O4)2–). The molecular structures of 1–4 were confirmed by single-crystal X-ray crystallography. The asymmetric unit of these compounds contains two lanthanide(III) ions and two potassium cations present in the opposite corners of a distorted rectangle. Such a motif is further bridged by an oxalate anion to generate the octanuclear heterometallic complex. The lanthanides are eight-coordinate in a distorted trigonal dodecahedron geometry. On the other hand, the potassium ions adopt a nine-coordinate coordination sphere in a distorted tricapped trigonal prism geometry. Magnetic studies on 1–4 reveal the absence of significant magnetic interactions between the magnetic centers present in these complexes.
Co-reporter:Subrata Kundu, Jitendra Kumar, Arun Kumar, Sandeep Verma, and Vadapalli Chandrasekhar
Crystal Growth & Design 2014 Volume 14(Issue 10) pp:5171-5181
Publication Date(Web):August 19, 2014
DOI:10.1021/cg500900n
The reaction of 3-(N1-uracyl)propanoic acid (LH) with (t-Bu2SnO)3 in a 3:1 ratio afforded the hydroxide-bridged dimer [t-Bu2Sn(μ-OH)L]2 (1). A similar reaction involving bis(tri-n-butyltin)oxide, (n-Bu3Sn)2O, in a 2:1 ratio afforded the one-dimensional (1D) coordination polymer [(n-Bu3SnL)]n (2). Similarly, the reaction of LH with (MeOAr)2TeO in a 2:1 ratio afforded the mononuclear [(MeOAr)2TeL2]·H2O (3). On the other hand, a similar reaction in a 1:1 ratio gave the dinuclear product [{(MeOAr)2TeL}2O]·C2H5OH·CH3OH·H2O (4). The reaction of complex 1 with CuCl2 in a 1:1 ratio yielded [Cu(II)L2H2O]2·6H2O (5). All the complexes show an extensive supramolecular organization in the solid state as a result of several intermolecular interactions. The role of uracil substituents in determining the final course of the supramolecular assembly is discussed. A tetrameric uracil supramolecular motif is formed in the crystal structure of complex 1 as a result of C–H···O interactions. Uracil–water interactions involving only C–H···O interactions have been observed in complex 5.
Co-reporter:Sourav Das;Sakiat Hossain;Atanu Dey;Sourav Biswas;Emilio Pardo;Francesc Lloret;Vadapalli Chrasekhar
European Journal of Inorganic Chemistry 2014 Volume 2014( Issue 21) pp:3393-3400
Publication Date(Web):
DOI:10.1002/ejic.201402195
Abstract
The reaction of 6-formyl-2-(hydroxymethyl)-4-methylphenol (LH2) with NiII and LnIII salts afforded a series of heterometallic pentanuclear compounds [Ni4Ln(L)4(OAc)2(MeOH)4](NO3)(MeOH) [LnIII = Gd (1), Dy (2), Tb (3), Ho (4)]. Four dianionic L2– ligands and two acetate anions hold together four NiII and one LnIII ion to form a Ni4Ln core possessing a distorted tetrahedral geometry. All the NiII ions are hexacoordinate (6 O) with a distorted octahedral geometry whereas the LnIII ion is octacoordinate (8 O) with a distorted square-antiprism geometry. All the NiII ions are connected to the central LnIII ion through μ2 bridging of one deprotonated phenolic oxygen and two deprotonated alkoxy oxygen atoms. The magnetic properties of 1–4 were investigated in the temperature range 2–300 K. The magnetic properties of 1 were fitted by using a Hamiltonian containing isotropic exchange, NiII local zero-field-splitting, and Zeeman effects (Ĥ = Ĥexchange + Ĥzfs + Ĥzeeman). The molecular structures of 1–4 reveal that the Ni–O–Ln angle is around 89° whereas the Ni–O–Ni angle is about 96°. Because of this accidental orthogonality, ferromagnetic interactions between the nearest-neighbor NiII ions and between NiII and LnIII ions have been observed. The observed J values are 0.34 and 1.88 cm–1 between GdIII–NiII and NiII–NiII, respectively.
Co-reporter:Subrata Kundu, Chandrajeet Mohapatra and Vadapalli Chandrasekhar
RSC Advances 2014 vol. 4(Issue 96) pp:53662-53664
Publication Date(Web):14 Oct 2014
DOI:10.1039/C4RA09371B
We report two hybrid inorganic ring systems in polymeric as well as monomeric forms. Both of these contain interconnected cyclophosphazene–stannoxane motifs.
Co-reporter:Vadapalli Chandrasekhar, Joydeb Goura, Kandasamy Gopal, Junjie Liu, Paul Goddard
Polyhedron 2014 72() pp: 35-42
Publication Date(Web):
DOI:10.1016/j.poly.2014.01.017
Co-reporter:Subrata Kundu;Ramesh K. Metre;Rajeev Yadav;Dr. Pratik Sen;Dr. Vadapalli Chrasekhar
Chemistry – An Asian Journal 2014 Volume 9( Issue 5) pp:1403-1412
Publication Date(Web):
DOI:10.1002/asia.201400054
Abstract
Organostannoxanes have been used as scaffolds for the preparation of multi-chromophore assemblies. A single-step synthesis procedure allows the preparation of compounds in which the number of chromophore units can be varied from two to six. Thus, the reactions of pyrene sulfonic acid (PySO3H) or C16H9CHNC6H3(COOH)2 (LH2) with various organotin precursors gave pyrene-containing organostannoxanes, that is, [Ph3SnPySO3]6 (1), [{(Me2Sn)2(μ3-O)(μ-OH)PySO3}2{(Me2Sn)2(μ3-O)(μ-OH)H2O}2⋅2 PySO3] (2), [{tBu2Sn(OH)PySO3}2] (3), [{(nBuSn)12(O)14(OH)6{PySO3}2] (4), and [{(nBu2Sn)L}3]2⋅C6H5CH3 (5). Compounds 1–5 were characterized by using X-ray crystallography. Compounds 1 and 5 are 24-membered macrocycles. Macrocycle 1 possesses intramolecular π–π stacking interactions. An unusual co-crystal of two tetrameric ladders in 2 was observed in which one of the components of the co-crystal is neutral whereas the other is dicationic and two pyrenesulfonate counterions are present to balance the overall charge. In the solid state these compounds reveal rich supramolecular structures. Photophysical studies on 1–5 reveal that interactions in the solid state lead to considerable broadening of the emission bands.
Co-reporter:Ramesh K. Metre, Subrata Kundu, Dipankar Sahoo, and Vadapalli Chandrasekhar
Organometallics 2014 Volume 33(Issue 9) pp:2380-2383
Publication Date(Web):April 30, 2014
DOI:10.1021/om5000216
The reaction of 1,1,2,3,3-pentamethyltrimethylenephosphinic acid cycP(O)OH and (C6H11)2P(O)OH with monoorganotellurium trichloride RTeCl3 (R = 2-phenylazophenyl) in benzene at room temperature afforded two pentanuclear complexes, [(RTe)4(TeO)(μ-O)6(cycPO2)2]·THF(1) [cycPO2 = 1,1,2,3,3-pentamethylene phosphinate] and [(RTe)4(TeO)(μ-O)6{(C6H11)2PO2}2]·2C6H6 (2). The reactions leading to the formation of 1 and 2 involve a Te–C bond cleavage. 1 and 2 are isostructural complexes and contain a Te4P2O6 macrocyclic framework that is part of a Te5O11P2 multi-metallacyclic framework. Both of these compounds contain a central inorganic Te═O connected to four other tellurium centers through four μ-O bridges.
Co-reporter:Vadapalli Chandrasekhar, Atanu Dey, Sourav Das, Mathieu Rouzières, and Rodolphe Clérac
Inorganic Chemistry 2013 Volume 52(Issue 5) pp:2588-2598
Publication Date(Web):February 21, 2013
DOI:10.1021/ic302614k
Sequential reaction of the multisite coordination ligand (LH3) with Cu(OAc)2·H2O, followed by the addition of a rare-earth(III) nitrate salt in the presence of triethylamine, afforded a series of heterometallic heptanuclear complexes containing a [Cu5Ln2] core {Ln = Y(1), Lu(2), Dy(3), Ho(4), Er(5), and Yb(6)}. Single-crystal X-ray crystallography reveals that all the complexes are dicationic species that crystallize with two nitrate anions to compensate the charge. The heptanuclear aggregates in 1–6 are centrosymmetrical complexes, with a hexagonal-like arrangement of six peripheral metal ions (two rare-earth and four copper) around a central Cu(II) situated on a crystallographic inversion center. An all-oxygen environment is found to be present around the rare-earth metal ions, which adopt a distorted square-antiprismatic geometry. Three different Cu(II) sites are present in the heptanuclear complexes: two possess a distorted octahedral coordination sphere while the remaining one displays a distorted square-pyramidal geometry. Detailed static and dynamic magnetic properties of all the complexes have been studied and revealed the single-molecule magnet behavior of the Dy(III) and Ho(III) derivatives.
Co-reporter:Vadapalli Chandrasekhar, Chandrajeet Mohapatra, Rahul Banerjee, and Arijit Mallick
Inorganic Chemistry 2013 Volume 52(Issue 7) pp:3579-3581
Publication Date(Web):March 13, 2013
DOI:10.1021/ic302528b
A 4-connected triorganotin 3D coordination polymer in a sqc topology has been shown to possess 1D microchannels along its crystallographic a axis. This main-group-element-containing framework structure shows selective gas adsorption, preferring CO2 and H2 over N2.
Co-reporter:Vadapalli Chandrasekhar, Prasenjit Bag, and Enrique Colacio
Inorganic Chemistry 2013 Volume 52(Issue 8) pp:4562-4570
Publication Date(Web):March 28, 2013
DOI:10.1021/ic400091j
The synthesis of a series of macrocyclic, isostructural octanuclear lanthanide complexes [Gd8 (LH2)4 (μ-Piv)4 (η2-Piv)4 (μ-OMe)4]·6CH3OH·2H2O (1), [Tb8 (LH2)4 (μ-Piv)4 (η2-Piv)4 (μ-OMe)4]4CH3OH·4H2O (2), [Dy8(LH2)4 (μ-Piv)4 (η2-Piv)4 (μ-OMe)4]·8CH3OH (3), and [Ho8(LH2)4(μ-Piv)4 (η2-Piv)4 (μ-OMe)4]·CH3OH·4H2O (4) have been achieved, using Ln(III) nitrate salts, pivalic acid, and a new multidentate chelating ligand (2E,N′E)-N′-(3-((bis(2- hydroxyethyl)amino)methyl)-2-hydroxy-5-methylbenzylidene)-2-(hydroxyimino) propane hydrazide (LH5), containing two unsymmetrically disposed arms; one side of the phenol unit is decorated with a diethanolamine group while the other side is a hydrazone that has been built by the condensation reaction involving 2-hydroxyiminopropanehydrazide. All the compounds, 1–4, are neutral and are held by the four [LH2]3– triply deprotonated chelating ligands. In these complexes all the lanthanide ions are doubly or triply bridged via phenolate, alkoxy, and pivalate oxygens. The metal centers are distributed over the 8 vertices of an octagon, resembling a cyclooctadiene ring core. The details of magnetochemical analysis for complexes 1–4 shows that they exhibit antiferromagnetic interactions between the Ln3+ ions through the phenoxo, alkoxo, and pivalato bridging groups. None of the compounds exhibits slow relaxation of the magnetization at zero applied direct current (dc) magnetic field, which could be due to the existence of a fast quantum tunneling relaxation of the magnetization (QTM). In the case of 3, the application of a small dc field is enough as to fully or partly suppress the fast and efficient zero-field QTM allowing the observation of slow relaxation above 2 K.
Co-reporter:Vadapalli Chandrasekhar, Atanu Dey, Antonio J. Mota, and Enrique Colacio
Inorganic Chemistry 2013 Volume 52(Issue 8) pp:4554-4561
Publication Date(Web):April 4, 2013
DOI:10.1021/ic400073y
The reaction of the multisite coordination ligand (LH4) with CoX2·nH2O in the presence of tetrabutylammonium hydroxide affords a series of homometallic dinuclear mixed-valence complexes, [CoIIICoII(LH2)2(X)(H2O)](H2O)m (1, X = Cl and m = 4; 2, X = Br and m = 4; 3, X = NO3 and m = 3). All of the complexes have been structurally characterized by X-ray crystallography. Both cobalt ions in these dinuclear complexes are present in a distorted-octahedral geometry. Detailed magnetic studies on 1–3 have been carried out. M vs H data at different temperatures can be fitted with S = 3/2, the best fit leading to D3/2 = −7.4 cm–1, |E/D| < 1 × 10–3, and g = 2.32 for 1 and D3/2 = −9.7 cm–1, |E/D| <1 × 10–4, and g = 2.52 for 2. In contrast to 1 and 2, M vs H data at different temperatures suggest that compound 3 has comparatively little magnetic anisotropy. In accordance with the large negative D values observed for compounds 1 and 2, they are single-molecule magnets (SMMs) and exhibit slow relaxation of magnetization at low temperatures under an applied magnetic field of 1000 Oe with the following energy barriers: 7.9 cm–1 (τo = 6.1 × 10–6 s) for 1 and 14.5 cm–1 (τo = 1.0 × 10–6 s) for 2. Complex 3 does not show any SMM behavior, as expected from its small magnetic anisotropy. The τo values observed for 1 and 2 are much larger than expected for a SMM, strongly suggesting that the quantum pathway of relaxation at very low temperatures is not fully suppressed by the effects of the applied field.
Co-reporter:Vadapalli Chandrasekhar, Prasenjit Bag, Manfred Speldrich, Jan van Leusen, and Paul Kögerler
Inorganic Chemistry 2013 Volume 52(Issue 9) pp:5035-5044
Publication Date(Web):April 24, 2013
DOI:10.1021/ic302742u
Sequential reaction of Mn(II) and lanthanide(III) salts with a new multidentate ligand, 2,2′-(2-hydroxy-3-methoxy-5-methylbenzylazanediyl)diethanol (LH3), containing two flexible ethanolic arms, one phenolic oxygen, and a methoxy group afforded heterometallic tetranuclear complexes [Mn2Dy2(LH)4(μ-OAc)2](NO3)2·2CH3OH·3H2O (1), [Mn2Gd2(LH)4(μ-OAc)2](NO3)2·2CH3OH·3H2O (2), [Mn2Tb2(LH)4(μ-OAc)2](NO3)2·2H2O·2CH3OH·Et2O (3), and [Mn2Ho2(LH)4(μ-OAc)2]Cl2·5CH3OH (4). All of these dicationic complexes possess an arch-like structural topology containing a central MnIII–Ln–Ln–MnIII core. The two central lanthanide ions are connected via two phenolate oxygen atoms. The remaining ligand manifold assists in linking the central lanthanide ions with the peripheral Mn(III) ions. Four doubly deprotonated LH2– chelating ligands are involved in stabilizing the tetranuclear assembly. A magnetochemical analysis reveals that single-ion effects dominate the observed susceptibility data for all compounds, with comparably weak Ln···Ln and very weak Ln···Mn(III) couplings. The axial, approximately square-antiprismatic coordination environment of the Ln3+ ions in 1–4 causes pronounced zero-field splitting for Tb3+, Dy3+, and Ho3+. For 1 and 3, the onset of a slowing down of the magnetic relaxation was observed at temperatures below approximately 5 K (1) and 13 K (3) in frequency-dependent alternating current (AC) susceptibility measurements, yielding effective relaxation energy barriers of ΔE = 16.8 cm–1 (1) and 33.8 cm–1 (3).
Co-reporter:Vadapalli Chandrasekhar, Joydeb Goura, and Andrew Duthie
Inorganic Chemistry 2013 Volume 52(Issue 9) pp:4819-4824
Publication Date(Web):April 16, 2013
DOI:10.1021/ic3022485
Two novel indium(III) phosphonates, [In2(t-BuPO3H)4(phen)2Cl2] (1) and [In3(C5H9PO3)2(C5H9PO3H)4(phen)3]·NO3·3.5H2O (2) with phen = 1,10-phenanthroline, have been synthesized by solvothermal reactions involving indium(III) salts and organophosphonic acids. 1 is a dinuclear compound where the two indium centers are bridged by a pair of isobidentate phosphonate ligands, [t-BuP(O)2OH]−, resulting in an eight-membered (In2P2O4) puckered ring. Compound 2 is trinuclear; the In3 platform is held together by two bicapping tripodal phosphonate ligands from the top and bottom of the indium plane. In addition, two bridging monoanionic phosphonate ligands serve to bind two pairs of indium centers. Both 1 and 2 also contain monodentate monoanionic phosphonate ligands. The solid-state MAS 31P NMR spectrum of complex 1 shows two signals at 21.9 and 29.3 ppm. Compound 2 contains signal maxima at 25.8 and 28.9 ppm, with a shoulder at 31.5 ppm. Room temperature solid-state fluorescence spectra of 1 and 2 are characterized by strong emission bands at 385 nm (λex = 350 nm) and 395 nm (λex = 350 nm), respectively, which are red-shifted with respect to the emission of free phenanthroline.
Co-reporter:Vadapalli Chandrasekhar, Sakiat Hossain, Sourav Das, Sourav Biswas, and Jean-Pascal Sutter
Inorganic Chemistry 2013 Volume 52(Issue 11) pp:6346-6353
Publication Date(Web):May 16, 2013
DOI:10.1021/ic302848k
The reaction of a new hexadentate Schiff base hydrazide ligand (LH3) with rare earth(III) chloride salts in the presence of triethylamine as the base afforded two planar tetranuclear neutral complexes: [{(LH)2Dy4}(μ2-O)4](H2O)8·2CH3OH·8H2O (1) and [{(LH)2Ho4}(μ2-O)4](H2O)8·6CH3OH·4H2O (2). These neutral complexes possess a structure in which all of the lanthanide ions and the donor atoms of the ligand remain in a perfect plane. Each doubly deprotonated ligand holds two Ln(III) ions in its two distinct chelating coordination pockets to form [LH(Ln)2]4+ units. Two such units are connected by four [μ2-O]2– ligands to form a planar tetranuclear assembly with an Ln(III)4 core that possesses a rhombus-shaped structure. Detailed static and dynamic magnetic analysis of 1 and 2 revealed single-molecule magnet (SMM) behavior for complex 1. A peculiar feature of the χM″ versus temperature curve is that two peaks that are frequency-dependent are revealed, indicating the occurrence of two relaxation processes that lead to two energy barriers (16.8 and 54.2 K) and time constants (τ0 = 1.4 × 10–6 s, τ0 = 7.2 × 10–7 s). This was related to the presence of two distinct geometrical sites for Dy(III) in complex 1.
Co-reporter:Vadapalli Chandrasekhar ; Prasenjit Bag ; Wolfgang Kroener ; Klaus Gieb ;Paul Müller
Inorganic Chemistry 2013 Volume 52(Issue 22) pp:13078-13086
Publication Date(Web):November 7, 2013
DOI:10.1021/ic4019025
The reaction between Ln(III) chloride and NiCl2·4H2O salts in presence of a multidentate sterically unencumbered ligand, (E)-2,2′-(2-hydroxy-3-((2-hydroxyphenylimino)methyl)-5-methylbenzylazanediyl)diethanol (LH4) leads to the synthesis of four isostructural pentanuclear hetereometallic complexes [Ni2Dy3(LH)4]Cl (1), [Ni2Gd3(LH)4]Cl (2), [Ni2Tb3(LH)3(LH2)]Cl2 (3), [Ni2 Ho3 (LH)3 (LH2)]Cl2 (4) with unprecedented topology. Here the two compounds 1 are 2 are monocationic and crystallize in chiral space group, P212121 whereas compounds 3 and 4 are dicationic and crystallize in achiral space group P21/n. The total metal framework, {Ni2Ln3} unit is held by four triply deprotonated ligands [LH]3– in 1 and 2 whereas in case of 3 and 4 three triply deprotonated [LH]3– and one doubly deprotonated [LH2]2– ligands are involved. In these complexes both the lanthanide ions and the nickel(II) ions are doubly bridged and the bridging is composed of oxygen atoms derived from either phenolate or ethoxide groups. The analysis of SQUID measurements reveal a high magnetic ground state and a slow relaxation of the magnetization with two relaxation regimes for 1. For the thermally activated regime we found an effective energy barrier of Ueff = 85 K. Micro Hall probe loop measurements directly proof the single-molecule magnet (SMM) nature of 1 with a blocking temperature of TB = 3 K and an open hysteresis for sweep rates faster than 50 mT/s.
Co-reporter:Vadapalli Chandrasekhar ; Sourav Das ; Atanu Dey ; Sakiat Hossain ;Jean-Pascal Sutter
Inorganic Chemistry 2013 Volume 52(Issue 20) pp:11956-11965
Publication Date(Web):October 10, 2013
DOI:10.1021/ic401652f
The reaction of the lanthanide(III) salts [Dy(III), Tb(III), and Gd (III)] with a hetero donor chelating ligand N′-(2-hydroxy-3-methoxybenzylidene)-6-(hydroxymethyl) picolinohydrazide (LH3) and pivalic acid (PivH) in the presence of tetra-n-butylammonium hydroxide (TBAH) afforded the tetranuclear Ln(III) coordination compounds, [Ln4(LH)2(LH2)2(μ2-η1η1Piv)2(η1Piv)4]·2CHCl3 [Ln = Dy(1), Tb(2), and Gd(3)]. The molecular structure of these complexes reveals that the tetranuclear derivatives are composed of two dinuclear subunits which are interconnected through the coordination action of the picolinoyl hydrazine ligand. Within each subunit two different types of Ln(III) ions are present. One of these is eight-coordinate in a distorted triangular dodecahedral geometry while the other is nine-coordinate in a distorted spherical capped square antiprism geometry. Alternating current (ac) susceptibility measurements of complex 1 reveal a frequency- and temperature-dependent two step out-of-phase signals under 1kOe DC field which is characteristic of a single-molecule magnet (SMM) behavior. Analysis of the magnetic data afforded the anisotropic barriers and relaxation times: Δ/kB = 62.6 K, τ0 = 8.7 × 10–7 s; Δ/kB = 26.3 K, τ0 = 1.26 × 10–6 s for the slow and fast relaxations respectively.
Co-reporter:Vadapalli Chandrasekhar, Dipankar Sahoo and Ramesh K. Metre
CrystEngComm 2013 vol. 15(Issue 37) pp:7419-7422
Publication Date(Web):11 Jul 2013
DOI:10.1039/C3CE40997J
Two pairs of isomorphic molecular phosphonates are reported. The first isomorphic pair involves the co-crystals [{Co2(η1-DMPzH)4(Cl3CPO3)2}{Co(η1-DMPzH)2Cl2}2](toluene)2 [1] and [{Zn2(η1-DMPzH)4(Cl3CPO3)2}{Zn(η1-DMPzH)2Cl2}2](toluene)2 [2] while the second isomorphic pair is {Co2(η1-DMPzH)2Cl2(Cl3CPO3)2}(HNEt3)2 [3] and {Zn2(η1-DMPzH)2Cl2(Cl3CPO3)2}(HNEt3)2 [4]. These have been prepared by multi-component reactions involving normal solution-state synthesis at room temperature. Change of reaction solvent from acetonitrile to methanol affords change of products from 1 and 2 to 3 and 4.
Co-reporter:Vadapalli Chandrasekhar, Subrata Kundu, Jitendra Kumar, Sandeep Verma, Kandasamy Gopal, Amaresh Chaturbedi, and Kuppuswamy Subramaniam
Crystal Growth & Design 2013 Volume 13(Issue 4) pp:1665-1675
Publication Date(Web):February 15, 2013
DOI:10.1021/cg3018776
The reactions of 3-(N9-adeninyl) propanoic acid (LH) with various di- and triorganotin oxides have been investigated. Thus, the reaction of di-tert-butyltin oxide (t-Bu2SnO)3 in a 3:1 ratio afforded the dinuclear derivative [t-Bu2Sn(μ-OH)L]2·7H2O (1). A similar reaction involving bis(tri-n-butyltin)oxide, (n-Bu3Sn)2O, in a 2:1 ratio afforded the one-dimensional (1D) coordination polymer [n-Bu3SnL·0.33H2O]n (2). Similarly the reaction with (n-Bu2SnO)n in a 2:1 ratio afforded the tetranuclear [{n-Bu2Sn}2(μ3-O)(μ-OH)L]2 (3). On the other hand, a similar reaction in a 1:1 ratio also gave the tetranuclear product [{n-Bu2Sn}2(μ3-O)L2]2 (4). The molecular structure of 1reveals a central dinuclear Sn2O2 motif where the two tin centers are bridged by two μ-OH groups. Each tin is bound with a monodentate carboxylate group; the C═O unit of these carboxylates is involved in an intramolecular hydrogen bonding with the bridging OH unit. The supramolecular structure of 1 reveals the formation of a 1D zigzag chain mediated by intermolecular hydrogen bonding interaction through the Watson-Crick or the Hoogsteen faces. 2 is a 1D coordination polymer formed by the successive bridging of triorganotin units by the carboxylate ligand L. The supramolecular structure of 2 reveals that two 1D coordination polymers interact to generate novel adenine homotrimers formed as a result of alternating Watson-Crick–Watson-Crick and Hoogsteen–Watson-Crick interactions. The molecular structures of 3 and 4 reveal them to be tetranuclear possessing a ladder-like structure. The essential difference between their molecular structures is that in 4 there are four carboxylate ligands, while in 3 there are only two. Both of these complexes reveal intramolecular and intermolecular hydrogen bonding and π···π stacking interactions. The nematicidal activity of 1–3 was examined against Caenorhabditis elegans. Compound 2 was found to be highly active, effecting a high mortality even at very low concentrations such as 25 or 10 ppm.
Co-reporter:Vadapalli Chandrasekhar, Chandrajeet Mohapatra, and Ramesh K. Metre
Crystal Growth & Design 2013 Volume 13(Issue 10) pp:4607-4614
Publication Date(Web):August 29, 2013
DOI:10.1021/cg401201w
The reaction of (n-Bu3Sn)2O with (E)-5-(pyridin-4-yl-methyleneamino)isophthalic acid (LH2) in a stoichiometric ratio of 1:1 resulted in the formation of a 2D coordination polymer [(n-Bu3Sn)2(μ-L)]n (1). The structure of 1 contains a 36-membered macrocycle as its repeating building block. The reactions of Me3SnCl or (Ph3Sn)2O with LH2, on the other hand, result in the generation of [(Me3Sn)2(μ-L)(H2O)]n (a neutral 1D coordination polymer) (2) and [(Ph3Sn)(μ-L)(Et3NH)]n (an anionic 1D coordination polymer) (3), respectively. Compounds 1–3 show a rich supramolecular architecture in their solid state as a result of multiple secondary interactions.
Co-reporter:Vadapalli Chandrasekhar and Chandrajeet Mohapatra
Crystal Growth & Design 2013 Volume 13(Issue 11) pp:4655-4658
Publication Date(Web):October 10, 2013
DOI:10.1021/cg401363p
A two-dimensional coordination polymer [(n-Bu3Sn)4(μ-L)2(4,4′-bipy)]n (1) was prepared in a reaction between (n-Bu3Sn)2O, (E)-5-(pyridin-4-yl-methyleneamino)isophthalic acid (LH2), and 4,4′-bipyridine (4,4′-bipy). The structure of 1 is built by the interlinking of 82-membered macrocyles. The generation of the 2D coordination polymer is facilitated by the multisite coordination capability of the dianionic ligand (L2–) as well as involvement of 4,4′-bipyridine as an ancillary ligand.
Co-reporter:Vadapalli Chandrasekhar, Prasenjit Bag, Balasubramanian Murugesapandian and Mrituanjay D. Pandey
Dalton Transactions 2013 vol. 42(Issue 43) pp:15447-15456
Publication Date(Web):12 Aug 2013
DOI:10.1039/C3DT51431E
The sequential reaction of a phosphorus-based trishydrazone ligand, LH3 with anhydrous ZnCl2 and LnCl3·6H2O in a 2:2:1 stoichiometric ratio in the presence of triethylamine as the base leads to the formation of monocationic trinuclear complexes [L2Zn2Ln]Cl {Ln = Gd (1), Tb (2), Nd (3), Eu (4) and L = [(S)P[N(Me)NCH–C6H3-2-O-3-OMe]3}. All the three metal ions, in each of these compounds, are arranged in a linear fashion. The two terminal Zn(II) ions are encapsulated by three imino and three phenolate oxygen atoms while the lanthanide ion remains in the centre with an all-oxygen coordination environment. Detailed photophysical measurements reveal the complete absence of antenna sensitization in all the four complexes. However, a strong emission was found for 2 and 4 when excited directly at their f–f levels.
Co-reporter:Vadapalli Chandrasekhar, Dipankar Sahoo, Ramakirushnan Suriya Narayanan, Raymond J. Butcher, Franscesc Lloret and Emilio Pardo
Dalton Transactions 2013 vol. 42(Issue 23) pp:8192-8196
Publication Date(Web):25 Apr 2013
DOI:10.1039/C3DT00103B
Structure and characterization of [Cu26{2,3,5,6-(Me)4C6H-CH2-PO3}18(μ2-OH)4(μ3-OH)6(μ4-Cl)6(μ-OH2)2(OH2)2(MeCN)4]·6MeCN·15H2O (1) is reported. Complex 1 is the largest discrete molecular homometallic transition metal phosphonate assembly. Remarkably, this gigantic molecular phosphonate has been prepared at room temperature using a normal solution synthetic method.
Co-reporter:Vadapalli Chandrasekhar and Ramakirushnan Suriya Narayanan
Dalton Transactions 2013 vol. 42(Issue 18) pp:6619-6632
Publication Date(Web):15 Feb 2013
DOI:10.1039/C3DT33084B
Pyridyloxy cyclophosphazenes, spiro-N3P3(O2C12H8)(O-C5H4N-3)4 (L1), dispiro-N3P3(O2C12H8)2(O-C5H4N-3)2 (L2) and dispiro-N3P3(O2C12H8)2(O-C5H4N-4)2 (L3) were prepared and characterized. The crystal structure of L1 was determined which showed that the cyclophosphazene ring is planar. The reaction of L1 with anhydrous copper(II) chloride or silver nitrate afforded L2M4 metallamacrocycles [{L1}2{ClCu(μ-Cl)2CuCl}]2·8CHCl3 (3) and [{L1}2{(DMF)0.5(NO3)0.5Ag}2{Ag(μ2-(O)NO2)(H2O)}2]{μ-[NO3]}·CH3OH (4) respectively. The molecular structure of 3 reveals that two CuCl2 dimers are bridged to each other in a complex metallamacrocycle that involves four metal ions and two ligands. The molecular structure of 4 is similar to that of 3 except for the presence of weak argentophilic interactions between the two Ag(I) centers. Also, a nitrate anion, which is trapped in the centre of the tetrameric assembly, assists in holding two Ag(I) ions together and 4 serves as a single source precursor for silver nanoparticles. The reaction L1 with ZnCl2 and Cd(NO3)2·4H2O afforded the 1D-coordination polymers [{L1}{ZnCl2}2]n·2nCH3OH·2nH2O (5) and [{L1}2{Cd(CH3OH)2(NO3)2}2{Cd(NO3)2(H2O)}]n·3nCH3OH·3nH2O (6) respectively. While in 5 the 20-membered macrocycles are inter-connected directly, in 6 they are bridged by a Cd(II) connector. The reaction of L2 with CoCl2 afforded the 1D-coordination polymer [{L2}2{CoCl2}]n·2nCHCl3 (7) which also contains interconnected 20-membered metallamacrocycles. On the other hand, the reaction of L2 with CuCl2 afforded [{L2}2{ClCu(μ-Cl)}2]n·2nCHCl3·nH2O (8) which is a 1D-coordination polymer that contains {ClCu(μ-Cl)2CuCl} units. The reaction of L3 with CuCl2 and Cd(NO3)2·4H2O afforded [{L3}2{CuCl2}]n·nDMF (9) and [{L3}2{Cd(NO3)2}]n·nCHCl3·nCH2Cl2·nH2O (10) respectively. While 9 is a 2D-coordination polymer containing 48-membered metallamacrocycles, 10 is a 1D-coordination polymer containing interconnected 24-membered metallamacrocycles which possess spirocyclic cadmium ions as nodes.
Co-reporter:Vadapalli Chrasekhar;Sourav Das;Atanu Dey;Sakiat Hossain;Francesc Lloret;Emilio Pardo
European Journal of Inorganic Chemistry 2013 Volume 2013( Issue 25) pp:4506-4514
Publication Date(Web):
DOI:10.1002/ejic.201300413
Abstract
The reaction of 6-formyl-2-(hydroxymethyl)-4-methylphenol (LH2) with appropriate lanthanide salts followed by reaction with Co(OAc)2·4H2O afforded the pentanuclear heterobimetalllic compounds [Co4Ln(L)4(OAc)2(S)4](NO3)(S) [LnIII = GdIII, S = MeOH (1); LnIII = DyIII, S = H2O (2); LnIII = TbIII, S = MeOH (3); LnIII = HoIII, S = MeOH (4)] in good yields. All the compounds are stable in solution as confirmed by ESI-MS studies. These complexes contain a distorted Co4 tetrahedral core, which encapsulates a central lanthanide ion. The CoII and LnIII ions are in an all-oxygen environments. All the CoII ions possess a distorted octahedral geometry, and the LnIII ions are in a distorted square-antiprismatic geometry. The magnetic properties of 1–4 have been investigated in the temperature range 2–300 K. In addition, the magnetic properties of 1 were fitted by using a Hamiltonian of the type H = HSO + Haxial + Hexchange + HZeeman. A moderately strong antiferromagnetic interaction between the nearest-neighbour CoII ions was found, whereas the magnetic interaction between the CoII ions and the corresponding LnIII ions is negligible.
Co-reporter:Vadapalli Chandrasekhar, Ramesh K. Metre, and Sourav Biswas
Organometallics 2013 Volume 32(Issue 11) pp:3419-3422
Publication Date(Web):May 17, 2013
DOI:10.1021/om400346b
The reactions of RSnCl3 (1; R = 2-(phenylazo)phenyl) with FcCOOH or di-tert-butyl phosphate in refluxing THF afforded the monoorganodistannoxanes [(RSn)2(μ2-O)(μ2-FcCOO)2(η-FcCOO)2]·THF (2) and {(RSn)2(μ2-O)[(t-BuO)2PO2]2Cl2}·THF·2H2O (3). The molecular structure of 2 contains seven-coordinate tin centers in a distorted-pentagonal-bipyramidal geometry, while 3 contains six-coordinate tin centers in a distorted-octahedral geometry. In the dinuclear compounds 2 and 3 the two tin centers are bridged by a μ2-O unit, affording a rare Sn–O–Sn motif among monoorganostannoxanes. In addition, each tin is also intramolecularly coordinated to the nitrogen atom of the 2-phenylazophenyl substituent (N→Sn). Further, in 2, the two tin centers are bridged by two isobidentate ferrocenecarboxylate ligands; each tin center also is bound to a chelating ferrocenecarboxylate ligand. On the other hand, in 3, while the two tin centers are bridged by two isobidentate di-tert-butyl phosphate ligands, each tin center also has a terminal chloride ligand.
Co-reporter:Saurabh Kumar Singh, Thayalan Rajeshkumar, Vadapalli Chandrasekhar, Gopalan Rajaraman
Polyhedron 2013 66() pp: 81-86
Publication Date(Web):
DOI:10.1016/j.poly.2013.02.037
Co-reporter:Vadapalli Chandrasekhar ; Loganathan Nagarajan ; Sakiat Hossain ; Kandasamy Gopal ; Surajit Ghosh ;Sandeep Verma
Inorganic Chemistry 2012 Volume 51(Issue 10) pp:5605-5616
Publication Date(Web):May 10, 2012
DOI:10.1021/ic202510d
A multicomponent synthetic strategy involving copper(II) ions, tert-butylphosphonic acid (t-BuPO3H2) and 3-substituted pyrazole ligands has been adopted for the synthesis of soluble molecular copper(II) phosphonates. The use of six different 3-substituted pyrazoles, 3-R-PzH [R = H, Me, CF3, Ph, 2-pyridyl (2-Py), and 2-methoxyphenyl (2-MeO-C6H4)] as ancillary ligands afforded nine different decanuclear cages, [Cu5(μ3-OH)2(O3P-t-Bu)3(3-R-Pz)2(X)2]2·(Y) where R = H, X = t-BuPO3H, and Y = (Et3NH+)4(solvent) (1); R = Me, X = 3-MePzH, and Y = solvent (2); R = Me, X = t-BuPO3H, and Y = (Et3NH+)4(solvent) (3); R = CF3, X = t-BuPO3H, and Y = (Et3NH+)4(solvent) (4); R = Ph, X = 3-PhPzH, and Y = solvent (5); R = 2-Py, X = 0.5 MeOH, and Y = solvent (6); R = 2-Py, X = none, and Y = solvent (7); R = 2-Py, X = H2O, and Y = (Et3NH+·PF6–)2(solvent) (8); R = 2-MeO-C6H4, X = MeOH or 0.5:0.5 MeOH/H2O, and Y = solvent (9). Compounds 1–6, 8, and 9 were isolated using a direct synthetic method which involves the reaction of copper(II) salts and the ligands, while 7 was obtained from an indirect route involving the reaction of preformed copper-pyridylpyrazolate precursor complexes and t-BuPO3H2. The decametallic compounds 1–9 possess a butterfly shaped core. The core of the cages 1, 3, and 4 are tetraanionic and contain more phosphonates than pyrazole ligands, while the other cages are neutral and contain more pyrazoles than phosphonate ligands. Compounds 1–6 have been studied by electrospray ionization-high-resolution mass spectrometry (ESI-HRMS). The decanuclear cage 6 was shown to be a good plasmid modifier.
Co-reporter:Vadapalli Chandrasekhar, Bani Mahanti, Priyanka Bandipalli, and Kotamarthi Bhanuprakash
Inorganic Chemistry 2012 Volume 51(Issue 20) pp:10536-10547
Publication Date(Web):September 26, 2012
DOI:10.1021/ic300694m
The reaction of the cyclometalated chloro-bridged iridium(III) dimers [(ppy)2 Ir(μ-Cl)]2 (ppyH = 2-phenyl pyridine) and [(tpy)2Ir(μ-Cl)]2 (tpyH = 2-p-tolylpyridine) with 3,5-diphenylpyrazole (Ph2PzH) in the presence of sodium methoxide resulted in the formation of heterobridged dimers [(ppy)2Ir(μ-OH)(μ-Ph2Pz)Ir(ppy)2] (1) and [(tpy)2Ir(μ-OH)(μ-Ph2Pz)Ir(tpy)2] (2). Interestingly, the reaction of [(ppy)2Ir(μ-Cl)]2 with 3(5)-methyl-5(3)-phenylpyrazole (PhMePzH) afforded both a heterobridged dimer, [(ppy)2Ir(μ-OH)(μ-PhMePz)Ir(ppy)2] (3), and the monomer [(ppy)2Ir(PhMePz)Cl] (4). The compound [(ppy)2Ir(PhMePz)OH] (5) containing a terminal OH was obtained in a hydrolysis reaction involving 4, sodium methoxide, and PhMePzH. Complexes 1–5 were characterized by X-ray crystallography and electrospray ionization high-resolution mass spectrometry. All of the complexes are luminescent at room temperature in their dichloromethane solutions. The luminescence of the dinuclear complexes is characterized by a single structureless band centered at λmax = 550 nm (1 and 3) and 546 nm (2). The emission spectra of the mononuclear complexes 4 and 5 display vibronic structures with their λmax values at 497 nm (4) and 513 nm (5). In each case, the main emission bands are accompanied by shoulder bands at 526 (4) and 534 nm (5). The quantum yields, calculated with reference to [Ir(ppy)2(bpy)]PF6 (ΦCH3CN = 0.0622), range from 0.11 to 0.17 for the dinuclear complexes and 0.045 to 0.048 for the mononuclear complexes. The lifetimes of the emission are in the microsecond region, suggesting the phosphorescent nature of the emission. Density functional theory (DFT) and time-dependent DFT calculations were performed on complexes 1 and 4 in the ground state to gain insight into the structural, electronic, and photophysical properties. Electrochemical studies on complexes 1–3 showed the presence of two consecutive one-electron-oxidation processes, assigned as the stepwise oxidation of the two IrIII centers, i.e., IrIII–IrIII/IrIII–IrIV and IrIII–IrIV/IrIV–IrIV couples, respectively. The monomers displayed single-oxidation peaks. No reduction process was observed within the solvent cathodic potential limit.
Co-reporter:Vadapalli Chandrasekhar, Sourav Das, Rajeev Yadav, Sakiat Hossain, Rashmi Parihar, Ganesh Subramaniam, and Pratik Sen
Inorganic Chemistry 2012 Volume 51(Issue 16) pp:8664-8666
Publication Date(Web):August 6, 2012
DOI:10.1021/ic301399a
A new water-soluble, multisite-coordinating ligand LH7 was prepared by the condensation of tris(hydroxymethyl)aminomethane with 2,6-diformyl-p-cresol. LH7 is a selective chemosensor for Cu2+, under physiological conditions, with visual detection limits of 20 ppm (ambient light conditions) and 4 ppm (UV light conditions). LH7 can also be used in biological cell lines for the detection of Cu2+.
Co-reporter:Vadapalli Chandrasekhar, Tanima Hajra, Jitendra K. Bera, S.M. Wahidur Rahaman, Nisa Satumtira, Oussama Elbjeirami, and Mohammad A. Omary
Inorganic Chemistry 2012 Volume 51(Issue 3) pp:1319-1329
Publication Date(Web):January 18, 2012
DOI:10.1021/ic2012952
Metallamacrocycles 1, 2, and 3 of the general formula [{Ir(ppy)2}2(μ-BL)2](OTf)2 (ppyH = 2-phenyl pyridine; BL = 1,2-bis(4-pyridyl)ethane (bpa) (1), 1,3-bis(4-pyridyl)propane (bpp) (2), and trans-1,2-bis(4-pyridyl)ethylene (bpe) (3)) have been synthesized by the reaction of [{(ppy)2Ir}2(μ-Cl)2], first with AgOTf to effect dechlorination and later with various bridging ligands. Open-frame dimers [{Ir(ppy)2}2(μ-BL)](OTf)2 were obtained in a similar manner by utilizing N,N′-bis(2-pyridyl)methylene-hydrazine (abp) and N,N′-(bis(2-pyridyl)formylidene)ethane-1,2-diamine (bpfd) (for compounds 4 and 5, respectively) as bridging ligands. Molecular structures of 1, 3, 4, and 5 were established by X-ray crystallography. Cyclic voltammetry experiments reveal weakly interacting “Ir(ppy)2” units bridged by ethylene-linked bpe ligand in 3; on the contrary the metal centers are electronically isolated in 1 and 2 where the bridging ligands are based on ethane and propane linkers. The dimer 4 exhibits two accessible reversible reduction couples separated by 570 mV indicating the stability of the one-electron reduced species located on the diimine-based bridge abp. The “Ir(ppy)2” units in compound 5 are noninteracting as the electronic conduit is truncated by the ethane spacer in the bpfd bridge. The dinuclear compounds 1–5 show ligand centered (LC) transitions involving ppy ligands and mixed metal to ligand/ligand to ligand charge transfer (MLCT/LLCT) transitions involving both the cyclometalating ppy and bridging ligands (BL) in the UV–vis spectra. For the conjugated bridge bpe in compound 3 and abp in compound 4, the lowest-energy charge-transfer absorptions are red-shifted with enhanced intensity. In accordance with their similar electronic structures, compounds 1 and 2 exhibit identical emissions. The presence of vibronic structures in these compounds indicates a predominantly 3LC excited states. On the contrary, broad and unstructured phosphorescence bands in compounds 3–5 strongly suggest emissive states of mixed 3MLCT/3LLCT character. Density functional theory (DFT) calculations have been carried out to gain insight on the frontier orbitals, and to rationalize the electrochemical and photophysical properties of the compounds based on their electronic structures.
Co-reporter:Vadapalli Chandrasekhar ; Tapas Senapati ; Atanu Dey ; Sourav Das ; Marguerite Kalisz ;Rodolphe Clérac
Inorganic Chemistry 2012 Volume 51(Issue 4) pp:2031-2038
Publication Date(Web):February 9, 2012
DOI:10.1021/ic201463g
The carbophosphazene and cyclophosphazene hydrazides, [{NC(N(CH3)2)}2{NP{N(CH3)NH2}2}] (1) and [N3P3(O2C12H8)2{N(CH3)NH2}2] were condensed with o-vanillin to afford the multisite coordination ligands [{NC(N(CH3)2)}2{NP{N(CH3)N═CH-C6H3-(o-OH)(m-OCH3)}2}] (2) and [{N2P2(O2C12H8)2}{NP{N(CH3)N═CH-C 6H3-(o-OH)(m-OCH3)}2}] (3), respectively. These ligands were used for the preparation of heterometallic complexes [{NC(N(CH3)2)}2{NP{N(CH3)N═CH-C6H3-(o-O)(m-OCH3)}2}{CuCa(NO3)2}] (4), [{NC(N(CH3)2)}2{NP{N(CH3)N═CH-C6H3-(o-O)(m-OCH3)}2}{Cu2Ca2(NO3)4}]·4H2O (5), [{NC(N(CH3)2)}2{NP{N(CH3)N═CH-C6H3-(o-O)(m-OCH3)}2}{CuDy(NO3)4}]·CH3COCH3 (6), [{NP(O2C12H8)}2{NP{N(CH3)N═CH-C6H3-(o-O)(m-OCH3)}2}{CuDy(NO3)3}] (7), and [{NP(O2C12H8)}2{NP{N(CH3)N═CH-C6H3-(o-O)(m-OCH3)}2}{CuTb(NO3)3}] (8). The molecular structures of these compounds reveals that the ligands 2 and 3 possess dual coordination pockets which are used to specifically bind the transition metal ion and the alkaline earth/lanthanide metal ion; the Cu2+/Ca2+, Cu2+/Tb3+, and Cu2+/Dy3+ pairs in these compounds are brought together by phenoxide and methoxy oxygen atoms. While 4, 6, 7, and 8 are dinuclear complexes, 5 is a tetranuclear complex. Detailed magnetic properties on 6–8 reveal that these compounds show weak couplings between the magnetic centers and magnetic anisotropy. However, the ac susceptibility experiments did not reveal any out of phase signal suggesting that in these compounds slow relaxation of magnetization is absent above 1.8 K.
Co-reporter:Vadapalli Chandrasekhar, Chandrajeet Mohapatra, and Ray J. Butcher
Crystal Growth & Design 2012 Volume 12(Issue 6) pp:3285-3295
Publication Date(Web):May 18, 2012
DOI:10.1021/cg3004189
The reaction of (n-Bu3Sn)2O with pyridine-2,6-dicarboxylic acid (L1H2) in a 1:1 ratio resulted in the formation of a one-dimensional (1D) coordination polymer [(n-Bu3Sn)2(n-Bu2Sn)2(μ-L1)2(μ-OH)2]n (1). The formation of 1 is accompanied by a Sn–butyl bond cleavage reaction involving half of the organotin units. The formation of the 1D coordination polymer is facilitated by the multisite coordination capability of the dianionic ligand L1. The reaction of (n-Bu3Sn)2O with pyridine-2,5-dicarboxylic acid (L2H2) or pyridine-3,5-dicarboxylic acid (L3H2), on the other hand, results in the generation of the two-dimensional (2D) coordination polymers [(n-Bu3Sn)2(μ-L2)]n (2) and [(n-Bu3Sn)4(μ-L3)2]n (3), respectively. The formation of 2 and 3 emphasizes the importance of the relative orientation of the coordinating units in the multisite coordination ligand. Compounds 1–3 show a rich supramolecular architecture in their solid state as a result of multiple secondary interactions. Investigation of the fate of the reactions of (n-Bu3Sn)2O with pyridine dicarboxylic acids in the presence of a bridging ligand was carried out. In all the cases when the reactions were carried out in the presence of 4,4′-bipyridine (4,4′-bipy), 1D coordination polymers [(n-Bu3Sn)2(μ-L1)(μ-4,4′-bipy)]n (4), [(n-Bu3Sn)2(μ-L3)(μ-4,4′-bipy)]n (5), and [(n-Bu3Sn)2(μ-L2)(μ-4,4′-bipy)]n (6) are formed. In these cases, the 4,4′-bipyridine ligand serves as one of the connectors that link the organotin units. Interestingly, in the presence of 4,4′-bipyridine, Sn–butyl bond cleavage does not take place. While the 1D coordination polymers 4 and 5 form three-dimensional supramolecular architectures in their solid state, compound 6 possesses a 2D supramolecular architecture.
Co-reporter:Vadapalli Chandrasekhar and Ramesh K. Metre
Dalton Transactions 2012 vol. 41(Issue 38) pp:11684-11691
Publication Date(Web):16 Jul 2012
DOI:10.1039/C2DT31153D
The reaction of ferrocenedicarboxylic acid with triphenylbismuth in a 1:1 ratio under solvothermal conditions afforded the 1D coordination polymer [Bi2(μ2-η2-OOCFcCOO-μ2-η2)(η2-OOCFcCOO-η2)(μ2-η2-OOCFcCOO-η2)]n (1). In this polymer two types of bismuth centers (hepta- and octacoordinate) are present and are interconnected by the bridging coordination of ferrocene dicarboxylate ligands. The reaction of ferrocenecarboxylic acid with triphenylbismuth in a 1:3 ratio, in toluene, under refluxing conditions, afforded the 1D coordination polymer [Bi(μ2-η2-FcCOO)(η2-FcCOO)2]n (2). In the solid state, 2 exists as a helical polymer, where the inner bismuth chain is enclosed by an external sheath of ferrocene carboxylate ligands. In solution, however, 2 decomposes into the monomeric repeat unit [Bi(FcCOO)3] which is indicated by ESI-MS as well as cyclic voltammetric studies. Thus, a single, quasi-reversible redox event is seen for 2 in solution. The reaction of triphenylbismuth with ferrocenecarboxylic acid in a 1:1 stoichiometry afforded the molecular dimer [Bi2(μ2-η2-FcCOO)2(η2-FcCOO)4(H2O)4]·(2FcCOOH) (3). Compounds 1–3 reveal rich supramolecular architectures in the solid state as a result of the presence of C–H⋯O, C–H⋯π and π⋯π interactions.
Co-reporter:Vadapalli Chandrasekhar ; Tapas Senapati ; Atanu Dey ;E. Carolina Sañudo
Inorganic Chemistry 2011 Volume 50(Issue 4) pp:1420-1428
Publication Date(Web):January 20, 2011
DOI:10.1021/ic101982c
The reactions of the dinuclear copper complexes [Cu2(L)(OAc)] [H3L = N,N′-(2-hydroxypropane-1,3-diyl)bis(salicylaldimine) or [Cu2(L′)(OAc)] (H3L′ = N,N′-(2-hydroxypropane-1,3-diyl)bis(4,5-dimethylsalicylaldimine)] with various phosphonic acids, RPO3H2 (R= t-Bu, Ph, c-C5H9, c-C6H11 or 2,4,6-i-Pr3-C6H2), leads to the replacement of the acetate bridge affording tetranuclear copper(II) phosphonates, [Cu4(L)2(t-BuPO3)](CH3OH)2(C6H6) (1), [Cu4(L)2(PhPO3)(H2O)2(NMe2CHO)](H2O)2 (2), [Cu4(L′)2(C5H9PO3)](CH3OH)2 (3), [Cu4(L′)2(C6H11PO3](MeOH)4(H2O)2 (4) and [Cu4(L′)2(C30H46P2O5)](PhCH3) (5). The molecular structures of 1−4 reveal that a [RPO3]2− ligand is involved in holding the four copper atoms together by a 4.211 coordination mode. In 5, an in situ formed [(RPO2)2O]4− ligand bridges two pairs of the dinuclear subunits. Magnetic studies on these complexes reveal that the phosphonate ligand is an effective conduit for magnetic interaction among the four copper centers present; a predominantly antiferromagnetic interaction is observed at low temperatures.
Co-reporter:Vadapalli Chandrasekhar ; Venkatasubbiah Krishnan ; Ramachandran Azhakar ; Tapas Senapati ; Atanu Dey ;R. Suriya Narayanan
Inorganic Chemistry 2011 Volume 50(Issue 6) pp:2568-2579
Publication Date(Web):February 16, 2011
DOI:10.1021/ic102415x
Carbophosphazene-based coordination ligands [{NC(NMe2)}2{NP(3,5-Me2Pz)2}] (1), [{NC(NEt)2}{NC(3,5-Me2Pz)}{NP(3,5-Me2Pz)2}] (2), [NC(3,5-Me2Pz)]2[NP(3,5-Me2Pz)2] (3), [{NCCl}2{NP(NC(NMe2)2)2}] (4), and [{NC(p-OC5H4N)}2{NP(NC(NMe2)2)2}] (5) were synthesized and structurally characterized. In these compounds, the six-membered C2N3P ring is perfectly planar. The reaction of 1 with CuCl2 afforded [{NC(NMe2)}2{NHP(O)(3,5-Me2Pz)}·{Cu(3,5-Me2PzH)2(Cl)}][Cl] (6). The ligand binds to Cu(II) utilizing the geminal [P(O)(3,5-Me2Pz)] coordinating unit. Similarly, the reaction of 2 with PdCl2 afforded, after a metal-assisted P−N hydrolysis, [{NC(NEt)2}{NC(3,5-Me2Pz)}{NP(O)(3,5-Me2Pz)}·{Pd(3,5-Me2PzH)(Cl)}] (7). In the latter, the [P(O)(3,5-Me2Pz)] unit does not coordinate; in this instance, the Pd(II) is bound by a ring nitrogen atom and a carbon-tethered pyrazolyl nitrogen atom. The reaction of 3 with PdCl2 also results in P−N bond hydrolysis affording [{NC(3,5-Me2Pz)2}{NP(O)(3,5-Me2Pz)}{Pd(Cl)}] (8). In contrast to 7, however, in 8, the Pd(II) elicits a nongeminal η3 coordination from the ligand involving two carbon-tethered pyrazolyl groups and a ring nitrogen atom. Metalated products could not be isolated in the reaction of 3 with K2PtCl4. Instead, a P−O−P bridged carbodiphosphazane dimer, [{NC(3,5-Me2Pz)NHC(3,5-Me2Pz)}{NP(O)}]2 (9), was isolated as the major product. Finally, the reaction of 5 with PdCl2 resulted in [{NC(OC5H4N)}2{NP(NC(NMe2)2)2}·{PdCl2}] (10). In the latter, the exocyclic P−N bonds are quite robust and are involved in binding to the metal ion. Compounds 6−10 have been characterized by a variety of techniques including X-ray crystallography. In all of the compounds, the bond parameters of the inorganic heterocyclic rings are affected by metalation.
Co-reporter:Vadapalli Chandrasekhar, Mrituanjay D. Pandey, Kandasamy Gopal and Ramachandran Azhakar
Dalton Transactions 2011 vol. 40(Issue 31) pp:7873-7878
Publication Date(Web):04 Jul 2011
DOI:10.1039/C1DT10294J
The reaction of the phosphorus trihydrazide, (S)P[N(Me)-NH2]3 (1) with quinoline-2-carboxaldehyde (C9H6N-2-CHO) in a 1:3 ratio afforded a trishydrazone, (S)P[N(Me)-NCH-2-C9H6N]3 (2). Crystals of 2 were grown in three different solvent media affording an unsolvated (2, monoclinic, P21/n) and two solvated (2·3H2O, trigonal, R3 and 2·2CH3OH, triclinic, P) crystal forms. Each of these, while possessing an essentially similar molecular structure, adopt different crystal packing giving rise to supramolecular structures mediated by a variety of weak interactions: O–H–N, O–H–O, C–H–N, C–H–O, C–H–S, C–H–π, π–π, N–π and S–π. The reaction of 2 with Ag(ClO4)2·6H2O in methanol afforded a dinuclear cationic cage [Ag{(S)P[N(Me)-NCH-2-C9H6N]3}·ClO4]2 (3). The molecular structure of 3 reveals a dimeric structure consisting of two AgI ions that are held together by two ligands. Only two arms of the tris hydrazone ligand are involved in coordination while an unprecedented PS→AgI coordination is seen. This results in the formation of an Ag2S2 dimer that is encapsulated by two trishydrazone ligands. Both compounds 2 and 3 are photoluminescent.
Co-reporter:Vadapalli Chandrasekhar, Tapas Senapati, Atanu Dey and Sakiat Hossain
Dalton Transactions 2011 vol. 40(Issue 20) pp:5394-5418
Publication Date(Web):03 Mar 2011
DOI:10.1039/C0DT01069C
Molecular transition-metal phosphonates are of relatively recent origin and can be assembled by several synthetic strategies. The nuclearity and the structure of the metal aggregates can be modulated by several factors including the stoichiometry of the reactants, nature of the metal precursor and the type of phosphonic acid used. This perspective summarizes some of the recent work carried out on copper(II)-, zinc(II)- and cadmium(II) phosphonates with particular emphasis on their synthesis and structure.
Co-reporter:Vadapalli Chandrasekhar and Puja Singh
Dalton Transactions 2011 vol. 40(Issue 1) pp:114-123
Publication Date(Web):17 Nov 2010
DOI:10.1039/C003339A
The reaction of [n-Bu2SnO]n with 1,5-naphthalenedisulfonic acid tetrahydrate in a 1:1 stoichiometry followed by reaction with 2,2′-bipyridine-N,N′-dioxide (BPDO-I) afforded a 1D-coordination polymer [n-Bu2Sn(BPDO-I)(1,5-C10H6(SO3)2)]n (1) where the disulfonate ligand acts as a bridging ligand between two tin centers. An analogous reaction involving [Ph2SnO]n afforded a trihydrated O,O′-chelated diorganotin cation [{Ph2Sn(BPDO-I)(H2O)3}2+][C10H6(SO3−)2]·2CH3OH (2·2CH3OH). Utilizing two equivalents of BPDO-I in this reaction resulted in the ionic complex [{Ph2Sn(BPDO-I)2(H2O)}2+][C10H6(SO3−)2]·3H2O (3·3H2O). In 2 and 3 the sulfonate ligands are not present in the coordination sphere of tin. Reaction of [n-Bu2SnO]n and 1,5-naphthalenedisulfonic acid tetrahydrate, followed by reaction with [bis(diphenylphosphoryl)methane (DPPOM)] resulted in the formation of, [{n-Bu2Sn(DPPOM)2(H2O)(1,5-C10H6(SO3)(SO3−)}]·H2O (4·H2O). Of the two coordinating groups present in DPPOM, only one PO group is coordinated to the tin atom. The remaining PO motif is free and is involved in intramolecular H-bonding with the tin-bound water molecule. Using [Ph2SnO]n instead of [n-Bu2SnO]n afforded the ionic complex [{Ph2Sn(DPPOM)2}2+{1,5-C10H6(SO3−)2}] (5) where the DPPOM functions as a chelating ligand. The reaction of [n-Bu2SnO]n with 1,5-naphthalenedisulfonic acid tetrahydrate followed by addition of one equivalent of 8-hydroxyquinoline (8-HQ) in presence of triethylamine afforded the neutral dinuclear complex, [(H2O)(8-Q)n-Bu2Sn(μ-1,5-C10H6(SO3)2)n-Bu2Sn(8-Q)(H2O)] (6) where the two tin atoms are bridged by the disulfonate ligand. Compounds 1–6 are thermally stable as shown by their thermogravimetric analyses.
Co-reporter:Vadapalli Chandrasekhar, Tapas Senapati, Atanu Dey, Sakiat Hossain, and Kandasamy Gopal
Crystal Growth & Design 2011 Volume 11(Issue 5) pp:1512-1519
Publication Date(Web):April 11, 2011
DOI:10.1021/cg1014169
The pyridyloxycarbophosphazene, [NC(NMe2)]2[NP(p-OC5H4N)2] (L), reacted with Cd(OAc)2·4H2O to afford a rail-road-like double-strand coordination polymer, [{Cd(CH3COO)2(L)}(CH3OH)(H2O)2]n (1). The crystal structure of 1 reveals that L functions as a bridging ligand to link successive cadmium atoms. Two such parallel-running strands are further interconnected by actetate bridging ligands forming Cd2O2 four-membered connections. The double-stranded coordination polymer is taken into the second dimension by intermolecular hydrogen bonding between the oxygen atoms of the acetate bridge and a tetrameric water cluster. Interaction of L with Cd(NO3)2·4H2O leads to the formation of [Cd(NO3)2(L)(MeOH)]n (2). In the presence of pyridine (Py), this reaction affords [Cd(NO3)2(L)(Py)2]n (3). In contrast to 1, compounds 2 and 3 are single-strand one-dimensional (1-D) coordination polymers. In 1−3, the cadmium atoms are seven-coordinate in a pentagonal−bipyramidal geometry. The reaction of L with ZnCl2, MnCl2, or CoCl2 leads to the formation of [{Zn(Cl)2(L)}(MeOH)]n (4), [Mn(Cl)2(L)2]n (5), and [Co(Cl)2(L)2]n (6). Structure 4 is a simple 1-D coordination polymer containing tetrahedral zinc atoms, while 5 and 6 are macrocycle-linked coordination polymers. In the latter, successive metal atoms are linked by a pair of carbophosphazene ligands to generate 24-membered macrocyclic rings which are interconnected to each other at the metal center to afford the coordination polymer chain.
Co-reporter:V. Chandrasekhar, P. Thilagar, and A. Steiner
Crystal Growth & Design 2011 Volume 11(Issue 5) pp:1446-1449
Publication Date(Web):April 12, 2011
DOI:10.1021/cg2001927
The reaction of [n-BuSn(O)OH]n and 9-hydroxy-9-fluorenecarboxylic acid in the presence of p-X-C6H4-OH (X = F, Br) afforded hydroxyl-rich hexameric organostannoxane prismanes. The crystal structures of these prismanes reveal guest-assisted supramolecular structures. Self-assembly of these compounds on a mica surface affords organooxotin nanotubules.
Co-reporter:Tanima Hajra, Jitendra K. Bera, Vadapalli Chandrasekhar
Inorganica Chimica Acta 2011 Volume 372(Issue 1) pp:53-61
Publication Date(Web):15 June 2011
DOI:10.1016/j.ica.2011.01.021
The reaction of the cyclometalated IrIII dimer [{(ppy)2Ir}2(μ-Cl)2] (ppyH = 2-phenylpyridine) with silver triflate followed by a multidentate ligand [1,4-bis[3-(2-pyridyl)pyrazolylmethyl]benzene (bppb), 1,3,5-tri[3-(2-pyridyl)pyrazolylmethyl]-2,4,6-trimethylbenzene (tppb), 2,4,6-tris(2-pyridyl)-1,3,5-triazine (tptz), 2-chloro-4,6-bis(dipyridin-2-ylamino)-1,3,5-triazine (cddt) or 2,4,6-tris(dipyridin-2-ylamino)-1,3,5-triazine (tdat)] afforded di- or trinuclear compounds: [{Ir(ppy)2}2(μ-bppb)](OTf)2 (1), [{Ir(ppy)2}3(μ-tppb)](OTf)3 (2), [{Ir(ppy)2}2(μ-tptz-OH)](OTf) (3), [{Ir(ppy)2}2(μ-cddt)](OTf)2 (4) and [{Ir(ppy)2}2(μ-tdat)](OTf)2 (5). All of these compounds contain cationic metal cores with corresponding triflate counter anions. The molecular structures of 1–4 reveal that the structural feature of the Ir(ppy)2 center of the starting precursor is conserved in the products. Also, because of the nature of the ligands, there is virtually no electronic communication between the IrIII centers except in 3 where a ring hydroxylation at the triazine carbon atom is effected upon metalation. Compounds 1–5 are robust in solution where they retain their structural integrity. The UV–Vis and emission spectra of 1–5 compounds are very similar to each other with the exception of 3 which seems to possess a different electronic structure. All the compounds are luminescent at room temperature. The emission bands indicate significant contribution from 3LC. Increase in the number of ‘Ir(ppy)2’ units does not have any effect on emission color.Graphical abstractUse of multidentate ligands has afforded a number of multinuclear cyclometalated Ir(III) compounds including a dinuclear compound in which the central triazine ring of the bridging ligand is hydroxylated.Research highlights► Synthesis of multinuclear cyclometalated Ir(III) compounds. ► Nitrogen donor bridging ligands promotes multi-nuclear metal assembly. ► Solution and solid-state structural characterization of multinuclear cyclometalated Ir(III) compounds. ► Photoluminescence behavior of multinuclear cyclometalated Ir(III) compounds.
Co-reporter:Vadapalli Chandrasekhar, Ramakirushnan Suriya Narayanan
Tetrahedron Letters 2011 Volume 52(Issue 27) pp:3527-3531
Publication Date(Web):6 July 2011
DOI:10.1016/j.tetlet.2011.05.006
A new functional organostannoxane cage, SnP, that contains phosphine ligands in its periphery has been structurally utilized as support palladium(0) nanoparticles SnPPd. The latter was shown to catalyze the Heck coupling reactions of wide variety of functionalities efficiently.
Co-reporter:Vadapalli Chandrasekhar, Mrituanjay D. Pandey
Tetrahedron Letters 2011 Volume 52(Issue 16) pp:1938-1941
Publication Date(Web):20 April 2011
DOI:10.1016/j.tetlet.2011.02.051
A novel dipyrene ligand 1 has been designed which shows intramolecular excimer formation in solution. Its specific interaction with Cu2+ or Hg2+ leads to the disruption of the excimer and results in a fluorescence-mediated sensing of these ions in a mixed organic-aqueous solution. Apart from steady-state studies, time-resolved fluorescence measurements also reveal that excimer-switch off caused by metal ion coordination leads to the selective detection of these ions.A novel dipyrene ligand 1 has been designed which shows intramolecular excimer formation in solution. Its specific interaction with Cu2+ or Hg2+ leads to the disruption of the excimer and results in a fluorescence-mediated sensing of these ions in a mixed organic-aqueous solution. Apart from steady-state studies, time-resolved fluorescence measurements also reveal that excimer-switch off caused by metal ion coordination leads to the selective detection of these ions.
Co-reporter:Vadapalli Chandrasekhar, Ramalingam Thirumoorthi, Ramesh K. Metre, Bani Mahanti
Journal of Organometallic Chemistry 2011 696(2) pp: 600-606
Publication Date(Web):
DOI:10.1016/j.jorganchem.2010.09.032
Co-reporter:Vadapalli Chandrasekhar, Bani Mahanti, Priyanka Bandipalli, Kotamarthi Bhanuprakash, Nisanth N. Nair
Journal of Organometallic Chemistry 2011 696(14) pp: 2711-2719
Publication Date(Web):
DOI:10.1016/j.jorganchem.2011.04.011
Co-reporter:Dr. Vadapalli Chrasekhar;Dr. Mrituanjay D. Pey;Seep Kumar Maurya;Dr. Pratik Sen;Dr. Debabrata Goswami
Chemistry – An Asian Journal 2011 Volume 6( Issue 9) pp:2246-2250
Publication Date(Web):
DOI:10.1002/asia.201100032
Co-reporter:Vadapalli Chandrasekhar, Mrituanjay D. Pandey, Biswanath Das, Bani Mahanti, Kandasamy Gopal, Ramachandran Azhakar
Tetrahedron 2011 67(36) pp: 6917-6926
Publication Date(Web):
DOI:10.1016/j.tet.2011.06.073
Co-reporter:Mrituanjay D. Pandey ; Ashutosh Kumar Mishra ; Vadapalli Chandrasekhar ;Sandeep Verma
Inorganic Chemistry 2010 Volume 49(Issue 5) pp:2020-2022
Publication Date(Web):January 29, 2010
DOI:10.1021/ic9022008
This Communication describes a novel adenine−pyrene conjugate (1) and its solid-state structure with silver and copper ions. Single-crystal studies of metal complexes of 1 offer insight into molecular interactions and provide a basis to rationalize possible interactions in the solution state, leading to excimer formation. The robust nature of this interaction was further confirmed by deposition of the silver complex on a graphite surface, which exhibited a remarkable resemblance to its solid-state structure. The structural basis of selective excimer formation in the presence of Ag+ ions presents a viable approach for ratiometric detection of these ions.
Co-reporter:Vadapalli Chandrasekhar ; Ramachandran Azhakar ; Balasubramanian Murugesapandian ; Tapas Senapati ; Prasenjit Bag ; Mrituanjay D. Pandey ; Sandeep Kumar Maurya ;Debabrata Goswami
Inorganic Chemistry 2010 Volume 49(Issue 9) pp:4008-4016
Publication Date(Web):March 19, 2010
DOI:10.1021/ic901531e
A phosphorus-supported multidentate ligand (S)P[N(Me)N═CH-C6H3-2-OH-4-N(CH 2CH3)2]3 (1) has been used to prepare mononuclear complexes LM [M = Fe (2) Co (3)] and trinuclear complexes L2M3 [M = Mn (4), Ni (5), Zn (6), Mg (7), Cd (8)]. In both 2 and 3 the ligand binds the metal ion in a facial coordination mode utilizing three imino nitrogen (3N) and three phenolic oxygen (3O) atoms. The molecular structures of L2Mn3, L2Ni3, L2Zn3, L2Mg3, and L2Cd3 (4−8) are similar; two trihydrazone ligands are involved in coordination to hold the three metal ions in a linear fashion. Each of the trishydrazone ligands behaves as a trianionic hexadentate ligand providing three imino and three phenolic oxygen atoms for coordination to the metal ions. The coordination environment around the two terminal metal ions is similar (3N, 3O) while the central metal ion has a 6O coordination environment. Third-order non-linear optical properties of these compounds as measured by their two-photon absorption (TPA) cross section reveals that while 1 does not possess obvious TPA activity, complexes 2 (3213 GM) and 4 (3516 GM) possess a large TPA cross section at 770 nm.
Co-reporter:Vadapalli Chandrasekhar and Puja Singh
Crystal Growth & Design 2010 Volume 10(Issue 7) pp:3077
Publication Date(Web):June 15, 2010
DOI:10.1021/cg100179q
The reaction of di-n-butyltin oxide with 1,5-naphthalenedisulfonic acid tetrahydrate in a 2:1 ratio afforded [{n-Bu2Sn(μ-OH)}2{μ-1,5-C10H6(SO3)2}]n (1). The latter is a three-dimensional coordination polymer, in a honeycomb architecture, containing [Sn2(μ-OH)2] repeat units that are connected to each other by the bridging coordination action of the disulfonate ligand. Reaction of [n-R2SnO]n (R = n-Bu or Ph) with 1,5-naphthalenedisulfonic acid tetrahydrate in a 1:1 ratio followed by reaction with bifunctional N-oxide ligands (4,4′-bipyridine-N,N′-dioxide (BPDO-II), 1,3-bis(4-pyridyl)propane-N,N′-dioxide (BPDO-III), or P-oxide (1,2-bis(diphenylphosphoryl)ethane (DPPOE)) ligands afforded, depending on the stoichiometry/reaction conditions, various compounds: [{n-Bu2Sn(BPDO-II)2(H2O)2}{1,5-C10H6(SO3)2}] (2); [n-Bu2Sn(μ-BPDO-II)(μ-1,5-C10H6(SO3)2)]n (3); [n-Bu2Sn(μ-DPPOE)(μ-1,5-C10H6(SO3)2)]n (4); [{Ph2Sn(μ-BPDO-II)(H2O)2}{1,5-C10H6(SO3)2}·2H2O]n (5·2H2O); [{n-Bu2Sn(μ-BPDO-III)2}{1,5-C10H6(SO3)2}·5H2O]n (6·5H2O); [{n-Bu2Sn(BPDO-III-H)2}{μ-1,5-C10H6(SO3)2}{1,5-C10H6(SO3)2}]n (7); and [{n-Bu2Sn(DPPOE)2}{μ-1,5-C10H6(SO3)2}2{n-Bu2Sn(CH3OH)(μ-OH)}2·2H2O]n (8·2H2O). On the other hand, the reaction of [n-Bu2SnO]n with 1,5-naphthalenedisulfonic acid tetrahydrate in a 2:1 ratio followed by nicotinic acid N-oxide multifunctional ligand (NO-IV) afforded [(n-Bu2Sn)(μ-1,5-C5H4(NO)(COO))2(μ-1,5-C10H6(SO3)2)(n-Bu2Sn)(H2O)(CH3OH)·CH3OH]n (9·CH3OH) and [(Bu2Sn)(H2O)(μ-1,5-C5H4)(NO)(COO))(μ-1,5-C10H6(SO3)2)1/2]n (10). While 2 is a molecular compound, 3 is a coordination polymer containing both sulfonate and N-oxide bridges. 4 is isostructrual with 3 except that the ligand involved is a bifunctional P-oxide ligand. 5 also is a coordination polymer, although, in this case, only the N-oxide ligands are in the coordination sphere of tin. 6 is a coordination polymer containing interlinked 28-membered macrocycles which are formed as a result of the flexible nature of the BPDO-III ligand. In contrast, in 7 one end of the BPDO-III ligand is protonated and hence does not take any part in coordination to tin. In this case, the coordination polymer is formed by the exclusive coordination action of the disulfonate ligand. Compound 8 reveals it to be a coordination polymer containing alternately [Sn2(μ-OH)2] and a discrete tin unit that are connected by disulfonate ligands. The coordination polymers 9 and 10 are obtained by a variation of crystallization conditions in the three-component reactions using NO-IV as the bridging ligand. While 9 is a neutral porous 2D-coordination polymer consisting of two different types of interconnected diorganotin units, 10 is a nonporous 2D-framework containing only one type of diorganotin unit. Most of the compounds prepared in this study showed good thermal stability, as indicated by their thermogravimetric analyses.
Co-reporter:Vadapalli Chandrasekhar and Ramalingam Thirumoorthi
Dalton Transactions 2010 vol. 39(Issue 10) pp:2684-2691
Publication Date(Web):28 Jan 2010
DOI:10.1039/B922044E
The reaction of 1,1′-ferrocenedicarboxylic acid (LH2) with bis(triphenyltin) oxide afforded a molecular heterobimetallic compound [(Ph3Sn)2L]. In the latter the two carboxylate units of [L]2- are involved in an anisobidentate chelating coordination mode to two triphenyl tin units. The reaction of LH2 with trimethyltin hydroxide or bis(tri-n-butyltin) oxide afforded 2D-coordination polymers [(Me3Sn)2L]n and [(n-Bu3Sn)2L]n which are formed as a result of anisobidentate bridging coordination action of the two carboxylate units of [L]2-. Interestingly the 2D-coordination polymers contain 24-membered macrocycles each of which is comprised of four trialkyl tin units. The coordination unsaturation of [(Ph3Sn)2L] can be utilized to form coordination polymers. Accordingly the reaction of LH2 with bis(triphenyltin) oxide in the presence of ditopic nitrogen ligands such as 4,4′-bipyridine, 4,4′-trimethylenebipyridine or 4,4′-vinylenebipyridine afforded one-dimensional coordination polymers which contain in their backbone three distinct structural components viz., two triorganotin units, a ferrocenyl unit and a bridging nitrogen ligand unit. The coordination polymers, however, do not retain their structural integrity in solution and fall apart to their monomeric units. Electrochemical studies on these hybrid orgaonotin/ferrocene systems reveal that most of them exhibit a single quasi-reversible oxidation peak.
Co-reporter:Vadapalli Chandrasekhar, Palani Sasikumar, Tapas Senapati, Atanu Dey
Inorganica Chimica Acta 2010 Volume 363(Issue 12) pp:2920-2928
Publication Date(Web):15 October 2010
DOI:10.1016/j.ica.2010.03.038
The reaction of Cu(II) or Cd(II) salts with 2,4,6-iPr3C6H2PO3H2, 2,4,6-iPr3C6H2CH2PO3H2 or 2,6-iPr2C6H3OPO3H2 in the presence of strong chelating nitrogen ligands such as 2,2′-bipyridine (bpy), 1,10-phenanthroline (phen), 2-pyridylpyrazole (pypz) or 3,5-dimethyl pyrazole (dmpz) as the ancillary ligands afforded dinuclear copper or cadmium complexes [Cu2(2,4,6-iPr3C6H2PO3H)4(bpy)2] (4), [Cu2(2,6-iPr2C6H3OPO3H)2(bpy)2(OAc)2(CH3OH)2]·(CH3OH) (5), [Cd2(2,6-iPr2C6H3OPO3H)4 (bpy)2(CH3OH)2]·2(CH3OH) (6), [Cd2(2,6-iPr2C6H3OPO3H)4(phen)2] (7), [Cu2(2,6-iPr2C6H3OPO3H)2(PyPz)2(CH3OH)2] (8) and [Cu2(2,4,6-iPr3C6H2CH2PO3H)2(DMPz)2Cl2]·(CH3OH) (9) The molecular structures of 4–7 are grossly similar. The common structural features in these complexes are that the two metal centers are bridged by two bidentate [RPO2(OH)]− ligands generating a central eight-membered ring. Each of the metal centers also contains a chelating nitrogen ligand and a monodentate phosphonate or a phosphate ligand. In 5 and 6 other terminal ancillary ligands are also present. In compound 8, each of the two copper centers contains a monodentate [RPO2(OH)]− ligand along with a molecule of methanol. The two coppers are bridged by two monoanionic pyridylpyrazole ligands. The molecular structure of 9 is similar to that of 4–7. However, in 9 each of the two copper centers contain only terminal monodentate ligands in the form of two chlorides and a pyrazole. Magnetic studies on all of these copper complexes reveal an anti-ferromagnetic behavior at low temperatures. In addition, these complexes were found to be artificial nucleases and can convert supercoiled pBR322 DNA form I into nick form II in 1 min in the presence of an external oxidant through a hydrolytic and/or an oxidative pathway.The reaction of Cu(II) or Cd(II) salts with phosphonic acids (2,4,6-iPr3C6H2PO3H2, 2,6-iPr2C6H3OPO3H2) or phosphate (2,6-iPr2C6H3OPO3H2) in the presence of chelating nitrogen ligands such as 2,2′-bipyridine, 1,10-phenanthroline or 2-pyridylpyrazole as the ancillary ligands afforded dinuclear copper/cadmium phosphonates or phosphates.
Co-reporter:Vadapalli Chandrasekhar;Ramalingam Thirumoorthi
Journal of Chemical Sciences 2010 Volume 122( Issue 5) pp:687-695
Publication Date(Web):2010 September
DOI:10.1007/s12039-010-0057-0
The reaction of SnBr4 with in situ generated 2,4,6-trimethylphenylmagnesium bromide afforded a mixture of (2,4,6-Me3C6H2)2SnBr2 (1) and (2,4,6-Me3C6H2)3SnBr (2) which could be separated from each other by their solubility differences in diethyl ether. On the other hand, the reaction of tin metal with 2,4,6-Me3C6H2CH2Br afforded (2,4,6-Me3C6H2CH2)2SnBr2 (3). Hydrolysis of the latter using triethylamine as the base afforded [{(2,4,6-Me3C6H2CH2)2Sn}2(µ-O)(Br)(µ-OH)]2·2CH2Cl2 (4) while the use of NaOH as the base afforded [{(2,4,6-Me3C6H2CH2)2Sn}2(µ-O)(OH)(µ-OH)]2·2CH2Cl2 (5). Compounds 4 and 5 are dimeric tetraorganodistannoxanes consisting of a central distannoxane (Sn2O2) motif.
Co-reporter:Vadapalli Chandrasekhar, Arun Kumar, Mrituanjay D. Pandey
Journal of Organometallic Chemistry 2010 695(1) pp: 74-81
Publication Date(Web):
DOI:10.1016/j.jorganchem.2009.09.030
Co-reporter:Vadapalli Chandrasekhar and Balasubramanian Murugesapandian
Accounts of Chemical Research 2009 Volume 42(Issue 8) pp:1047
Publication Date(Web):May 19, 2009
DOI:10.1021/ar800221e
Modeled after boron-based scorpionate ligands, acyclic and cyclic phosphorus-containing compounds possessing reactive groups can serve as excellent precursors for the assembly of novel phosphorus-supported ligands that can coordinate multiple sites. In such ligands, the phosphorus atom does not have any role in coordination but is used as a structural support to assemble one or more coordination platforms. In this Account, we describe the utility of inorganic heterocyclic rings such as cyclophosphazenes and carbophosphazenes as well as acyclic phosphorus-containing compounds such as (S)PCl3, RP(O)Cl2, and R2P(O)Cl for building such multisite coordination platforms. We can modulate the number and orientation of such coordination platforms through the choice of the phosphorus-containing precursor. This methodology is quite general and modular and allows the creation of well-defined libraries of multisite coordination ligands. Phosphorus-supported pyrazolyl ligands are quite useful for building multimetallic architectures. Some of these ligands are prone to P−N bond hydrolysis upon metalation, but we have exploited the P−N bond sensitivity to generate hydrolyzed ligands in situ, which are useful to build multimetal assemblies. In addition, the intimate relationship between small molecule cyclophosphazenes and the corresponding pendant cyclophosphazene-containing polymer systems facilitated our design of polymer-supported catalysts for phosphate ester hydrolysis, plasmid DNA modification, and C−C bond formation reactions. Phosphorus hydrazides containing reactive amine groups are ideal precursors for integration into more complex ligand systems. The ligand (S)P[N(Me)N═CH-C6H4-2-OH]3 (LH3) contains six coordination sites, and its coordination response depends upon the oxidation state of the metal ion employed. LH3 reacts with divalent transition metal ions to afford neutral trimetallic derivatives L2M3, where the three metal ions are arranged in a perfectly linear manner in many cases. Incorporating an additional methoxy group into LH3 affords the ligand (S)P[N(Me)N═CH-C6H3-2-OH-3-OMe]3 (L′H3), which contains nine coordination sites: three imino nitrogen atoms, three phenolate oxygen atoms, and three methoxy oxygen atoms. The reaction of L′H3 with transition metal salts in 1:1 ratio leads to the in situ formation of a metalloligand (L′M), which on further treatment with lanthanide salts gives heterobimetallic trinuclear cationic complexes [L′2M2Ln]+ containing a M−Ln−M linear array (M = transition metal ion in a +2 oxidation state). Many of these 3d−4f compounds behave as single-molecule magnets at low temperatures. Although challenges remain in the development of synthetic methods and in the architectural control of the coordination platforms, we see opportunities for further research into coordination platforms supported by main group elements such as phosphorus. As we have shown in this Account, one potential disadvantage, sensitivity of P−N bonds to hydrolysis, can be used successfully to build larger assemblies.
Co-reporter:Vadapalli Chandrasekhar ; Balasubramanian Murugesa Pandian ; Jagadese J. Vittal ;Rodolphe Clérac
Inorganic Chemistry 2009 Volume 48(Issue 3) pp:1148-1157
Publication Date(Web):January 7, 2009
DOI:10.1021/ic801905p
Sequential reaction of LH3 (LH3 = (S)P[N(Me)N═CH−C6H3-2-OH-3-OMe]3) with Co(OAc)2·4H2O followed by reaction with lanthanide salts afforded trinuclear heterobimetalllic compounds {[L2Co2Ln][X]} [Ln = Eu (1), X = Cl; Ln = Tb (2), Dy (3), Ho (4), X = NO3] in excellent yields. These compounds retain their integrity in solution as determined by electrospray ionization mass spectrometry studies. The molecular structures of 1−4 were confirmed by a single-crystal X-ray structural study and reveal that these are isostructural. In all of the compounds, the three metal ions are arranged in a perfectly linear manner and are held together by two trianionic ligands, L3−. The two terminal CoII ions contain a facial coordination environment (3N, 3O) comprising three imino nitrogen atoms and three phenolate oxygen atoms. The coordination geometry about the cobalt atom is severely distorted. An all-oxygen coordination environment (12O) is present around the central lanthanide ion, which is present in a distorted icosahedral geometry. The coordination sphere around the lanthanide ion is achieved by utilizing three phenolate oxygen atoms and three methoxy oxygen atoms of each ligand. In all of these trinuclear complexes (1−4), the Co−Ln distances are around 3.3 Å, while the Co−Co distances range from 6.54 to 6.60 Å. The screw-type coordination mode imposed by the ligand induces chirality in the molecular structure, although all of the complexes crystallize as racemates. Magnetic properties of 1−4 have been studied in detail using dc and ac susceptibility measurements. Dynamic measurements reveal that 2−4 display a single-molecule magnet behavior, while the Co2Eu (1) analogue does not show any out-of-phase ac susceptibility.
Co-reporter:Vadapalli Chandrasekhar and Ramalingam Thirumoorthi
Inorganic Chemistry 2009 Volume 48(Issue 13) pp:6236-6241
Publication Date(Web):May 12, 2009
DOI:10.1021/ic900562n
Reaction of the silanetriol t-BuSi(OH)3 with (p-Me2NC6H4)2TeO in a 4:6 ratio resulted in the formation of [((p-Me2NC6H4)2Te)6(t-BuSiO3)4]·1.5 C7H8 (1·1.5C7H8). In contrast, the reaction of tetrahydroxy-1,3-disiloxane, [t-BuSi(OH)2]2O with (p-MeOC6H4)2TeO in a 3:6 ratio afforded [((p-MeOC6H4)2Te)6(t-BuSi)6O15] · 2 C7H8 (2·2C7H8). 1 possesses a tetrahedron cage structure in which the vertices of the tetrahedron are occupied by silicon atoms. Each pair of silicon atoms is connected to each other by a R2TeO2 motif. The six O−Te−O bridges occupy the edges of the tetrahedron. In contrast to 1, the structure of 2 can be described as a trigonal prismatic cage. The latter consists of two Te3Si3O6 rings that are interconnected to each other through three Si−O−Si linkages. The structure of 2 is reminiscent of a double-six-ring (D6R) secondary building unit (SBU) framework found in zeolites such as faujasite. Reaction of (p-Me2NC6H4)2TeO or (p-MeOC6H4)2TeO with the disiloxane-1,3-diol, [Ph2Si(OH)]2O in a 2:2 ratio afforded [((p-Me2NC6H4)2Te)(OPh2Si−O−SiPh2O)]2 (3) and [((p-MeOC6H4)2Te)(OPh2Si−O−SiPh2O)]2·CH3CN (4·CH3CN). In contrast to 1 and 2, the compounds 3 and 4 contain puckered 12-membered Te2Si4O6 rings.
Co-reporter:Vadapalli Chandrasekhar, Tapas Senapati, E. Carolina Sañudo and R. Clérac
Inorganic Chemistry 2009 Volume 48(Issue 13) pp:6192-6204
Publication Date(Web):June 5, 2009
DOI:10.1021/ic900522u
Reaction of Cu(ClO4)2·6H2O with cyclopentyl phosphonic acid and 2,2′-bipyridine (bpy) in presence of triethylamine afforded a trinuclear compound [Cu3(C5H9PO3)2(bpy)3(MeOH)(H2O)](ClO4)2 (2). The latter dimerizes to a hexanuclear derivative [Cu6(C5H9PO3)4(bpy)6(MeOH)4](ClO4)4 (1) under prolonged reaction conditions. Reaction of CuCl2 with cyclopentyl phosphonic acid and 2,2′-bipyridylamine (bpya) affords a tetranuclear derivative [Cu4(C5H9PO3)2(μ-Cl)2(bpya)4](Cl)2, (MeOH)2 (3). Reaction of the latter with NaClO4 also affords a trinuclear compound [Cu3(C5H9PO3)2(μ-Cl)(bpya)3(H2O)](ClO4) (4). Double and single-bridged hexanuclear species, [{Cu3(C5H9PO3)2(bpy)3(bpp)}(MeOH)2(H2O)(CH2Cl2)(ClO4)2]2 (5), [{Cu3(i-PrPO3)2(bpy)3(4.4′-bpy)(H2O)}(H2O)2(ClO4)2]2 (6), [{Cu3(C5H9PO3)2(bpya)3(4.4′-bpy)(H2O)}(MeOH)(H2O)(ClO4)2]2 (7), and [Cu6(t-BuPO3)4(phen)6(4,4′-bpy)(MeOH)4](CH2Cl2)(H2O)(ClO4)4 (8) (phen = 1,10-phenanthroline) were obtained by the reaction of an in situ generated trinuclear complex with appropriate bridging ligands 4,4′-bipyridine (4,4′-bpy) or 1,3-bis(4-pyridyl)propane (bpp). ESI-MS studies of these complexes reveal that 2−4 retain their structures in solution. Molecular structures of 2−8 were determined by X-ray crystallography. All the compounds reveal a capping coordination mode by tridentate phosphonate [RPO3]2− ligands. Detailed magnetic studies on 2 and 4−8 reveal intramolecular antiferromagnetic interactions between Cu(II) S = 1/2 spins. 2 and 4 are excellent artificial nucleases and can convert supercoiled plasmid DNA (pBR322) into its nicked form without the aid of an external oxidant.
Co-reporter:Vadapalli Chandrasekhar and Ramalingam Thirumoorthi
Inorganic Chemistry 2009 Volume 48(Issue 21) pp:10330-10337
Publication Date(Web):September 29, 2009
DOI:10.1021/ic901479z
The reaction of 1,1,2,3,3-pentamethyltrimethylenephosphinic acid (cycPO2H) with bis(p-methoxyphenyl)tellurium dichloride (1) affords a 12-membered macrocycle [((p-MeOC6H4)2Te)2(μ-O)(μ-cycPO2)(μ4-Cl)]2·C6H6 (2) in good yield. The latter reacts with sodium iodide to give [((p-MeOC6H4)2Te)2(μ-O)(μ-cycPO2)(μ4-I)]2·4C6H6 (3). 2 and 3 are isostructural dicationic macrocycles and contain a Te4P2O6 framework. An interesting aspect of both of these structures is that two counter halide atoms are present as capping ligands above and below the macrocyclic plane enabled by Te---X interactions. In contrast to the macrocyclic product obtained with diorganotellurium dihalide the reaction of diphenyltin dichloride with cycPO2H resulted in the formation of an oxygen-capped cluster [(PhSn)3(μ3-O)(μ-cycPO2)3(μ-OH)3][cycPO2]·CH3CN. The latter is formed by a Sn-Ph cleavage reaction.
Co-reporter:Vadapalli Chandrasekhar and Loganathan Nagarajan
Dalton Transactions 2009 (Issue 34) pp:6712-6714
Publication Date(Web):15 Jul 2009
DOI:10.1039/B905456A
The first example of a hexadecanuclear copper(II) phosphonate containing pyrazole, hydroxide and acetate ancillary ligands has been assembled in a reaction involving copper(II) nitrate, pyrazole, t-butylphosphonic acid and triethylamine.
Co-reporter:Vadapalli Chrasekhar;Tapas Senapati;Rodolphe Clérac
European Journal of Inorganic Chemistry 2009 Volume 2009( Issue 12) pp:1640-1646
Publication Date(Web):
DOI:10.1002/ejic.200900035
Abstract
The reaction of Cu(ClO4)2·6H2O with RPO3H2 (R = cyclopentyl, isopropyl, trichloromethyl) in the presence of chelating nitrogen ligands bpya or bpy afforded dinuclear copper phosphonates [Cu2(μ2-C5H9PO3)2(bpya)2(H2O)2] (H2O)4 (1), [Cu2(μ2-C3H7PO3)2(bpya)2(H2O)2] (H2O)2 (2) and [Cu2(μ2-CCl3PO3)2(bpy)2(MeOH)2] (H2O) (3) [bpya = 2,2′-bipyridylamine, bpy = 2,2′-bipyridine]. The molecular structures of these complexes reveal that they are isostructural and possess two copper centres that are bridged to each other by two isobidentate phosphonate ligands generating an eight-membered Cu2O4P2 ring. Magnetic studies on 2 reveal antiferromagnetic behaviour at low temperatures. Dinuclear complexes 1–3 were found to be excellent nucleases and can convert supercoiled pBR322 DNA form I into nick form II in only 30 min without the need for any external oxidant through a hydrolytic pathway. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
Co-reporter:Vadapalli Chandrasekhar, Mrituanjay D. Pandey, Prasenjit Bag, Siddharth Pandey
Tetrahedron 2009 65(23) pp: 4540-4546
Publication Date(Web):
DOI:10.1016/j.tet.2009.03.098
Co-reporter:Vadapalli Chandrasekhar and Puja Singh
Organometallics 2009 Volume 28(Issue 1) pp:42-44
Publication Date(Web):December 5, 2008
DOI:10.1021/om800972m
The reaction of Ph2SnO with naphthalene-1,5-disulfonic acid tetrahydrate affords, through a Sn−aryl bond cleavage process, the first example of a hydrated monoorganotin cation, [{PhSn(H2O)3(μ-OH)}2][{1,5-C10H6-(SO3)2}2]. The structural elucidation of the latter showed that it contained a tetracationic dinuclear unit where the two tin atoms are bridged by two hydroxide ligands and each tin is hydrated with three molecules of water. Intermolecular hydrogen-bonding interactions between the water molecules and the disulfonate anions result in a pillared three-dimensional network.
Co-reporter:Vadapalli Chandrasekhar and Ramalingam Thirumoorthi
Organometallics 2009 Volume 28(Issue 7) pp:2096-2106
Publication Date(Web):March 3, 2009
DOI:10.1021/om8011739
The reaction of 3,5-pyrazoledicarboxylic acid (LH3) with di- and triorganotin substrates has been investigated. The reaction of LH3 with (PhCH2)2SnCl2 afforded a macrocycle-containing coordination polymer [{((PhCH2)2Sn)6(μ-L)4(μ-OH)2}{((PhCH2)2SnCl)2}]n (1), which upon reaction treatment with pyridine (py) in the presence of water yielded a coordination polymer [{((PhCH2)2Sn)6(μ-L)4(μ-OH)2(py)2}{((PhCH2)2Sn)2(μ-O)(μ-OH)}2]n (2). Treatment of 1 with 2,4,6-collidine in the presence of water afforded [{(PhCH2Sn)12(μ-O)14(μ-OH)6}{((PhCH2)2Sn)6(μ-L)4(μ-OH)2}]·2C4H8O·2C2H5OH·2H2O (3). The latter contains a dodecanuclear oxotin cage as a dication and a hexanuclear tin macrocycle as the dianion. O−H ··· O hydrogen-bonding interaction between the cation and the anion leads to the formation of a supramolecular 2D polymer containing large macrocyclic voids. In a slight variation, if the reaction of LH3 is carried out with Me2SnCl2 in the presence of KOH, a heterobimetallic compound [{(K)2(H2O)2(μ-H2O)3(EtOH)2}{((CH3)2Sn)4(μ-L)3(μ-OH)}]n·2H2O (4) is formed. An interesting aspect of the structure of 4 is that the two potassium atoms present in this compound are bridged to each other by three water molecules. 4 is a 2D-coordination polymer, which is taken into a 3D supramolecular structure by solvent ethanol molecules. The reactions of LH3 with Ph2SnO lead to the formation of an insoluble product 5a, which could be dissolved in hot N,N′-dimethylformamide to afford [{(CH3)2NH2}2{(Ph2Sn)(μ-L)(H2O)}2] (5). An analogue of 5, [{(CH3)2NH2}2{(Ph2Sn)(μ-L)(CH3OH)}2] (6), was also prepared more directly by crystallization of 5a in the presence of dimethylamine or bis(dimethylamino)methane. Both 5 and 6 are dinuclear, and their structural integrity is retained in solution as shown by ESI-MS studies. The reaction of (nBu3Sn)2O with LH3 leads to an unusual Sn−alkyl bond cleavage affording a 2D-coordination polymer [(nBu2Sn)2(μ-L)2(nBu3Sn)2]n (8) where dinuclear tin macrocycles are linked to each other by nBu3Sn bridges. In contrast, the reaction of (Ph3Sn)2O with LH3 affords a dinuclear compound [(Ph3Sn)2(μ-LH)(H2O)]·(H2O)2 (9) where the two tin atoms are coordinated by only the carboxylate oxygen atoms. However, the interaction of the coordinated water molecule along with lattice water leads to the formation of a chair-shaped (H2O)6 cluster, which acts as a bridge between two successive molecules.
Co-reporter:Vadapalli Chandrasekhar and Ramalingam Thirumoorthi
Organometallics 2009 Volume 28(Issue 8) pp:2637-2639
Publication Date(Web):April 2, 2009
DOI:10.1021/om900113q
The first example of a nonanuclear organostiboxane cage, [(Ph2Sb)2(PhSb)7(μ-O)11(μ3-O)3(μ-OH)2(μ-cycPO2)2(cycPO2)2(H2O)2]·2CH3CN·H2O, containing Sb(V) has been assembled by a mild hydrolysis and Sb−C bond cleavage reaction of [(Ph3Sb)2(μ-O)(μ-cycPO2)2] (cycPO2 = 1,1,2,3,3-pentamethyltrimethylene phosphinate).
Co-reporter:Vadapalli Chandrasekhar, Ramakirushnan Suriya Narayanan and Pakkirisamy Thilagar
Organometallics 2009 Volume 28(Issue 20) pp:5883-5888
Publication Date(Web):September 25, 2009
DOI:10.1021/om900487h
A phosphine-rich hexameric organostannoxanne, [n-BuSn(O)COOL]6 (PDrum; L = p-PPh2-C6H4−), has been synthesized by a 6:6 reaction between [n-BuSn(O)OH]n and p-Ph2PC6H4COOH. 119Sn{1H} NMR of PDrum revealed a single resonance at −481.0 ppm, indicating that it possesses the characteristic drum structure that is well-known among organostannoxanes. Reduction of PdCl2 with NaBH4 in the presence of PDrum afforded a palladium nanocomposite, NP-1. HRTEM of NP-1 indicates that the average nanoparticle size is about 3 nm. The latter has been shown to be very effective in mediating Suzuki-coupling reactions involving a number of different substrates. NP-1 can be recycled, and HRTEM analysis of the used catalyst reveals some agglomeration. Treatment of NP-1 with n-hexane and cooling to −25 °C afforded another palladium nanocomposite, NP-2. The latter also is very effective in catalyzing the Suzuki-coupling reaction. HRTEM of NP-2 shows an average nanoparticle size of about 4.3 nm, which remains nearly unchanged even after catalysis. NP-2 is a composite also containing some amounts of SnO2.
Co-reporter:Vadapalli Chandrasekhar, Prasenjit Bag, Mrituanjay D. Pandey
Tetrahedron 2009 65(47) pp: 9876-9883
Publication Date(Web):
DOI:10.1016/j.tet.2009.09.040
Co-reporter:Vadapalli Chandrasekhar, Arun Kumar
Journal of Organometallic Chemistry 2009 694(16) pp: 2628-2635
Publication Date(Web):
DOI:10.1016/j.jorganchem.2009.03.042
Co-reporter:Vadapalli Chandrasekhar, Kandasamy Gopal, Puja Singh, Ramakirushnan Suriya Narayanan and Andrew Duthie
Organometallics 2009 Volume 28(Issue 15) pp:4593-4601
Publication Date(Web):June 25, 2009
DOI:10.1021/om900474a
Organostannoxane drums [n-BuSn(O)O2C-C6H4-4-OR]6 [R = −CH3 (1); −C9H19 (2); −C11H23 (3)] and [n-BuSn(O)O2C-C6H3-3,5-(OR)2]6 [R = −CH3 (4); −C9H19 (5)] were synthesized by the reaction of n-BuSn(O)(OH) with the corresponding carboxylic acid in a 1:1 stoichiometry. Analogous reactions involving [n-Bu2SnO]n in a 1:1 stoichiometry afforded the diorganostannoxane ladders {[n-Bu2SnO2C-C6H4-4-OR]2O}2 [R = −CH3 (6); −C9H19 (7); −C11H23 (8)] and {[n-Bu2SnO2C-C6H3-3,5-(OR)2]2O}2 [R = −CH3 (9) and −C9H19 (10)]. Compounds 1−10 could also be prepared by a solventless methodology, which involved grinding the reactants together in a mortar and pestle at room temperature. Compounds 1−10 exhibit gelation behavior in aromatic solvents. In contrast, in aliphatic solvents gelation behavior was not observed. Among the organostannoxanes reported here, 2, 3, 5, and 8 were found to be extremely efficient gelators based on their critical gelation concentration values. The microstructure of the organometallic gels, investigated by optical and scanning electron microscopy, reveals the presence of cross-linked network structures. The gels formed from 2and 3 can be converted into xerogels by removal of solvent. The latter can be reconverted into the original gels by treatment with aromatic solvents.
Co-reporter:Vadapalli Chandrasekhar, Loganathan Nagarajan, Rodolphe Clérac, Surajit Ghosh, Tapas Senapati and Sandeep Verma
Inorganic Chemistry 2008 Volume 47(Issue 12) pp:5347-5354
Publication Date(Web):May 17, 2008
DOI:10.1021/ic800509f
The reaction of Cu(ClO4)2·6H2O with t-BuP(O)(OH)2 and 3,5-(CF3)2PzH in the presence of triethylamine afforded the dodecanuclear cage {[Et3NH]2[Cu12(μ-3,5-(CF3)2Pz)6(μ3-OH)6(μ-OH)3(μ3-t-BuPO3)2(μ6-t-BuPO3)3][t-BuPO2OH][C6H5CH3]2} (2). The molecular structure of this cage revealed that it possesses a barrel-shaped architechture. The cage structure is built by the cumulative coordination action of phosphonate, hydroxide, and pyrazolyl ligands. A similar reaction involving Cu(NO3)2·3H2O, t-BuP(O)(OH)2, 3,5-dimethylpyrazole, and triethylamine afforded another dodecanuclear cage [Cu12(μ-DMPz)8(η1-DMPzH)2(μ4-O)2(μ3-OH)4(μ3-t-BuPO3)4]·3MeOH (3). The latter is crown-shaped and is built by the coordination of pyrazole, pyrazolyl, phosphonate, hydroxide, oxide, and methanol ligands. Both of the dodecanuclear cages are efficient nucleases in the presence of magnesium monoperoxyphthalate.
Trinuclear Heterobimetallic Ni2Ln complexes [L2Ni2Ln][ClO4] (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, and Er; LH3 = (S)P[N(Me)N═CH−C6H3-2-OH-3-OMe]3): From Simple Paramagnetic Complexes to Single-Molecule Magnet Behavior
Co-reporter:Vadapalli Chandrasekhar ; Balasubramanian Murugesa Pandian ; Ramamoorthy Boomishankar ; Alexander Steiner ; Jagadese J. Vittal ; Ahmad Houri ;Rodolphe Clérac
Inorganic Chemistry 2008 Volume 47(Issue 11) pp:4918-4929
Publication Date(Web):May 7, 2008
DOI:10.1021/ic800199x
The reaction of LH3 with Ni(ClO4)2·6H2O and lanthanide salts in a 2:2:1 ratio in the presence of triethylamine leads to the formation of the trinuclear complexes [L2Ni2Ln][ClO4] (Ln = La (2), Ce (3), Pr (4), Nd (5), Sm (6), Eu (7), Gd (8), Tb (9), Dy (10), Ho (11) and Er (12) and L: (S)P[N(Me)N═CH−C6H3-2-O-3-OMe]3). The cationic portion of these complexes consists of three metal ions that are arranged in a linear manner. The two terminal nickel(II) ions are coordinated by imino and phenolate oxygen atoms (3N, 3O), whereas the central lanthanide ion is bound to the phenolate and methoxy oxygen atoms (12O). The Ni−Ni separations in these complexes range from 6.84 to 6.48 Å. The Ni−Ni, Ni−Ln and Ln−Ophenolate bond distances in 2−12 show a gradual reduction proceeding from 2 to 12 in accordance with lanthanide contraction. Whereas all of the compounds (2−12) are paramagnetic systems, 8 displays a remarkable ST = 11/2 ground state induced by an intramolecular Ni· · ·Gd ferromagnetic interaction, and 10 is a new mixed metal 3d/4f single-molecule magnet generated by the high-spin ground state of the complex and the magnetic anisotropy brought by the dysprosium(III) metal ion.
Co-reporter:Vadapalli Chandrasekhar ; Tapas Senapati ;E. Carolina Sañudo
Inorganic Chemistry 2008 Volume 47(Issue 20) pp:9553-9560
Publication Date(Web):September 10, 2008
DOI:10.1021/ic8011525
The reaction of Cu(ClO4)2·6H2O with cyclopentylphosphonic acid and 1,10-phenanthroline (phen) in the presence of triethylamine afforded a hexanuclear copper(II) complex [Cu6(C5H9PO3)4(1,10-phen)6(MeOH)4](ClO4)4 (1) in over 80% yield. The hexanuclear assembly is held together by the coordination action of four tridentate dianionic [RPO3]2− ligands giving rise to two Cu2P2O4 eight-membered rings in the top and the bottom that are connected to each other by a central Cu2O2 four-membered ring. Every copper atom in 1 is bound by a chelating phenanthroline ligand. Each of the two terminal pairs of copper atoms in the hexanuclear assembly contains methanol molecules of coordination. These labile methanol molecules can be replaced by 1,3-bis(4-pyridyl)propane (bpp) to afford [Cu6(C5H9PO3)4(1,10-phen)6(bpp)2](ClO4)4 (2) where the pincer-like bipyridine ligand acts as a stopper to close both ends of the open hexanuclear cage. Instead, treatment of the in situ generated [Cu6(C5H9PO3)4(2,2′-bpy)6(MeOH)4](ClO4)4 with 4,4′-bipyridine results in the formation of a rail-road-like one-dimensional polymer [{Cu6(C5H9PO3)4(2,2′-bpy)6(4,4′-bpy)2}(ClO4)4]n (3). In addition to structural studies, detailed magnetic studies have been carried out on 1−3 which reveal an S = 1 spin ground-state with low lying excited states.
Co-reporter:Vadapalli Chandrasekhar and Palani Sasikumar
Dalton Transactions 2008 (Issue 45) pp:6475-6480
Publication Date(Web):2008/11/10
DOI:10.1039/B807801G
The X-ray structural characterization of tritylphosphonic acid, Ph3CPO3H2 (1), reveals that it possesses three different structural forms (a hexameric cage, a two-dimensional polymeric sheet and a dimer) depending upon the solvent used for crystallization. The reaction of cerium nitrate with 1 under solvothermal conditions afforded a molecular dinuclear Ce(III) phosphonate, [Ce2{Ph3CPO2(OEt)}4(NO3)2(H2O)4] (2). The molecular structure of 2 reveals that the two cerium atoms are held together by two isobidentate phosphonate and nitrate ligands. The cerium atoms are enveloped by a 8 O coordination environment in a distorted dodecahedral geometry. 2 is found to be a good catalyst for the three-component Biginelli reaction.
Co-reporter:Vadapalli Chandrasekhar, Ramachandran Azhakar, Balasubramanian Murugesa Pandian, Ramamoorthy Boomishankar and Alexander Steiner
Dalton Transactions 2008 (Issue 43) pp:5962-5969
Publication Date(Web):18 Sep 2008
DOI:10.1039/B807074A
The reaction of (S)P[N(Me)NH2]3 with three equivalents of 4(5)-imidazolecarboxaldehyde afforded, in situ, (S)P[N(Me)NCHIm]3 (Im = imidazolyl). The reaction of the latter with metal salts afforded mononuclear complexes [{(S)P[N(Me)NCHIm]3·M}][X]2 [M = Co, X = NO3; M = Ni, X = ClO4; M = Cd, X = NO3]. In these compounds, in the cationic part, the metal ion is bound by three imino and three imidazolyl nitrogen atoms to generate a trigonal prismatic type of coordination environment. Structural analysis of the zinc complex showed the presence of a mononuclear [{(S)P[N(Me)NCHIm]3·Zn}][NO3]2 and a dinuclear 20-membered metallamacrocycle [{(S)P[N(Me)NCHIm]3·Zn}2][NO3]4 in the same unit cell. Solution studies of the zinc complex revealed a monomer–macrocycle equilibrium.
Co-reporter:Vadapalli Chandrasekhar, Palani Sasikumar and Ramamoorthy Boomishankar
Dalton Transactions 2008 (Issue 38) pp:5189-5196
Publication Date(Web):11 Aug 2008
DOI:10.1039/B803256D
The reaction of ArPO3H2 (Ar = 2,4,6-iPr3-C6H2) with Cd(CH3COO)2·2H2O using various co-ligands such as methanol, dimethylformamide (DMF) and 3,5-dimethylpyrazole (DMPZH) resulted in the formation of tetranuclear assemblies [Cd4(ArPO3)2(ArPO3H)4(CH3OH)4]·3(CH3OH) (1), [Cd4(ArPO3)2(ArPO3H)4(DMF)4]·3(DMF) (2) and [Cd4(ArPO3)2(ArPO3H)4(DMF)2(DMPZH)2]·2(DMF)·2(H2O) (3). In all of these compounds the tetranuclear cadmium array, containing two five-coordinate and two six-coordinate cadmium atoms, is held together by two μ4 capping [ArPO3]2− and four anisobidentate μ2 [ArPO2(OH)]− ligands. Each cadmium atom is bound to an additional ancillary ligand. The reaction of ArPO3H2 with Cd(CH3COO)2·2H2O in the presence of the chelating ligand 2,2′-bipyridine (bipy) leads to the exclusive formation of the dinuclear assembly [Cd2(ArPO3H)4(bipy)2]·(CH3OH)(H2O) (4). The latter contains an eight-membered Cd2P2O4 inorganic ring formed as a result of the bridging coordination action of two anisobidentate μ2 [ArPO2(OH)]− ligands. Each cadmium atom is bound by one chelating bipy and one monodentate [ArPO2(OH)]− ligands. Use of four equivalents of 3,5-dimethylpyrazole leads to the formation of the mononuclear derivative [Cd(ArPO3H)2(DMPZH)4] (5). The molecular structure of the latter comprises of a central cadmium atom surrounded by six monodentate ligands. Four of these are neutral pyrazole ligands that occupy the equatorial plane; the remaining two are anionic phosphinate ligands which are present trans to each other. The thermal analysis of 1 and 4 reveals that the char residue obtained at 600 °C consists predominantly of Cd2P2O7.
Co-reporter:Vadapalli Chandrasekhar, Balasubramanian Murugesa Pandian, Ramamoorthy Boomishankar, Alexander Steiner and Rodolphe Clérac
Dalton Transactions 2008 (Issue 38) pp:5143-5145
Publication Date(Web):12 Aug 2008
DOI:10.1039/B804435J
The reaction of (S)P[N(CH3)NCH-C6H3-2-OH-3-OCH3]3 with a MnII salt followed by a LnIII salt (Ln = Eu, Gd and Dy), afforded linear heterometallic complexes [L2Mn2Ln]+ that showed interesting magnetic properties.
Co-reporter:Vadapalli Chandrasekhar, Ramachandran Azhakar, Tapas Senapati, Pakkirisamy Thilagar, Surajit Ghosh, Sandeep Verma, Ramamoorthy Boomishankar, Alexander Steiner and Paul Kögerler
Dalton Transactions 2008 (Issue 9) pp:1150-1160
Publication Date(Web):07 Jan 2008
DOI:10.1039/B712876B
The reaction of cyclohexylphosphonic acid (C6H11PO3H2), anhydrous CuCl2 and 2,2′-bipyridine (bpy) in the presence of triethylamine followed by a metathesis reaction with KNO3 afforded [Cu4(µ-Cl)2(µ3-C6H11PO3)2(bpy)4](NO3)2 (1). In an analogous reaction involving Cu(OAc)2·H2O, the complex [Cu4(µ-CH3COO)2(µ3-C6H11PO3)2(2,2′-bpy)4](CH3COO)2 (2) has been isolated. The three-component reaction involving Cu(NO3)2·3H2O, cyclohexylphosphonic acid and 2,2′-bipyridine in the presence of triethylamine afforded the tetranuclear assembly [Cu4(µ-OH)(µ3-C6H11PO3)2(2,2′-bpy)4 (H2O)2](NO3)3 (3). Replacing 2,2′-bipyridine with 1,10-phenanthroline (phen) in the above reaction resulted in [Cu4(µ-OH)(µ3-C6H11PO3)2(phen)4(H2O)2](NO3)3 (4). In all the copper(II) phosphonates (1–4) the two phosphonate ions bridge the four copper(II) ions in a capping coordination action. Each phosphonate ion bridges four copper(II) ions in a µ4, η3 coordination mode or 4.211 of the Harris notation. Variable-temperature magnetic studies on 1–4 reveal that all four complexes exhibit moderately strong intramolecular antiferromagnetic coupling. The DNA cleavage activity of complexes 1–4 is also described. Compounds 1 and 3 were able to completely convert the supercoiled pBR322 DNA form I to nick form II without any co-oxidant. In contrast, 50% conversion occurred with 2 and 40% with 4. In the presence of magnesium monoperoxyphthalate all four compounds achieved rapid conversion of form I to form II.
Co-reporter:Vadapalli Chrasekhar;Ramachran Azhakar;Balasubramanian Murugesa Pian;Jamie F. Bickley;Alexer Steiner
European Journal of Inorganic Chemistry 2008 Volume 2008( Issue 7) pp:1116-1124
Publication Date(Web):
DOI:10.1002/ejic.200700961
Abstract
The multidentate ligand (S)P[N(Me)N=CHC6H4-o-OH]3 (LH3) reacts with a number of MIII salts to afford the neutral mononuclear complexes LM (M = Sc, Cr, Mn, Fe, Co and Ga). The coordination behaviour of the ligand is hexadentate in all of these complexes, where it encapsulates the metal ion in a facial 3N,3O coordination mode. All the metal complexes have been characterised by spectroscopic and X-ray crystallographic methods. The metal atoms in the complexes LSc, LMn, LFe and LGa adopt a distorted octahedral geometry, whereas the geometries of LCr and LCo are more ideal. The electrochemical behaviour of LMn shows that it can be reversibly reduced (E1/2 = –0.13 V) in a single electron process. The achiral ligand LH3 induces chirality in the metal complexes LM upon coordination with the metal ion. All the complexes crystallise as racemic compounds where both the clockwise (Δ) and anticlockwise (Λ) enantiomorphs are present in the crystal structure in an ordered arrangement. Furthermore, all complexes show supramolecular chiral recognition in their crystal structures; the Δ form recognizes the Λ form by means of intermolecular C–H···O and C–H···S interactions.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Co-reporter:Vadapalli Chrasekhar ;Ramalingam Thirumoorthi
European Journal of Inorganic Chemistry 2008 Volume 2008( Issue 29) pp:4578-4585
Publication Date(Web):
DOI:10.1002/ejic.200800574
Abstract
The reaction of organotin halides R3SnCl (R = Me or benzyl) with ferrocenecarboxylic acid (FcCOOH) in the presence of triethylamine affords Me3SnO2CFc (1) or Bn3SnO2CFc (2) (Bn = benzyl). The latter undergoes a facile ambient temperature double Sn–C bond cleavage to give the monoorganostannoxane, [BnSn(O)O2CFc]6 (3). Compound 3 is also formed by a single Sn–C bond cleavage reaction in the reaction between Bn2SnCl2 and FcCOOH. In contrast, the reaction of Me2SnCl2 with FcCOOH affords Me2Sn(O2CFc)2 (4), where the Sn–C bonds are robust. Organotellurium ferrocene carboxylates [(4-OMe-Ph)2Te(O2CFc)2] (5) and [(4-NMe2-Ph)2Te(O2CFc)2] (6) are obtained in the reaction of the corresponding diorganotellurium oxides/halides with FcCOOH. Whereas 1 is a zig-zag one-dimensional coordination polymer with a square-wave architecture, the structures of 3–6 are molecular. Compound 3 is a hexameric cage and possesses a drum-type structure, whereas 4 is mononuclear and contains a six-coordinate tin with a skewed trapezoidal geometry. In compounds 5 and 6 the lone pairs on tellurium are stereochemically active thereby conferring see-saw geometries. Compounds 1, 2, 4, and 5 show single quasireversible peaks at +0.62, +0.72, +0.66, and +0.64 V, respectively with respect to the Ag/AgCl electrode. Compound 3, which contains six ferrocene arms, shows a single redox event along with a stripping peak. Compound 6 shows quasireversible and irreversible redox events at +0.62 and +1.17 V, respectively. The latter is due to a ligand-centered oxidation.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Co-reporter:Vadapalli Chandrasekhar ;Puja Singh
Organometallics 2008 Volume 27(Issue 16) pp:4083-4087
Publication Date(Web):August 2, 2008
DOI:10.1021/om800359b
The reaction of Me2SnCl2 with 2 equiv of silver nitrate in methanol followed by treatment with 2 equiv of water and 1 equiv of 4,4′-bipyridine in presence of 1,10-phenanthroline afforded the hydrolyzed product [(NO3)(Phen)Me2Sn(μ-OH)SnMe2(Phen)(NO3)]+[NO3]− (4), containing a [R2Sn(μ-OH)SnR2] unit where two diorganotin units are bridged by an unsupported hydroxide ligand.
Co-reporter:Vadapalli Chandrasekhar;Palani Sasikumar;Puja Singh
Journal of Chemical Sciences 2008 Volume 120( Issue 1) pp:105-113
Publication Date(Web):2008 January
DOI:10.1007/s12039-008-0013-4
Organostannoxane cages and aggregates of well-defined composition and structure can be prepared by the reactions of organotin oxides or organotin oxide-hydroxides with protic acids. The utility of this strategy for the preparation of dendrimer-like molecules containing a stannoxane core and a functional periphery is described.
Co-reporter:Vadapalli Chandrasekhar, Kandasamy Gopal and Pakkirisamy Thilagar
Accounts of Chemical Research 2007 Volume 40(Issue 6) pp:420
Publication Date(Web):April 18, 2007
DOI:10.1021/ar600061f
Organooxotin cages, clusters, and coordination polymers containing [Sn2(μ-O)], [Sn2(μ-OH)], [Sn2(μ-O)2], [Sn2(μ-OH)2], and [Sn3(μ3-O)(μ-OR)3] building blocks have been assembled by the reactions of organotin precursors with phosphonic, phosphinic, carboxylic, or sulfonic acids. Various synthetic methodologies including Sn–C bond cleavage reactions and solventless procedures have been utilized to generate several nanodimensional organostannoxane assemblies. The synthesis, structure, and structural interrelationship of these diverse organostannoxane compounds are discussed. The synthetic knowledge gained to prepare specific organostannoxane structural forms in high yields has been utilized for the construction of dendrimer-like molecules. These contain a central stannoxane core and a functional periphery. The functional periphery can be readily modulated to assemble photoactive, electroactive, or multisite coordinating molecules. The synthesis, structure, and potential uses of these compounds are discussed.
Co-reporter:Vadapalli Chandrasekhar
Journal of Inorganic and Organometallic Polymers and Materials 2007 Volume 17( Issue 2) pp:439-446
Publication Date(Web):2007 June
DOI:10.1007/s10904-007-9131-6
Cross-linked polysilanes were prepared by the co-polymerization of Me2SiCl2 or PhMeSiCl2 with varying amounts of divinylbenzene (2–15% by weight) using molten sodium as the dehalogenating agent. All the cross-linked polysilanes were stable to air and could be processed thermally for conversion to silicon carbide. Polymers containing from 5–15% of the cross-linking agent underwent a uniform shrinkage during thermal treatment (1500 °C) to afford β-SiC in good yields. The ceramic was characterized by a variety of techniques including Raman and infrared spectroscopy, powder XRD, as well as Scanning Electron Microscopy (SEM).
Co-reporter:Vadapalli Chandrasekhar, Ramachandran Azhakar, Jamie F. Bickley and Alexander Steiner
Chemical Communications 2005 (Issue 4) pp:459-461
Publication Date(Web):06 Dec 2004
DOI:10.1039/B414353A
A novel linear trinuclear magnesium complex {P(S)[N(CH3)NCHC6H4-o-O]3}2Mg3 was prepared by the reaction of P(S)[N(CH3)NCHC6H4-o-OH]3 with MgCl2·6H2O in the presence of triethylamine. The trinuclear magnesium complex is fluorescent in solution as well as in the solid-state.
Co-reporter:Vadapalli Chandrasekhar and Ramachandran Azhakar
CrystEngComm 2005 vol. 7(Issue 56) pp:346-349
Publication Date(Web):16 May 2005
DOI:10.1039/B504753F
The X-ray crystal structure of {P(S)[N(CH3)NH2]3} reveals a tubular architecture arising out of the N–H⋯SP hydrogen bonds while the corresponding structure of {P(O)[N(CH3)NH2]3} shows a 2-D organization mediated by the N–H⋯OP hydrogen bonds.
Co-reporter:Vadapalli Chandrasekhar, Loganathan Nagarajan, Kandasamy Gopal, Viswanathan Baskar and Paul Kögerler
Dalton Transactions 2005 (Issue 19) pp:3143-3145
Publication Date(Web):22 Aug 2005
DOI:10.1039/B510145J
The synthesis and structure of a novel decanuclear copper(II) cage is reported. The assembly of the cage is facilitated by the cumulative coordinative interaction of tert-butyl phosphonate, 2-pyridylpyrazole and hydroxide ligands with copper(II) ions. Magnetic studies of this decanuclear copper(II) cage indicate complex antiferromagnetic behaviour.
Co-reporter:Vadapalli Chandrasekhar, Selvarajan Nagendran, Kandasamy Gopal, Alexander Steiner and Stefano Zacchini
Chemical Communications 2003 (Issue 7) pp:862-863
Publication Date(Web):10 Mar 2003
DOI:10.1039/B212409B
A 1∶2 reaction of Ph3SnOSnPh31 with RfCOOH 2 leads to the formation of [Ph2Sn(OH)OC(O)(Rf)]23, by means of a facile Sn–C bond cleavage process.
Co-reporter:Vadapalli Chandrasekhar, Venkatasubbaiah Krishnan, Gurusamy Thangavelu Senthil Andavan, Alexander Steiner and Stefano Zacchini
CrystEngComm 2003 vol. 5(Issue 42) pp:245-247
Publication Date(Web):20 Jun 2003
DOI:10.1039/B305694E
Cyclophosphazene hydrazides, N3P3[N(Me)NH2]61 and spiro-N3P3[O2C12H8][N(Me)NH2]42 have been found to organize themselves in supramolecular assemblies in the solid state. Thus, 1 forms a hexagonal close-packed sheet in which each molecule interacts with its six nearest neighbors. All the three ring nitrogen atoms act as proton acceptors while one N(Me)NH2 substituent on each phosphorus atom acts as a proton donor. Compound 2 forms a double chain in which two ring nitrogen atoms act as proton acceptors and one N(Me)NH2 substituent of each phosphorus atom acts as a proton donor. The supramolecular assembly of 1 is further elaborated by intermolecular C–H⋯N interactions.
Co-reporter:Vadapalli Chandrasekhar, Viswanathan Baskar, Savariraj Kingsley, Selvarajan Nagendran and Raymond J. Butcher
CrystEngComm 2001 vol. 3(Issue 17) pp:64-66
Publication Date(Web):
DOI:10.1039/B010108G
The design and solid-state structure of an organoantimony compound containing several weak secondary interactions is described.
Co-reporter:Saurabh Kumar Singh, Thayalan Rajeshkumar, Vadapalli Chandrasekhar, Gopalan Rajaraman
Polyhedron (13 December 2013) Volume 66() pp:81-86
Publication Date(Web):13 December 2013
DOI:10.1016/j.poly.2013.02.037
Series of DFT calculations on [L1Ni(H2O)2Gd(NO3)3] (1) and their transition metal substituted models {CrIIIGdIII}, {FeIIGdIII}, {MnIIGdIII} and {CuIIGdIII} have been performed to probe the electronic effects of the metal substitution on the sign and strength of magnetic coupling. Our results unfold an interesting observation that the strength of the exchange is related to the d-orbital occupancy with occupancy on the eg orbitals resulting in stronger ferromagnetic exchange while progressively filling the t2g orbitals leads to a reduction in the computed J values. Further, we extend our studies to the trinuclear {3d-Ln-3d} [L2M2Ln][ClO4] (LH3 = (S)P[N(Me)N = CH-C6H3-2-OH-3-OMe]3) (here M = Cu2+, Ni2+ and Mn2+ and Ln = GdIII and LaIII) complexes possessing phosphorus, salicylideneaminooxy and Schiff base supported ligands to corroborate our findings in dinuclear models. By computing the nearest neighbor and next-nearest neighbor interactions in all three complexes, our studies reveal that the observation of strong exchange with eg occupancy is preserved also in the trinuclear complexes. This will have implications in the area of molecular coolants where CuII and GdIII are the preferred choice as they inherit no/negligible anisotropy, but our finding suggests that CuII invariably also offers strong exchange interaction – a parameter unsuitable for ideal molecular coolants. Metals ions such as MnII and CrIII are perhaps better choice for molecular refrigeration as they possess large spin values, negligible anisotropy and mediate relatively a weak magnetic exchange interaction.Which 3d metal best suit for molecular coolants in {3d–4f}? Clues from DFT calculations.Download full-size image
Co-reporter:Vadapalli Chandrasekhar ; Gurusamy Thangavelu Senthil Andavan ; Ramachandran Azhakar ;Balasubramanian Murugesa Pandian
Inorganic Chemistry () pp:
Publication Date(Web):February 14, 2008
DOI:10.1021/ic702500n
The cyclophosphazene hydrazide gem-N3P3Ph2[N(Me)NH2]4 was reacted with o-hydroxybenzaldehyde to afford the multisite coordination ligand gem-N3P3Ph2[N(Me)N═CHC6H4-2-OH]4 (LH4). The latter reacted with copper(II) salts to afford a novel tetranuclear copper assembly {N3P3Ph2[N(Me)N═CHC6H4-2-O]4Cu2}2, which contains, remarkably, 15 contiguous inorganic rings.
Co-reporter:Vadapalli Chandrasekhar ; Joydeb Goura ;E. Carolina Sañudo
Inorganic Chemistry () pp:
Publication Date(Web):2017-2-22
DOI:10.1021/ic301060j
The reaction of manganese(II) salts with organophosphonic acid [t-BuPO3H2 or cyclopentyl phosphonic acid (C5H9PO3H2)] in the presence of ancillary nitrogen ligands [1,10-phenanthroline (phen) or 2,6-bis(pyrazol-3-yl)pyridine (dpzpy)], afforded, depending on the stoichiometry of the reactants and the reaction conditions, dinuclear, trinuclear, and tetranuclear compounds, [Mn2(t-BuPO3H)4(phen)2]·2DMF (1), [Mn3(C5H9PO3)2(phen)6](ClO4)2·7CH3OH (2), [Mn3(t-BuPO3)2(dpzpy)3](ClO4)2·H2O (3), [Mn4(t-BuPO3)2(t-BuPO3H)2(phen)6(H2O)2](ClO4)2 (4), and [Mn4(C5H9PO3)2(phen)8(H2O)2](ClO4)4 (5). Magnetic studies on 1, 2, and 4 reveal that the phosphonate bridges mediate weak antiferromagnetic interactions between the MnII ions have also been carried out.
Co-reporter:Vadapalli Chandrasekhar, Palani Sasikumar and Ramamoorthy Boomishankar
Dalton Transactions 2008(Issue 38) pp:NaN5196-5196
Publication Date(Web):2008/08/11
DOI:10.1039/B803256D
The reaction of ArPO3H2 (Ar = 2,4,6-iPr3-C6H2) with Cd(CH3COO)2·2H2O using various co-ligands such as methanol, dimethylformamide (DMF) and 3,5-dimethylpyrazole (DMPZH) resulted in the formation of tetranuclear assemblies [Cd4(ArPO3)2(ArPO3H)4(CH3OH)4]·3(CH3OH) (1), [Cd4(ArPO3)2(ArPO3H)4(DMF)4]·3(DMF) (2) and [Cd4(ArPO3)2(ArPO3H)4(DMF)2(DMPZH)2]·2(DMF)·2(H2O) (3). In all of these compounds the tetranuclear cadmium array, containing two five-coordinate and two six-coordinate cadmium atoms, is held together by two μ4 capping [ArPO3]2− and four anisobidentate μ2 [ArPO2(OH)]− ligands. Each cadmium atom is bound to an additional ancillary ligand. The reaction of ArPO3H2 with Cd(CH3COO)2·2H2O in the presence of the chelating ligand 2,2′-bipyridine (bipy) leads to the exclusive formation of the dinuclear assembly [Cd2(ArPO3H)4(bipy)2]·(CH3OH)(H2O) (4). The latter contains an eight-membered Cd2P2O4 inorganic ring formed as a result of the bridging coordination action of two anisobidentate μ2 [ArPO2(OH)]− ligands. Each cadmium atom is bound by one chelating bipy and one monodentate [ArPO2(OH)]− ligands. Use of four equivalents of 3,5-dimethylpyrazole leads to the formation of the mononuclear derivative [Cd(ArPO3H)2(DMPZH)4] (5). The molecular structure of the latter comprises of a central cadmium atom surrounded by six monodentate ligands. Four of these are neutral pyrazole ligands that occupy the equatorial plane; the remaining two are anionic phosphinate ligands which are present trans to each other. The thermal analysis of 1 and 4 reveals that the char residue obtained at 600 °C consists predominantly of Cd2P2O7.
Co-reporter:Prasenjit Bag, Joydeb Goura, Valeriu Mereacre, Ghenadie Novitchi, Annie. K. Powell and Vadapalli Chandrasekhar
Dalton Transactions 2014 - vol. 43(Issue 43) pp:NaN16376-16376
Publication Date(Web):2014/08/28
DOI:10.1039/C4DT01451K
A new family of tetranuclear heterometallic assemblies, [FeIII2Gd2(H2L)4(η2-NO3)2]·2ClO4·2CH3OH·2H2O (1), [FeIII2Dy2(H2L)4(η2-NO3)2]·2ClO4·2CH3OH·2H2O (2), [FeIII2Tb2(H2L)4(η2-NO3)2]·2ClO4·2CH3OH·2H2O (3), have been synthesized employing a multi-dentate Schiff-base ligand, (E)-2,2′-(2-hydroxy-3-((2-hydroxyphenylimino)methyl)-5-methylbenzylazanediyl)-diethanol (H4L), Fe(ClO4)2·6H2O, and LnIII nitrate salts. These compounds have been structurally characterized by various analytical and spectroscopic techniques. The molecular structures of 1–3 have been confirmed by single crystal X-ray crystallography. All the three complexes contain two FeIII ions at the periphery and two Ln(III) ions in the centre. The entire assembly is held together by four doubly deprotonated [LH2]2− ligands. All the three complexes (1–3) are dicationic in nature and possess an overall Z-type topology. Magnetic measurements reveal the presence of predominant ferromagnetic coupling for all the three compounds at low temperature. The presence of a frequency-dependent out-of-phase signal in the imaginary part of the ac susceptibility plot suggests a slow relaxation of magnetization for 3 (FeIII2Tb2). Furthermore, the magnetization dynamics of all the three complexes have been corroborated by Mössbauer spectroscopy.
Co-reporter:Debabrata Dhara, Debdeep Mandal, Avijit Maiti, Cem B. Yildiz, Pankaj Kalita, Nicolas Chrysochos, Carola Schulzke, Vadapalli Chandrasekhar and Anukul Jana
Dalton Transactions 2016 - vol. 45(Issue 48) pp:NaN19298-19298
Publication Date(Web):2016/11/15
DOI:10.1039/C6DT04321F
NHC-stabilized 2-hydrophosphasilenes are obtained from 1,2-dihydro-2-chlorophosphasilanes as Si(IV) precursors by a NHC-assisted 1,2-elimination of HCl. The NHC-exchange of these compounds is demonstrated as a proof of donor acceptor bonding between NHC and the silicon centre of the “SiP” moiety. We have also explored the possibility of similar exchanges in NHC-stabilized Si2 and P2 compounds. Theoretical DFT calculations were performed to address the nature of Si–P bonding in the NHC-stabilized 2-hydrophosphasilenes.
Co-reporter:Amit Chakraborty, Joydeb Goura, Prasenjit Bag, Arun Kumar Bar, Jean-Pascal Sutter and Vadapalli Chandrasekhar
Dalton Transactions 2016 - vol. 45(Issue 44) pp:NaN17643-17643
Publication Date(Web):2016/09/26
DOI:10.1039/C6DT03144G
Utilizing a new ferrocene-based compartmental ligand, H4L (1), a series of novel heterometallic complexes [{LZn(μ-OAc)Dy}4(μ4-H2O)] (2), [{LZn(μ-OAc)Tb}4(μ4-H2O)] (3), [{LZn(μ-OAc)Ho}4(μ4-H2O)] (4), [L = Fe[(C5H4){–C(Me)N–NC6H3-(o-O)(m-O)}]2] were synthesized and characterized. 2 and 3 crystallize in the monoclinic crystal system in the I2/m space group, whereas 4 crystallizes in the tetragonal crystal system in the I4/m space group. The tetra deprotonated ligand L4− has two distinct coordination compartments: one pocket (2N, 2O) suitable for the transition metal (3d) ions and another pocket (4O) suitable for lanthanide (4f) metal ions. Additionally, the terminal phenoxo group can be utilized for cluster expansion. In all the complexes, the ZnII ion is in a perfect square pyramidal (2N, 3O) geometry whereas the lanthanide ion has a coordination number of eight (8O) in a distorted biaugmented trigonal-prism geometry. The electrochemical properties of 2 and 3 along with ligand H4L (1) were studied by cyclic voltammetry (CV). All the complexes display a similar type of electrochemical behavior viz., one quasi-reversible oxidation typical of a ferrocene/ferrocenium motif. The magnetic properties of all the complexes have also been investigated.
Co-reporter:Debabrata Dhara, Thangavel Vijayakanth, Milan Kr. Barman, Khevath Praveen Kumar Naik, Nicolas Chrysochos, Cem B. Yildiz, Ramamoorthy Boomishankar, Carola Schulzke, Vadapalli Chandrasekhar and Anukul Jana
Chemical Communications 2017 - vol. 53(Issue 61) pp:NaN8595-8595
Publication Date(Web):2017/07/06
DOI:10.1039/C7CC03912C
A facile, straightforward synthesis of N-heterocyclic carbene (NHC)-stabilized 1-hydrosilaimine starting from a silicon(IV)-precursor is reported. It has been employed for the addition of an O–H bond of water under ambient conditions without any additional catalyst.
Co-reporter:Prasenjit Bag, Chandresh Kumar Rastogi, Sourav Biswas, Sri Sivakumar, Valeriu Mereacre and Vadapalli Chandrasekhar
Dalton Transactions 2015 - vol. 44(Issue 9) pp:NaN4340-4340
Publication Date(Web):2015/01/19
DOI:10.1039/C4DT03429E
Four dinuclear lanthanide complexes [Gd2 (H2L)2 (µ-piv)2 (piv)2]·2CHCl3 (1), [Tb2 (H2L)2 (µ-piv)2 (piv)2]·2CHCl3 (2), [Dy2 (H2L)2 (µ-piv)2 (piv)2]·2CHCl3 (3) and [Eu2 (H2L)2 (µ-piv)2 (piv)2]·2CHCl3 (4) were synthesized by the reaction of appropriate Ln(III) chloride salts and a multidentate ligand, 2,2′-(2-hydroxy-3-methoxy-5-methylbenzylazanediyl)diethanol (H3L) in the presence of pivalic acid. 1–4 are neutral and are held by two monoanionic, [H2L]− ligands. The two lanthanide ions are doubly bridged to each other via two phenolate oxygen atoms. Both the lanthanide ions are nine coordinated and possess a distorted capped square antiprism geometry. Photophysical studies reveal that Tb3+ (2) and Dy3+ (3) complexes display strong ligand-sensitized lanthanide-characteristic emission. The Tb3+ complex (2) shows a very high overall quantum yield of 76.2% with a lifetime of 1.752 ms. Magnetic studies reveal single-molecule magnet behavior for 3 which shows in its ac susceptibility studies a two-step slow relaxation yielding two effective relaxation energy barriers of ΔE = 8.96 K and 35.51 K.
Co-reporter:Vadapalli Chandrasekhar, Tapas Senapati, Atanu Dey and Sakiat Hossain
Dalton Transactions 2011 - vol. 40(Issue 20) pp:NaN5418-5418
Publication Date(Web):2011/03/03
DOI:10.1039/C0DT01069C
Molecular transition-metal phosphonates are of relatively recent origin and can be assembled by several synthetic strategies. The nuclearity and the structure of the metal aggregates can be modulated by several factors including the stoichiometry of the reactants, nature of the metal precursor and the type of phosphonic acid used. This perspective summarizes some of the recent work carried out on copper(II)-, zinc(II)- and cadmium(II) phosphonates with particular emphasis on their synthesis and structure.
Co-reporter:Vadapalli Chandrasekhar, Mrituanjay D. Pandey, Kandasamy Gopal and Ramachandran Azhakar
Dalton Transactions 2011 - vol. 40(Issue 31) pp:NaN7878-7878
Publication Date(Web):2011/07/04
DOI:10.1039/C1DT10294J
The reaction of the phosphorus trihydrazide, (S)P[N(Me)-NH2]3 (1) with quinoline-2-carboxaldehyde (C9H6N-2-CHO) in a 1:3 ratio afforded a trishydrazone, (S)P[N(Me)-NCH-2-C9H6N]3 (2). Crystals of 2 were grown in three different solvent media affording an unsolvated (2, monoclinic, P21/n) and two solvated (2·3H2O, trigonal, R3 and 2·2CH3OH, triclinic, P) crystal forms. Each of these, while possessing an essentially similar molecular structure, adopt different crystal packing giving rise to supramolecular structures mediated by a variety of weak interactions: O–H–N, O–H–O, C–H–N, C–H–O, C–H–S, C–H–π, π–π, N–π and S–π. The reaction of 2 with Ag(ClO4)2·6H2O in methanol afforded a dinuclear cationic cage [Ag{(S)P[N(Me)-NCH-2-C9H6N]3}·ClO4]2 (3). The molecular structure of 3 reveals a dimeric structure consisting of two AgI ions that are held together by two ligands. Only two arms of the tris hydrazone ligand are involved in coordination while an unprecedented PS→AgI coordination is seen. This results in the formation of an Ag2S2 dimer that is encapsulated by two trishydrazone ligands. Both compounds 2 and 3 are photoluminescent.
Co-reporter:Vadapalli Chandrasekhar and Palani Sasikumar
Dalton Transactions 2008(Issue 45) pp:NaN6480-6480
Publication Date(Web):2008/11/10
DOI:10.1039/B807801G
The X-ray structural characterization of tritylphosphonic acid, Ph3CPO3H2 (1), reveals that it possesses three different structural forms (a hexameric cage, a two-dimensional polymeric sheet and a dimer) depending upon the solvent used for crystallization. The reaction of cerium nitrate with 1 under solvothermal conditions afforded a molecular dinuclear Ce(III) phosphonate, [Ce2{Ph3CPO2(OEt)}4(NO3)2(H2O)4] (2). The molecular structure of 2 reveals that the two cerium atoms are held together by two isobidentate phosphonate and nitrate ligands. The cerium atoms are enveloped by a 8 O coordination environment in a distorted dodecahedral geometry. 2 is found to be a good catalyst for the three-component Biginelli reaction.
Co-reporter:Vadapalli Chandrasekhar, Balasubramanian Murugesa Pandian, Ramamoorthy Boomishankar, Alexander Steiner and Rodolphe Clérac
Dalton Transactions 2008(Issue 38) pp:NaN5145-5145
Publication Date(Web):2008/08/12
DOI:10.1039/B804435J
The reaction of (S)P[N(CH3)NCH-C6H3-2-OH-3-OCH3]3 with a MnII salt followed by a LnIII salt (Ln = Eu, Gd and Dy), afforded linear heterometallic complexes [L2Mn2Ln]+ that showed interesting magnetic properties.
Co-reporter:Vadapalli Chandrasekhar, Ramachandran Azhakar, Tapas Senapati, Pakkirisamy Thilagar, Surajit Ghosh, Sandeep Verma, Ramamoorthy Boomishankar, Alexander Steiner and Paul Kögerler
Dalton Transactions 2008(Issue 9) pp:NaN1160-1160
Publication Date(Web):2008/01/07
DOI:10.1039/B712876B
The reaction of cyclohexylphosphonic acid (C6H11PO3H2), anhydrous CuCl2 and 2,2′-bipyridine (bpy) in the presence of triethylamine followed by a metathesis reaction with KNO3 afforded [Cu4(µ-Cl)2(µ3-C6H11PO3)2(bpy)4](NO3)2 (1). In an analogous reaction involving Cu(OAc)2·H2O, the complex [Cu4(µ-CH3COO)2(µ3-C6H11PO3)2(2,2′-bpy)4](CH3COO)2 (2) has been isolated. The three-component reaction involving Cu(NO3)2·3H2O, cyclohexylphosphonic acid and 2,2′-bipyridine in the presence of triethylamine afforded the tetranuclear assembly [Cu4(µ-OH)(µ3-C6H11PO3)2(2,2′-bpy)4 (H2O)2](NO3)3 (3). Replacing 2,2′-bipyridine with 1,10-phenanthroline (phen) in the above reaction resulted in [Cu4(µ-OH)(µ3-C6H11PO3)2(phen)4(H2O)2](NO3)3 (4). In all the copper(II) phosphonates (1–4) the two phosphonate ions bridge the four copper(II) ions in a capping coordination action. Each phosphonate ion bridges four copper(II) ions in a µ4, η3 coordination mode or 4.211 of the Harris notation. Variable-temperature magnetic studies on 1–4 reveal that all four complexes exhibit moderately strong intramolecular antiferromagnetic coupling. The DNA cleavage activity of complexes 1–4 is also described. Compounds 1 and 3 were able to completely convert the supercoiled pBR322 DNA form I to nick form II without any co-oxidant. In contrast, 50% conversion occurred with 2 and 40% with 4. In the presence of magnesium monoperoxyphthalate all four compounds achieved rapid conversion of form I to form II.
Co-reporter:Vadapalli Chandrasekhar, Ramachandran Azhakar, Balasubramanian Murugesa Pandian, Ramamoorthy Boomishankar and Alexander Steiner
Dalton Transactions 2008(Issue 43) pp:NaN5969-5969
Publication Date(Web):2008/09/18
DOI:10.1039/B807074A
The reaction of (S)P[N(Me)NH2]3 with three equivalents of 4(5)-imidazolecarboxaldehyde afforded, in situ, (S)P[N(Me)NCHIm]3 (Im = imidazolyl). The reaction of the latter with metal salts afforded mononuclear complexes [{(S)P[N(Me)NCHIm]3·M}][X]2 [M = Co, X = NO3; M = Ni, X = ClO4; M = Cd, X = NO3]. In these compounds, in the cationic part, the metal ion is bound by three imino and three imidazolyl nitrogen atoms to generate a trigonal prismatic type of coordination environment. Structural analysis of the zinc complex showed the presence of a mononuclear [{(S)P[N(Me)NCHIm]3·Zn}][NO3]2 and a dinuclear 20-membered metallamacrocycle [{(S)P[N(Me)NCHIm]3·Zn}2][NO3]4 in the same unit cell. Solution studies of the zinc complex revealed a monomer–macrocycle equilibrium.
Co-reporter:Vadapalli Chandrasekhar and Loganathan Nagarajan
Dalton Transactions 2009(Issue 34) pp:NaN6714-6714
Publication Date(Web):2009/07/15
DOI:10.1039/B905456A
The first example of a hexadecanuclear copper(II) phosphonate containing pyrazole, hydroxide and acetate ancillary ligands has been assembled in a reaction involving copper(II) nitrate, pyrazole, t-butylphosphonic acid and triethylamine.
Co-reporter:Vadapalli Chandrasekhar and Ramalingam Thirumoorthi
Dalton Transactions 2010 - vol. 39(Issue 10) pp:NaN2691-2691
Publication Date(Web):2010/01/28
DOI:10.1039/B922044E
The reaction of 1,1′-ferrocenedicarboxylic acid (LH2) with bis(triphenyltin) oxide afforded a molecular heterobimetallic compound [(Ph3Sn)2L]. In the latter the two carboxylate units of [L]2- are involved in an anisobidentate chelating coordination mode to two triphenyl tin units. The reaction of LH2 with trimethyltin hydroxide or bis(tri-n-butyltin) oxide afforded 2D-coordination polymers [(Me3Sn)2L]n and [(n-Bu3Sn)2L]n which are formed as a result of anisobidentate bridging coordination action of the two carboxylate units of [L]2-. Interestingly the 2D-coordination polymers contain 24-membered macrocycles each of which is comprised of four trialkyl tin units. The coordination unsaturation of [(Ph3Sn)2L] can be utilized to form coordination polymers. Accordingly the reaction of LH2 with bis(triphenyltin) oxide in the presence of ditopic nitrogen ligands such as 4,4′-bipyridine, 4,4′-trimethylenebipyridine or 4,4′-vinylenebipyridine afforded one-dimensional coordination polymers which contain in their backbone three distinct structural components viz., two triorganotin units, a ferrocenyl unit and a bridging nitrogen ligand unit. The coordination polymers, however, do not retain their structural integrity in solution and fall apart to their monomeric units. Electrochemical studies on these hybrid orgaonotin/ferrocene systems reveal that most of them exhibit a single quasi-reversible oxidation peak.
Co-reporter:Vadapalli Chandrasekhar and Puja Singh
Dalton Transactions 2011 - vol. 40(Issue 1) pp:NaN123-123
Publication Date(Web):2010/11/17
DOI:10.1039/C003339A
The reaction of [n-Bu2SnO]n with 1,5-naphthalenedisulfonic acid tetrahydrate in a 1:1 stoichiometry followed by reaction with 2,2′-bipyridine-N,N′-dioxide (BPDO-I) afforded a 1D-coordination polymer [n-Bu2Sn(BPDO-I)(1,5-C10H6(SO3)2)]n (1) where the disulfonate ligand acts as a bridging ligand between two tin centers. An analogous reaction involving [Ph2SnO]n afforded a trihydrated O,O′-chelated diorganotin cation [{Ph2Sn(BPDO-I)(H2O)3}2+][C10H6(SO3−)2]·2CH3OH (2·2CH3OH). Utilizing two equivalents of BPDO-I in this reaction resulted in the ionic complex [{Ph2Sn(BPDO-I)2(H2O)}2+][C10H6(SO3−)2]·3H2O (3·3H2O). In 2 and 3 the sulfonate ligands are not present in the coordination sphere of tin. Reaction of [n-Bu2SnO]n and 1,5-naphthalenedisulfonic acid tetrahydrate, followed by reaction with [bis(diphenylphosphoryl)methane (DPPOM)] resulted in the formation of, [{n-Bu2Sn(DPPOM)2(H2O)(1,5-C10H6(SO3)(SO3−)}]·H2O (4·H2O). Of the two coordinating groups present in DPPOM, only one PO group is coordinated to the tin atom. The remaining PO motif is free and is involved in intramolecular H-bonding with the tin-bound water molecule. Using [Ph2SnO]n instead of [n-Bu2SnO]n afforded the ionic complex [{Ph2Sn(DPPOM)2}2+{1,5-C10H6(SO3−)2}] (5) where the DPPOM functions as a chelating ligand. The reaction of [n-Bu2SnO]n with 1,5-naphthalenedisulfonic acid tetrahydrate followed by addition of one equivalent of 8-hydroxyquinoline (8-HQ) in presence of triethylamine afforded the neutral dinuclear complex, [(H2O)(8-Q)n-Bu2Sn(μ-1,5-C10H6(SO3)2)n-Bu2Sn(8-Q)(H2O)] (6) where the two tin atoms are bridged by the disulfonate ligand. Compounds 1–6 are thermally stable as shown by their thermogravimetric analyses.
Co-reporter:Vadapalli Chandrasekhar and Ramesh K. Metre
Dalton Transactions 2012 - vol. 41(Issue 38) pp:NaN11691-11691
Publication Date(Web):2012/07/16
DOI:10.1039/C2DT31153D
The reaction of ferrocenedicarboxylic acid with triphenylbismuth in a 1:1 ratio under solvothermal conditions afforded the 1D coordination polymer [Bi2(μ2-η2-OOCFcCOO-μ2-η2)(η2-OOCFcCOO-η2)(μ2-η2-OOCFcCOO-η2)]n (1). In this polymer two types of bismuth centers (hepta- and octacoordinate) are present and are interconnected by the bridging coordination of ferrocene dicarboxylate ligands. The reaction of ferrocenecarboxylic acid with triphenylbismuth in a 1:3 ratio, in toluene, under refluxing conditions, afforded the 1D coordination polymer [Bi(μ2-η2-FcCOO)(η2-FcCOO)2]n (2). In the solid state, 2 exists as a helical polymer, where the inner bismuth chain is enclosed by an external sheath of ferrocene carboxylate ligands. In solution, however, 2 decomposes into the monomeric repeat unit [Bi(FcCOO)3] which is indicated by ESI-MS as well as cyclic voltammetric studies. Thus, a single, quasi-reversible redox event is seen for 2 in solution. The reaction of triphenylbismuth with ferrocenecarboxylic acid in a 1:1 stoichiometry afforded the molecular dimer [Bi2(μ2-η2-FcCOO)2(η2-FcCOO)4(H2O)4]·(2FcCOOH) (3). Compounds 1–3 reveal rich supramolecular architectures in the solid state as a result of the presence of C–H⋯O, C–H⋯π and π⋯π interactions.
Co-reporter:Vadapalli Chandrasekhar, Prasenjit Bag, Balasubramanian Murugesapandian and Mrituanjay D. Pandey
Dalton Transactions 2013 - vol. 42(Issue 43) pp:NaN15456-15456
Publication Date(Web):2013/08/12
DOI:10.1039/C3DT51431E
The sequential reaction of a phosphorus-based trishydrazone ligand, LH3 with anhydrous ZnCl2 and LnCl3·6H2O in a 2:2:1 stoichiometric ratio in the presence of triethylamine as the base leads to the formation of monocationic trinuclear complexes [L2Zn2Ln]Cl {Ln = Gd (1), Tb (2), Nd (3), Eu (4) and L = [(S)P[N(Me)NCH–C6H3-2-O-3-OMe]3}. All the three metal ions, in each of these compounds, are arranged in a linear fashion. The two terminal Zn(II) ions are encapsulated by three imino and three phenolate oxygen atoms while the lanthanide ion remains in the centre with an all-oxygen coordination environment. Detailed photophysical measurements reveal the complete absence of antenna sensitization in all the four complexes. However, a strong emission was found for 2 and 4 when excited directly at their f–f levels.
Co-reporter:Vadapalli Chandrasekhar, Dipankar Sahoo, Ramakirushnan Suriya Narayanan, Raymond J. Butcher, Franscesc Lloret and Emilio Pardo
Dalton Transactions 2013 - vol. 42(Issue 23) pp:NaN8196-8196
Publication Date(Web):2013/04/25
DOI:10.1039/C3DT00103B
Structure and characterization of [Cu26{2,3,5,6-(Me)4C6H-CH2-PO3}18(μ2-OH)4(μ3-OH)6(μ4-Cl)6(μ-OH2)2(OH2)2(MeCN)4]·6MeCN·15H2O (1) is reported. Complex 1 is the largest discrete molecular homometallic transition metal phosphonate assembly. Remarkably, this gigantic molecular phosphonate has been prepared at room temperature using a normal solution synthetic method.
Co-reporter:Vadapalli Chandrasekhar and Ramakirushnan Suriya Narayanan
Dalton Transactions 2013 - vol. 42(Issue 18) pp:NaN6632-6632
Publication Date(Web):2013/02/15
DOI:10.1039/C3DT33084B
Pyridyloxy cyclophosphazenes, spiro-N3P3(O2C12H8)(O-C5H4N-3)4 (L1), dispiro-N3P3(O2C12H8)2(O-C5H4N-3)2 (L2) and dispiro-N3P3(O2C12H8)2(O-C5H4N-4)2 (L3) were prepared and characterized. The crystal structure of L1 was determined which showed that the cyclophosphazene ring is planar. The reaction of L1 with anhydrous copper(II) chloride or silver nitrate afforded L2M4 metallamacrocycles [{L1}2{ClCu(μ-Cl)2CuCl}]2·8CHCl3 (3) and [{L1}2{(DMF)0.5(NO3)0.5Ag}2{Ag(μ2-(O)NO2)(H2O)}2]{μ-[NO3]}·CH3OH (4) respectively. The molecular structure of 3 reveals that two CuCl2 dimers are bridged to each other in a complex metallamacrocycle that involves four metal ions and two ligands. The molecular structure of 4 is similar to that of 3 except for the presence of weak argentophilic interactions between the two Ag(I) centers. Also, a nitrate anion, which is trapped in the centre of the tetrameric assembly, assists in holding two Ag(I) ions together and 4 serves as a single source precursor for silver nanoparticles. The reaction L1 with ZnCl2 and Cd(NO3)2·4H2O afforded the 1D-coordination polymers [{L1}{ZnCl2}2]n·2nCH3OH·2nH2O (5) and [{L1}2{Cd(CH3OH)2(NO3)2}2{Cd(NO3)2(H2O)}]n·3nCH3OH·3nH2O (6) respectively. While in 5 the 20-membered macrocycles are inter-connected directly, in 6 they are bridged by a Cd(II) connector. The reaction of L2 with CoCl2 afforded the 1D-coordination polymer [{L2}2{CoCl2}]n·2nCHCl3 (7) which also contains interconnected 20-membered metallamacrocycles. On the other hand, the reaction of L2 with CuCl2 afforded [{L2}2{ClCu(μ-Cl)}2]n·2nCHCl3·nH2O (8) which is a 1D-coordination polymer that contains {ClCu(μ-Cl)2CuCl} units. The reaction of L3 with CuCl2 and Cd(NO3)2·4H2O afforded [{L3}2{CuCl2}]n·nDMF (9) and [{L3}2{Cd(NO3)2}]n·nCHCl3·nCH2Cl2·nH2O (10) respectively. While 9 is a 2D-coordination polymer containing 48-membered metallamacrocycles, 10 is a 1D-coordination polymer containing interconnected 24-membered metallamacrocycles which possess spirocyclic cadmium ions as nodes.
Co-reporter:Dipankar Sahoo, Ramakirushnan Suriyanarayanan and Vadapalli Chandrasekhar
Dalton Transactions 2014 - vol. 43(Issue 28) pp:NaN10909-10909
Publication Date(Web):2014/05/16
DOI:10.1039/C4DT00720D
The reaction of vanadium(III) trichloride with tert-butylphosphonic acid (t-BuPO3H2) in the presence of 1,10-phenanthroline/2,2′-bipyridine as an ancillary ligand in acetonitrile at room temperature afforded two dinuclear dicationic vanadium(IV) complexes [(VO)2(phen)2{t-BuPO2(OH)}2(OH2)2]·2Cl [1] and [(VO)2(bipy)2{t-BuPO2(OH)}2(OH2)2]·2Cl [2]. On the other hand, when the reaction was carried out in methanol, the dinuclear vanadium(V) complex [(VO)2(bipy)2(μ2-O)2(t-BuPO3)2]·2CH3OH·0.5CH2Cl2 [3] was isolated. While 1 and 2 contain two six-membered V2P2O4 rings, 3 contains a unique four-membered V2O2 ring. Replacement of tert-butylphosphonic acid by tritylphosphonic acid (Ph3CPO3H2) under the same reaction conditions in methanol leads to the formation of dicationic trinuclear vanadium(IV) complexes [(VO)3(phen)3(Ph3CPO3)2(OH2)3]·CHCl3·2(OH)·2MeOH·1.5H2O [4] and [(VO)3(bipy)3(Ph3CPO3)2(CH3OH)3]·2(OH)·4CH3OH·5H2O [5]. In these complexes, the triangular V(IV) platform is held together by two bicapping tripodal phosphonate ligands. Replacement of the chelating 2,2′-bipyridine ligand with 3,5-dimethyl-1H-pyrazole, under the same reaction conditions, afforded a tetranuclear vanadium(V) complex [{(VO)4(Ph3CPO3Me)4(μ-O)4}Cl]{3,5-Me2PzH2}·3C7H8·H2O·CH3OH [6]. Remarkably 6 possesses a unique bowl-shaped structure encapsulating a chloride anion.
Co-reporter:Amit Chakraborty, Prasenjit Bag, Eric Rivière, Talal Mallah and Vadapalli Chandrasekhar
Dalton Transactions 2014 - vol. 43(Issue 23) pp:NaN8932-8932
Publication Date(Web):2014/04/15
DOI:10.1039/C4DT00209A
A family of dinuclear 3d–4f heterobimetallic complexes [LNi(H2O)(μ-OAc)Ln(NO3)2]·CH3CN; {Ln = DyIII (1), TbIII (2), HoIII (3), GdIII (4), ErIII (5), YIII (6)} have been synthesized by utilizing a ferrocene-based, dual compartmental ligand H2L. 1–6 are isostructural and crystallize in the triclinic (P) space group. In these complexes NiII is present in the inner coordination sphere of the dianionic [L]2− ligand; LnIII is encapsulated in the outer coordination pocket. NiII shows a 2N, 4O coordination environment in a distorted octahedral geometry, while the LnIII ion possesses a 9O coordination environment in a distorted tricapped trigonal prismatic geometry. ESI-MS studies suggest that the structural integrity of 1–6 is retained in solution. Electrochemical studies reveal that these complexes show a reversible one-electron response typical of the ferrocene motif along with an irreversible one-electron oxidation involving the NiII/NiIII couple. Magnetic studies revealed the presence of ferromagnetic exchange coupling between NiII and LnIII centers as shown by the increase of χMT value upon cooling below 50 K for compounds 1, 2, 4 and 5. Further, dynamic magnetic susceptibility measurements (1–3) confirm the absence of an out-of-phase (χ′′) signal at zero dc fields. However, when these measurements were carried out at 1000 Oe dc field the χ′′ signal was observed, although maxima could not be detected up to 2 K.
Co-reporter:Dipankar Sahoo, Ramakirushnan Suriyanarayanan, Ramesh K. Metre and Vadapalli Chandrasekhar
Dalton Transactions 2014 - vol. 43(Issue 19) pp:NaN7313-7313
Publication Date(Web):2014/03/04
DOI:10.1039/C3DT53614A
The reaction of zinc(II) perchlorate with trichloromethyl phosphonic acid at room temperature afforded, upon crystallization, a two-dimensional layered coordination polymer possessing a dinuclear repeat unit, [{Zn2(Cl3CPO3)2(H2O)3}·1.5H2O]n (1). Modification of the above reaction by involving a co-ligand afforded the tetranuclear complex, [{Zn4(η1-DMPzH)6(Cl3C–PO3)2}(μ-OH)2(ClO4)2] (2). The molecular structure of 2 reveals that the tetranuclear core is non-planar and consists of three contiguous inorganic rings which include one 8-membered Zn2P2O4 ring and two six-membered Zn2PO3 rings. Replacement of Zn(ClO4)2·6H2O with ZnCl2 under the same reaction conditions that afforded 2 allowed the formation of the dinuclear complex [{(ZnCl)2(η2-Pz)2(Cl3CPO3)}(Et3NH)2] (3). 3 possesses a bicyclic core containing a seven-membered Zn2N2O2P ring. In 3, the phosphoryl oxygen atom (PO) is involved in a bifurcated hydrogen bonding interaction with the triethylammonium cation. The reaction of ZnCl2 and 2,3,5,6-(Me)4C6HCH2PO3H2 afforded the octanuclear complex [Zn8(Cl)6{2,3,5,6-(Me)4C6HCH2PO3}6(Et3N)2](Et3NH)2]·2n-hexane·3H2O (4). The core of 4 is ellipsoid-shaped with the end–end polar distance (C–C) being ∼20 Å.
Co-reporter:Ramesh K. Metre, Chandrajeet Mohapatra, Dipankar Sahoo and Vadapalli Chandrasekhar
Dalton Transactions 2014 - vol. 43(Issue 8) pp:NaN3371-3371
Publication Date(Web):2013/12/04
DOI:10.1039/C3DT53050G
The reactions of RSnCl3 [R = 2-(phenylazo)phenyl] with phosphonic acids, RPO3H2 (R = t-Bu, C6H11) or (ArO)2PO2H (Ar = 4-NO2-C6H5O) in refluxing THF afforded hexatin cages, [(RSn)6(μ-OH)6(μ3-O)2(t-BuPO3)4]·5THF (1), [(RSn)6(μ-OH)6(μ3-O)2(C6H11PO3)4]·THF (2) and [(RSn)6(μ-OH)4(μ3-O)2{(NO2C6H4O)PO3}4]·THF (3), respectively. On the other hand, the reactions of RSnCl3 with 1,1,2,3,3-pentamethylene phosphinic acid [cycPO2H] or Ph2P(O)OH under similar reaction conditions afforded trinuclear O-capped clusters [(RSn)3(μ3-O) (μ2-OH)3 (μ-cycPO2)3] [cycPO2]·CH3CN·H2O (4) and [(RSn)3(μ3-O) (μ2-OH)3 (μ-Ph2PO2)3] [Ph2PO2]·CH3CN·CH2Cl2 (5) respectively. Molecular structures of 1–3 reveal that the intramolecular N→Sn coordination found in RSnCl3 is hemilabile; 1–3 do not contain such a feature and the tin atoms in these compounds are six coordinate, possessing a 1C, 5O coordination environment in a distorted octahedral geometry. The cage structures in 1–3, containing two trinuclear sub-units, are formed as a result of the coordination action of several ligands: 4 μ3-(η1η1η1)[RPO3]2−, 2 μ3-O2− and 6 μ-OH. The molecular structures of 4–5 reveal them to be cationic trinuclear complexes where 3 tin and 4 oxygen atoms occupy the vertices of a distorted cube while one of the vertices is unoccupied. The molecular structures of 4–5 also reveal that the intramolecular N→Sn coordination present in RSnCl3 is absent in these compounds attesting to the hemilabile nature of this interaction.
Co-reporter:Sourav Biswas, Sourav Das, Jan van Leusen, Paul Kögerler and Vadapalli Chandrasekhar
Dalton Transactions 2015 - vol. 44(Issue 44) pp:NaN19293-19293
Publication Date(Web):2015/10/07
DOI:10.1039/C5DT03060A
The reaction of LnCl3·6H2O (Ln = Dy3+, Tb3+ and Ho3+) with the multisite coordinating ligand N′-(2-hydroxy-3-(hydroxymethyl)-5-methylbenzylidene)acetohydrazide (LH3) in the presence of pivalic acid (PivH) leads to the formation of three isostructural homometallic pentanuclear complexes, [Dy5(LH)4(η1-Piv)(η2-Piv)3(μ2–η2η1Piv)2(H2O)]·Cl·9·5H2O·5MeOH (1), [Tb5(LH)4(η1-Piv)(η2-Piv)3(μ2–η2η1Piv)2(H2O)]·Cl·10.5H2O·2MeOH·2CHCl3 (2) and [Ho5(LH)4(η1-Piv)(η2-Piv)3(μ2–η2η1Piv)2(H2O)]·Cl·14.5H2O·2CHCl3 (3). 1–3 are monocationic and are comprised of four doubly deprotonated [LH]2− ligands along with six pivalate ions. These complexes possess a [2.2] spirocyclic topology formed by the fusion of two triangles of LnIII ions at a common vertex. The magneto chemical analysis reveals the presence of antiferromagnetic exchange interactions at low temperature, and the DyIII complex 1 gives an out-of-phase signal with a small curvature in alternating current (ac) magnetic susceptibility measurement. Application of a 3000 G static field during ac measurement intensifies the signals, revealing a second slow relaxation process in the DyIII analogue.
Co-reporter:Sakiat Hossain, Sourav Das, Amit Chakraborty, Francesc Lloret, Joan Cano, Emilio Pardo and Vadapalli Chandrasekhar
Dalton Transactions 2014 - vol. 43(Issue 26) pp:NaN10174-10174
Publication Date(Web):2014/04/11
DOI:10.1039/C4DT00465E
The reaction of 8-quinolinol-2-carboaldoxime (LH2) with NiII and LnIII salts afforded the heterometallic decanuclear compounds [Ni8Dy2(μ3-OH)2(L)8(LH)2(H2O)6](ClO4)2·16H2O (1), [Ni8Gd2(μ3-OH)2(L)8(LH)2(H2O)4(MeOH)2](NO3)2·12H2O (2), [Ni8Ho2(μ3-OH)2(L)8(LH)2(H2O)4(MeOH)2](ClO4)2·2MeOH·12H2O (3) and [Ni8Tb2 (μ3-OH)2(L)8(LH)2(MeOH)4(OMe)2]·2CH2Cl2·8H2O (4). While compounds 1–3 are dicationic, compound 4 is neutral. These compounds possess an S-shaped architecture and comprise a long chain of metal ions bound to each other. In all the complexes, the eight NiII and two LnIII ions of the multimetallic ensemble are hold together by two μ3-OH, eight dianionic (L2−) and two monoanionic oxime ligands (LH−) whereas compound 4 has two μ3-OH, eight dianionic (L2−), two monoanionic oxime ligands (LH−) and two terminal methoxy (MeO−) ligands. The central portion of the S-shaped molecular wire is made up of an octanuclear NiII ensemble which has at its two ends the LnIII caps. Magnetic studies on 1–4 reveal that the magnetic interactions between neighboring metal ions are negligible at room temperature. On the other hand, at lower temperatures in all the compounds anti-ferromagnetic interactions seem to be dominated. Analysis of the magnetic data for the GdIII derivative indicates NiII–NiII anti-ferromagnetic interactions and GdIII–NiII ferromagnetic interactions at low temperatures. A theoretical density functional study on the magnetic behavior of the GdIII derivative suggests that while the weak ferromagnetic interaction between GdIII and NiII is in line with the expectation of the magnetic interactions between orthogonal d and f orbitals, antiferromagnetic NiII–NiII interactions are related to the wide Ni–O–Ni angles (∼102°) and quasi-planar conformation of the Ni2O2 core.
Co-reporter:Joydeb Goura, James P. S. Walsh, Floriana Tuna and Vadapalli Chandrasekhar
Dalton Transactions 2015 - vol. 44(Issue 3) pp:NaN1149-1149
Publication Date(Web):2014/11/05
DOI:10.1039/C4DT01603C
The reaction of the hydrazone, 2-methoxy-6-(pyridin-2-yl-hydrazonomethyl) phenol (LH) with lanthanide(III) nitrate salts in the presence of excess triethylamine afforded the heptanuclear Ln(III) complexes: [Gd7(L)6(μ3-OH)8(NO3)4(H2O)]·(NO3)3·8CH3CN·H2O (1), [Tb7(L)6(μ3-OH)8(NO3)4]·(NO3)3·9CH3CN·2CH3OH·3H2O (2), [Dy7(L)6(μ3-OH)8(NO3)4(H2O)]·(NO3)3·7CH3CN·3H2O (3), [Ho7(L)6(μ3-OH)8(NO3)4]·(NO3)3·11CH3CN·2CH3OH·2H2O (4) and [Er7(L)6(μ3-OH)8(NO3)4]·(NO3)3·8CH3CN·2CH3OH (5). Single crystal X-ray diffraction studies reveal that these complexes are tri-cationic, possessing three nitrate counter anions. The heptanuclear ensemble is non-planar and consists of six [L]− and eight μ3-OH ligands. These compounds show an interesting structural motif with two incomplete cubes fused to each other through a common Ln(III) ion. Compound 1 exhibits a magnetocaloric effect, with (−ΔSm(T) = 27.7 J kg−1 K−1 at 3 K and under a field change of 0–7 T), while compound 3 shows slow magnetic relaxation at very low temperatures.
Co-reporter:Joydeb Goura, Jamie Brambleby, Craig V. Topping, Paul A. Goddard, Ramakirushnan Suriya Narayanan, Arun Kumar Bar and Vadapalli Chandrasekhar
Dalton Transactions 2016 - vol. 45(Issue 22) pp:NaN9249-9249
Publication Date(Web):2016/04/27
DOI:10.1039/C5DT03871E
Through the use of a multi-site compartmental ligand, 2-methoxy-6-[{2-(2-hydroxyethylamino)ethylimino}methyl]phenol (LH3), the family of heterometallic, trinuclear complexes of the formula [CoIII2Ln(L)2(μ-O2CCH3)2(H2O)3]·NO3·xMeOH·yH2O has been expanded beyond Ln = DyIII to include GdIII (1), TbIII (2), HoIII (3) and ErIII (4) for 1, 3 and 4 (x = 1; y = 1) and for 2 (x = 0; y = 2). The metallic core of these complexes consists of a (CoIII–LnIII–CoIII) motif bridged in a bent geometry resulting in six-coordinated distorted CoIII octahedra and nine-coordinated LnIII monocapped square-antiprisms. The magnetic characterization of these compounds reveals the erbium and terbium analogues to display a field induced single-ion magnetic behavior similar to the dysprosium analogue but at lower temperatures. The energy barrier for the reversal of the magnetization of the CoIII2TbIII analogue is Ueff ≥ 15.6(4) K, while for the CoIII2ErIII analogue Ueff ≥ 9.9(8) K. The magnetic properties are discussed in terms of distortions of the 4f electron cloud.
Co-reporter:Ramakirushnan Suriya Narayanan and Vadapalli Chandrasekhar
Dalton Transactions 2016 - vol. 45(Issue 5) pp:NaN2283-2283
Publication Date(Web):2015/11/27
DOI:10.1039/C5DT03537F
The coordination behaviour of hexakis(3-pyridyloxy)cyclophosphazene (L) towards divalent metal ions is described. The reaction of L with hydrated metal nitrates afforded [{N3P3(O-C5H4N-3)6}2{Zn(H2O)3(NO3)}2{Zn(H2O)2(NO3)}2]n[NO3]2n·4nH2O·nCH3OH (1), [{N3P3(O-C5H4N-3)6}2{Zn(H2O)3(NO3)}2{Cu(NO3)}2]n[NO3]2n·4nH2O·nCH3CN (2), [{N3P3(O-C5H4N-3)6}2{(NO3)Cd-(μ-(NO3)-Cd(NO3)2(μ-(NO3)Cd(NO3)}]n·2nCH3OH·3nH2O (3), and [{N3P3(O-C5H4N-3)6}2{Cd(H2O)3(NO3)}2][NO3]2·9H2O (4). 1 and 2 are one-dimensional coordination polymers while 3 is a two-dimensional coordination polymer. On the other hand 4 is a molecular metallamacrocycle. A common feature of 1–4 is the presence of a 20-membered dimetallamacrocyclic motif constructed through the involvement of a pair of cyclophosphazene ligands through their geminal pyridyloxy substituents. The P–N bond distances in L and its metal complexes 1–4 are nearly the same indicating the flexible nature of the coordination pyridyloxy arms present on the cyclophosphazene scaffold.
