Co-reporter:Irina A. Kühne, Kieran Griffiths, Amy-Jayne Hutchings, Oliver P. E. Townrow, Andreas Eichhöfer, Christopher E. Anson, George E. Kostakis, and Annie K. Powell
Crystal Growth & Design October 4, 2017 Volume 17(Issue 10) pp:5178-5178
Publication Date(Web):July 11, 2017
DOI:10.1021/acs.cgd.7b00648
From an investigation of varying the steric bulk of a flexible ligand, we have produced a family of structures using similar reaction conditions. Even small changes from a hydrogen atom to a methyl to an ethyl group on the ligand influences the structural outcome, which can also be steered by the nature of the metal source. We employed Schiff base ligands by combining o-vanillin and three different 2-amino-1,3-propandiol units, leading to H3L1 (R = hydrogen), H3L2 (R = methyl), and H3L3 (R = ethyl). The differing nuclearities of the three clusters, 1–3, originate mainly from the steric influence, while this effect is not seen in complexes 4–6, where the general butterfly motif is maintained. We present here the synthesis, crystal structures, and magnetic properties of six new CuII-LnIII complexes, providing valuable insight into future synthetic directions. The topological part includes a table of all CuII–DyIII complexes with nuclearities higher than four and their topological motif. The investigation of the magnetic behaviors reveals that all six complexes show frequency dependent signals in the out-of phase ac susceptibility, which is indicative for single molecule magnets behavior.
Co-reporter:Hong-Guang Jin, Xiaoqin Jiang, Irina A. Kühne, Sylvain Clair, Valérie Monnier, Christophe Chendo, Ghenadie Novitchi, Annie K. Powell, Karl M. Kadish, and Teodor Silviu Balaban
Inorganic Chemistry May 1, 2017 Volume 56(Issue 9) pp:4864-4864
Publication Date(Web):April 13, 2017
DOI:10.1021/acs.inorgchem.6b03056
Five heteroleptic lanthanide porphyrin–bis-phthalocyanine triple-decker complexes with bulky peripheral groups were prepared via microwave-assisted synthesis and characterized in terms of their spectroscopic, electrochemical, and magnetic properties. These compounds, which were easily obtained under our preparative conditions, would normally not be accessible in large quantities using conventional synthetic methods, as a result of the low yield resulting from steric congestion of bulky groups on the periphery of the phthalocyanine and porphyrin ligands. The electrochemically investigated triple-decker derivatives undergo four reversible one-electron oxidations and three reversible one-electron reductions. The sites of oxidation and reduction were assigned on the basis of redox potentials and UV–vis spectral changes during electron-transfer processes monitored by thin-layer spectroelectrochemistry, in conjunction with assignments of electronic absorption bands of the neutral compounds. Magnetic susceptibility measurements on two derivatives containing TbIII and DyIII metal ions reveal the presence of ferromagnetic interactions, probably resulting from magnetic dipolar interactions. The TbIII derivative shows SMM behavior under an applied field of 0.1 T, where the direct and Orbach process can be determined, resulting in an energy barrier of Ueff = 132.0 K. However, Cole–Cole plots reveal the presence of two relaxation processes, the second of which takes place at higher frequencies, with the data conforming to a 1/t ∝ T7 relation, thus suggesting that it can be assigned to a Raman process. Attempts were made to form two-dimensional (2D) self-assembled networks on a highly oriented pyrolytic graphite (HOPG) surface but were unsuccessful due to bulky peripheral groups on the two Pc macrocycles.
Co-reporter:Sebastian F. M. Schmidt, Changhyun Koo, Valeriu Mereacre, Jaena Park, Dieter W. Heermann, Vladislav Kataev, Christopher E. Anson, Denis Prodius, Ghenadie Novitchi, Rüdiger Klingeler, and Annie K. Powell
Inorganic Chemistry May 1, 2017 Volume 56(Issue 9) pp:4796-4796
Publication Date(Web):February 10, 2017
DOI:10.1021/acs.inorgchem.6b02682
We present the synthesis, structure, magnetic properties, as well as the Mössbauer and electron paramagnetic resonance studies of a ring-shaped [FeIII4LnIII2(Htea)4(μ-N3)4(N3)3(piv)3] (Ln = Y 1, Gd 2, Tb 3, Dy 4, Ho 5, Er, 6) coordination cluster. The Dy, Tb, and Ho analogues show blocking of the magnetization at low temperatures without applied fields. The anisotropy of the 3d ion and the exchange interaction between 3d and 4f ions in Fe4Ln2 complexes are unambiguously determined by high-field/high-frequency electron paramagnetic resonance measurements at low temperature. Ferromagnetic exchange interaction JFe–Ln is found which decreases upon variation of the Ln ions to larger atomic numbers. This dependence is similar to the behavior shown in the effective barrier values of complexes 3–5. Further information about the anisotropy of the Ln3+ ions was gathered with 57Fe Mössbauer spectroscopy, and the combination of these methods provides detailed information regarding the electronic structure of these complexes.
Co-reporter:Ahmed S. Abouelwafa, Andreas Hauser, Valeriu Mereacre, Yanhua Lan, Gary J. Long, Fernande Grandjean, Gernot Buth, Christopher E. Anson, and Annie K. Powell
Inorganic Chemistry June 5, 2017 Volume 56(Issue 11) pp:6477-6477
Publication Date(Web):May 16, 2017
DOI:10.1021/acs.inorgchem.7b00540
K3Fe(CN)6 reacts with the viologen 1,1′-bis(2,4-dinitrophenyl)-4,4′-bipyridinium dication, (DNP)2+, to form a supramolecular complex, (DNP)3[Fe(CN)6]2·10H2O (1). The crystal structure of 1 reveals that there are two [Fe(CN)6]3– anions within an organic framework of three (DNP)2+ cations with the shortest Fe(III)···Fe(III) distances of ca. 9.8 Å, distances that minimize extensive long-range magnetic exchange coupling interactions between the [Fe(CN)6]3– anions, and, thus, 1 is paramagnetic above ca. 17 K and exhibits weak ferromagnetic coupling between 17 and 3 K and antiferromagnetic coupling between 3 and 1.8 K. The long Fe(III)···Fe(III) distances permit slow spin–spin and slow spin–lattice paramagnetic relaxation, relative to the iron-57 Larmor precession frequency, as is evidenced by the Mössbauer spectra measured between 3 and 60 K; between 85 and 295 K, rapid paramagnetic relaxation is observed. Both the slow spin–spin and slow spin–lattice relaxation are mediated by the organic, π-conjugated viologen cations. The Fe–C distances, the Mössbauer isomer shifts, the temperature dependence of the magnetic susceptibility, and the 3 K magnetization results all indicate the presence of low-spin Fe(III) ions in the [Fe(CN)6]3– anions in 1. There is no unequivocal indication of the presence of any formal electron delocalization or transfer from the [Fe(CN)6]3– anion to the (DNP)2+ cations in the results obtained from X-ray crystallography, magnetic measurements, and Mössbauer spectra. Because of enhancement of the spin–orbit coupling by the heavy-atom or -ion effect, the Fe(III) ions in the [Fe(CN)6]3– anions interact with the (DNP)2+ cations, causing them to fluoresce with increasing intensity upon cooling from 90 to 25 K when excited at 300 nm. The resulting luminescence of the viologen (DNP)2+ cation induced by the [Fe(CN)6]3– anions indicates the presence of significant mixing of the molecular orbitals derived from the [Fe(CN)6]3– anions and the molecular orbitals associated with the (DNP)2+ cations to yield bonding supramolecular orbitals in 1, a mixing that is also observed between 50 and 3 K in the temperature dependence of the isomer shift of 1.
Co-reporter:Yan Peng, Valeriu Mereacre, Christopher E. Anson, Yiquan Zhang, Tilmann Bodenstein, Karin Fink, and Annie K. Powell
Inorganic Chemistry June 5, 2017 Volume 56(Issue 11) pp:6056-6056
Publication Date(Web):May 9, 2017
DOI:10.1021/acs.inorgchem.6b02743
Three air-stable Co(II) mononuclear complexes with different aromatic substituents have been prepared and structurally characterized by single-crystal X-ray diffraction. The mononuclear complexes [Co(H2L1)2]·2THF (1), [Co(HL2)2] (2), and [Co(H2L3)2]·CH2Cl2 (3) (where H3L1, H2L2, and H3L3 represent 3-hydroxy-naphthalene-2-carboxylic acid (6-hydroxymethyl-pyridin-2-ylmethylene) hydrazide, nicotinic acid (6-hydroxymethyl-pyridin-2-ylmethylene) hydrazide, and 2-hydroxy-benzoic acid (6-hydroxymethyl-pyridin-2-ylmethylene) hydrazide, respectively) feature a distorted mer octahedral coordination geometry. Detailed magnetic studies of 1–3 have been conducted using direct and alternating current magnetic susceptibility data. Field-induced slow magnetic relaxation was observed for these three complexes. There are few examples of such behavior in (distorted) octahedral coordination geometry (OC) Co(II) mononuclear complexes with uniaxial anisotropy. Analysis of the six-coordinate Co(II) mononuclear single-ion magnets (SIMs) in the literature using the SHAPE program revealed that they all show what is best described as distorted trigonal prismatic (TRP) coordination geometry, and in general, these show negative D zero-field splitting (ZFS) values. On the other hand, all the Co(II) mononuclear complexes displaying what is best approximated as distorted octahedral (OC) coordination geometry show positive D values. In the new Co(II) mononuclear complexes we describe here, there is an ambiguity, since the rigid tridentate ligands confer what is best described for an octahedral complex as a mer coordination geometry, but the actual shape of the first coordination sphere is between octahedral and trigonal prismatic. The negative D values observed experimentally and supported by high-level electronic structure calculations are thus in line with a trigonal prismatic geometry. However, a consideration of the rhombicity as indicated by the E value of the ZFS in conjunction with the SHAPE analysis shows that in this case it is difficult to distinguish between the OC and TRP descriptions.
Co-reporter:Yan Peng;Valeriu Mereacre;Christopher E. Anson
Dalton Transactions 2017 vol. 46(Issue 16) pp:5337-5343
Publication Date(Web):2017/04/19
DOI:10.1039/C7DT00548B
Three defect-dicubane coordination clusters related to our previously reported butterfly compound, [Co2Dy2(L)4(NO3)2(THF)2]·4THF (1) and formulated as [Co2Dy2(L)4(NO3)2(MeOH)2]·2CH2Cl2 (2), [Co2Dy2(L)4(NO3)2(DMF)2]·2C2H6CO (3) and [Zn2Dy2(L)4(NO3)2(MeOH)2]·2CH2Cl2 (4) were synthesised and characterised. All show typical SMM behaviour which is steered through the nature of the solvent molecule coordinated to the central 3d ions. The ZnII2DyIII2, (4) provides experimental proof of the suggestion that in such CoII2DyIII2 compounds two major relaxation pathways can be important in determining the overall magnetic behaviour of CoII-4f systems.
Co-reporter:Sihuai Chen;Valeriu Mereacre;George E. Kostakis;Christopher E. Anson
Inorganic Chemistry Frontiers 2017 vol. 4(Issue 6) pp:927-934
Publication Date(Web):2017/06/13
DOI:10.1039/C7QI00091J
Four isostructural MIII4LnIII2 coordination clusters, [M4Ln2(μ3-OH)2(nbdea)4(C6H5COO)8]·MeCN (M = Fe, Ln = Er (1); M = Ga, Ln = Er (2); M = Fe, Ln = Ho (3); M = Ga, Ln = Ho (4)) have been synthesized and characterized. Single-crystal X-ray diffraction and X-ray powder diffraction studies revealed that all four compounds crystallize isomorphously to each other, and to the previously reported MIII4DyIII2 (M = Fe or Ga) and FeIII4YIII2 analogues. DC magnetic susceptibility measurements for compounds 1–4, taken in combination with those for the FeIII4YIII2 analogue, indicated that the interactions between ErIII ions are weakly ferromagnetic and the FeIII–ErIII interactions are very weakly antiferromagnetic, while the HoIII–HoIII and FeIII–HoIII interactions are both negligible. By comparison, for the FeIII4DyIII2 analogue, the DyIII–DyIII interactions are antiferromagnetic while the FeIII–DyIII are ferromagnetic. Both Er analogues 1 and 2 display single-molecule magnet (SMM) behavior with the effective energy barrier Ueff increasing from 12.8 K (for Fe4Er21) to 53.5 K (for Ga4Er22), indicating that the very weak 3d–4f interaction enhances the QTM effect.
Co-reporter:Nicolas Leblanc;Damiano Genovese;Luisa De Cola
Physical Chemistry Chemical Physics 2017 vol. 19(Issue 10) pp:6981-6988
Publication Date(Web):2017/03/08
DOI:10.1039/C6CP07538J
The N,N′-dimethyl-3,3′-biquinoxalinium “methylbiquinoxen” dicationic platform is revealed to have even more fascinating possibilities than we originally thought in terms of its chemical versatility. In addition to its rich redox chemistry and coordination abilities, we have now unveiled an unexpected Lewis acid/base chemistry linked with a tuneable switching of its luminescence properties. This, amongst other things, allows for the facile fluorescent covalent labelling of hydroxyl-terminated materials. This platform provides intriguing chemical prospects realised in molecular systems such as porphyrins as well as an easy alternative functionalisation methodology to that provided by click-chemistry.
Co-reporter:Nicolas Leblanc;Stephen Sproules
New Journal of Chemistry (1998-Present) 2017 vol. 41(Issue 8) pp:2949-2954
Publication Date(Web):2017/04/10
DOI:10.1039/C7NJ00531H
An alternative synthetic route for the design of N,N′-diquaternised-3,3′-biquinoxalinium “biquinoxen” dications is reported, involving oxidative radical coupling of dithionite reduced quinoxaline quaternary salts. Although the reaction is not regioselective, leading to relatively modest yields (up to 32%), the advantages of this new synthetic protocol lie in a simple potentially gram scale synthesis using inexpensive easily accessible reagents with no metal catalysts and no purification steps. Thus whereas the method reported previously to access the N,N′-dimethyl-3,3′-biquinoxalinium, “methylbiquinoxen” precursor gave higher yield than the new method reported here, this new method avoids the limitation of using scarce oxonium reagents. Overall, the new protocol is a robust synthetic strategy which offers new design possibilities.
Co-reporter:Sebastian F. M. Schmidt;Marcel P. Merkel;George E. Kostakis;Gernot Buth;Christopher E. Anson
Dalton Transactions 2017 vol. 46(Issue 45) pp:15661-15665
Publication Date(Web):2017/11/21
DOI:10.1039/C7DT03149A
We present the synthesis and characterization of heterometallic compounds with a very large azide to metal ratio. Their interesting structures give rise to fascinating magnetic properties.
Co-reporter:Muhammad Nadeem Akhtar;Yanhua Lan
Monatshefte für Chemie - Chemical Monthly 2017 Volume 148( Issue 5) pp:887-891
Publication Date(Web):2017 May
DOI:10.1007/s00706-016-1820-9
A new mixed-valent Mn–Ln complex with an Mn9IIIMn2IILa2 core \( [{\text{Mn}}_{9}^{\text{III}} {\text{Mn}}_{2}^{\text{II}} {\text{La}}_{ 2} (\mu_{ 4} {-}{\text{O}})_{7} (\mu_{ 3} {-}{\text{O}})(\mu_{ 3} {-}{\text{OH}})_{ 2} ({\text{benzoate}})_{ 1 8} ({\text{NO}}_{3} )({\text{MeCN}})] \) has been synthesized. Its magnetic characterization reveals a complex with dominating slow relaxation. In addition, alternating current (ac) susceptibility measurements reveal a frequency-dependent out-of-phase (χ′′M) signal below 4 K, suggesting the complex to be a single-molecule magnet.
Co-reporter:Nicolas Leblanc, Stephen Sproules, Karin Fink, Lionel Sanguinet, Olivier Alévêque, Eric Levillain, Patrick Rosa and Annie K. Powell
Chemical Science 2016 vol. 7(Issue 6) pp:3820-3828
Publication Date(Web):24 Feb 2016
DOI:10.1039/C5SC04904K
To intimately combine a chelating ligand function with the numerous properties of a viologen-like redox-active centre would offer a rare possibility to design controllable multi-redox states, whose properties arise from strongly correlated phenomena between the organic ligand as well as with any metalloid coordinated centres. Such a concept previously proved to be feasible, however is not widely applicable owing to challenges in terms of synthesis, isolation, and aerial sensitivity of both the ligand and its metal complexes. Here we report the first stable example of such a redox-active molecule, N,N′-dimethyl-3,3′-biquinoxalinium2+/˙+/0 “methylbiquinoxen, MBqn2+/˙+/0”, which shows a rich redox chemistry and chelates a metal ion in the case of the metal complex [CdCl2(MBqn0)]. This goes beyond what is possible to achieve using viologens, which are limited by not providing chelation as well as having no accessible biradicaloid state, corresponding to the neutral direduced MBqn0 open-shell behaviour we observe here.
Co-reporter:Irina A. Kühne, Valeriu Mereacre, Christopher E. Anson and Annie K. Powell
Chemical Communications 2016 vol. 52(Issue 5) pp:1021-1024
Publication Date(Web):13 Nov 2015
DOI:10.1039/C5CC08887A
We report a family of isostructural nonanuclear FeIII–LnIII cyclic coordination clusters [FeIII6LnIII3(μ-OMe)9(vanox)6(benz)6]. (Ln = Tb (1), Dy (2), Ho (3), Er (4), Tm (5), Yb (6), Lu (7), Y (8) and Gd (9)), containing an odd number of metal ions. The planar cyclic coordination cluster cores are built up from three [Fe2Ln] subunits.
Co-reporter:Irina A. Kühne, George E. Kostakis, Christopher E. Anson, and Annie K. Powell
Inorganic Chemistry 2016 Volume 55(Issue 9) pp:4072-4074
Publication Date(Web):April 20, 2016
DOI:10.1021/acs.inorgchem.6b00490
We describe the concept of increasing the nuclearity of a previously reported high-spin Cu5Gd2 core using a “fine-tuning” ligand approach. Thus, two Cu9Ln2 coordination clusters, with Ln = Dy (1) and Gd (2), were synthesized with the Gd compound having a ground spin state of 17/2 and the Dy analogue showing single-molecule-magnet behavior in zero field.
Co-reporter:Ionut Mihalcea, Mauro Perfetti, Francesco Pineider, Lorenzo Tesi, Valeriu Mereacre, Fabrice Wilhelm, Andrei Rogalev, Christopher E. Anson, Annie K. Powell, and Roberta Sessoli
Inorganic Chemistry 2016 Volume 55(Issue 20) pp:10068-10074
Publication Date(Web):July 13, 2016
DOI:10.1021/acs.inorgchem.6b01010
We report here the determination of the helical spin structure of three Ln-based chiral chains of the formula [Ln(Hnic)(nic)2(NO3)]n (Hnic = nicotinic acid; Ln = Tb, Dy, and Er) by means of cantilever torque magnetometry. While the Dy and Er derivatives are strongly axial (easy-axis and easy-plane anisotropy, respectively), the Tb derivative is characterized by a remarkable rhombicity. In agreement with these findings, alternating-current susceptibility reveals slow magnetic relaxation only in the Dy derivative. Dilution of DyIII ions in the diamagnetic Y-based analogue shows that the weak ferromagnetic intrachain interactions do not contribute significantly to the energy barrier for the reversal of magnetization, which is better described as a single-ion process. Single crystals of the two enantiomers of the Dy derivative have also been investigated using hard X-ray synchrotron radiation at the L-edge of the metal revealing optical activity although with negligible involvement of the 4f electrons of the DyIII ion.
Co-reporter:Yan Peng, Valeriu Mereacre, Amer Baniodeh, Yanhua Lan, Martin Schlageter, George E. Kostakis, and Annie K. Powell
Inorganic Chemistry 2016 Volume 55(Issue 1) pp:68-74
Publication Date(Web):December 11, 2015
DOI:10.1021/acs.inorgchem.5b01793
The synthesis and characterization of three Dy2 compounds, [Dy2(HL1)2(NO3)4] (1), [Dy2(L2)2(NO3)4] (2), and [Dy2(HL3)2(NO3)4] (3), formed using related tripodal ligands with a central tertiary amine bearing picolyl and alkoxy arms, 2-[(2-hydroxy-ethyl)-pyridin-2-ylmethylamino]-ethanol (H2L1), 2-(bis-pyridin-2-ylmethylamino)-ethanol (HL2), and 2-(bis-pyridin-2-ylmethylamino)-propane-1,3-diol (H2L3), are reported. The compounds are rare examples of alkoxide-bridged {Dy2} complexes and display capped square antiprism coordination geometry around each DyIII ion. Changes in the ligand field environment around the DyIII ions brought about through variations in the ligand donors can be gauged from the magnetic properties, with compounds 1 and 2 showing antiparallel coupling between the DyIII ions and 3 showing parallel coupling. Furthermore, slow relaxation of the magnetization typical of SMM behavior could be observed for compounds 2 and 3, suggesting that small variations in the ligand field can have a significant influence on the slow relaxation processes responsible for SMM behavior of DyIII-based systems.
Co-reporter:Yan Peng, Valeriu Mereacre, Christopher E. Anson and Annie K. Powell
Physical Chemistry Chemical Physics 2016 vol. 18(Issue 31) pp:21469-21480
Publication Date(Web):05 Jul 2016
DOI:10.1039/C6CP02942F
A [DyFeIII2Dy(μ3-OH)2(pmide)2(p-Me-PhCO2)6] coordination cluster, where pmideH2 = N-(2-pyridylmethyl)iminodiethanol, has been synthesized and the magnetic properties studied. The dc magnetic measurements reveal dominant antiferromagnetic interactions between the metal centres. The ac measurements reveal zero-field quantum tunnelling of the magnetisation (QTM) which can be understood, but not adequately modelled, in terms of at least three relaxation processes when appropriate static (dc) fields are applied. To investigate this further, 57Fe Mössbauer spectroscopy was used and well-resolved nuclear hyperfine structures could be observed, showing that on the Mössbauer time scale, without applied field or else with very small applied fields, the iron nuclei experience three or more superhyperfine fields arising from the slow magnetisation reversal of the strongly polarized fields of the DyIII ions.
Co-reporter:Sihuai Chen, Valeriu Mereacre, Christopher E. Anson and Annie K. Powell
Dalton Transactions 2016 vol. 45(Issue 22) pp:9336-9344
Publication Date(Web):10 May 2016
DOI:10.1039/C6DT01364C
The compounds of the system [M4M′2(μ3-OH)2(nbdea)4(C6H5CO2)8]·MeCN, where M = GaIII, M′ = DyIII (2), M = FeIII, M′ = YIII (3) are isostructural to the known [Fe4Dy2] compound (1). Those of the system [M4M′4(μ3-OH)4(nbdea)4(m-CH3C6H4CO2)12]·nMeCN, where M = GaIII, M′ = DyIII, n = 4 (5), M = FeIII, M′ = YIII, n = 1 (6) are isostructural to the [Fe4Dy4] compound (4). This allows for comparisons between single ion effects of the paramagnetic ions. The structures were determined using single crystal analysis. Magnetic susceptibility measurements reveal that the GaIII–DyIII compounds 2 and 5 are SMMs. The energy barrier for 2 is close to that for the known isostructural Fe4Dy2 compound (1), but with a significantly increased relaxation time.
Co-reporter:Sihuai Chen, Valeriu Mereacre, Christopher E. Anson and Annie K. Powell
Dalton Transactions 2016 vol. 45(Issue 1) pp:98-106
Publication Date(Web):04 Nov 2015
DOI:10.1039/C5DT03909F
Two series of heterometallic FeIII–LnIII compounds, [FeIII4LnIII2(μ3-OH)2(mdea)4(m-NO2C6H4COO)8]·3MeCN where Ln = Y (1) and Dy (2) and [FeIII6LnIII3(μ4-O)3(μ3-O)(mdea)5(m-NO2C6H4COO)9]·3MeCN where Ln = Y (3) and Dy (4), were synthesized. Compounds 1 and 2 were obtained under ambient conditions, whereas 3 and 4 were obtained via a solvothermal transformation process by heating 1 or 2 at 120 °C in MeCN. The magnetic properties of all four compounds have been measured and show that compounds 2 and 4 containing DyIII ions exhibit slow relaxation of magnetization characteristic of Single Molecule Magnetic (SMM) behaviour.
Co-reporter:Nicolas Leblanc, Stephen Sproules, Claude Pasquier, Pascale Auban-Senzier, Helene Raffy and Annie K. Powell
Chemical Communications 2015 vol. 51(Issue 64) pp:12740-12743
Publication Date(Web):18 Jun 2015
DOI:10.1039/C5CC04142B
A novel 1D hybrid salt (MQ)[CuBr2]∞ (MQ = N-methylquinoxalinium) is reported. Structural, spectroscopic and magnetic investigations reveal a minimal CuII doping of less than 0.1%. However it is not possible to distinguish CuI and CuII. The unusually close packing of the organic moieties and the dark brown colour of the crystals suggest a defect electronic structure.
Co-reporter:Irina A. Kühne, George E. Kostakis, Christopher E. Anson and Annie K. Powell
Chemical Communications 2015 vol. 51(Issue 13) pp:2702-2705
Publication Date(Web):02 Jan 2015
DOI:10.1039/C4CC09469G
[CuII27(μ4-O)2(OH)13(OMe)7(vanox)10(NO3)8(OH2)2(MeOH)7](NO3)2·2H2O·11MeOH (1) was synthesised from Cu(NO3)2·3H2O and o-vanillin-oxime. Structural analysis shows a molecule composed of a Cu18 “folded-sheet” motif linked to a Cu9 bridging unit. The cluster is highly frustrated and has an S = 1/2 spin ground state.
Co-reporter:Munendra Yadav; Valeriu Mereacre; Sergei Lebedkin; Manfred M. Kappes; Annie K. Powell;Peter W. Roesky
Inorganic Chemistry 2015 Volume 54(Issue 3) pp:773-781
Publication Date(Web):September 19, 2014
DOI:10.1021/ic5014957
The Schiff-base (2-aminoethyl)hydroxybenzoic acid (H2L) as a proligand was prepared in situ from 3-formylsalicylic acid and ethanolamine (ETA). The mononuclear {[Y(HL)4][ETAH]·H2O} (1) and {[Dy(HL)4] [ETAH]·3MeOH·H2O} (2) and tetranuclear {[Y4(HL)2(L)4(μ3-OH)2]·4MeOH·4H2O} (3), {[Dy4(HL)2(L)4(μ3-OH)2]·5(MeOH)2·7H2O (4), and {[Dy4(HL)8(L)2]·4MeOH·2H2O}(5) rare-earth metal complexes of this ligand could be obtained as single-crystalline materials by the treatment of H2L in the presence of the metal salts [Ln(NO3)3·(H2O)m] (Ln = Y, Dy). In the solid state, the tetranuclear compounds 3 and 4 exhibit butterfly structures, whereas 5 adopts a rectangular arrangement. Electrospray ionization mass spectrometry data of the ionic compounds 1 and 2 support single-crystal X-ray analysis. The yttrium compounds 1 and 3 show fluorescence with 11.5% and 13% quantum yield, respectively, whereas the quantum yield of the dysprosium complex 4 is low. Magnetic studies on the dysprosium compounds 4 and 5 suggest the presence of weak antiferromagnetic interactions between neighboring metal centers. Compound 4 shows single-molecule-magnet behavior with two relaxation processes, one with the effective energy barrier Ueff = 84 K and the preexponential factor τ0 = 5.1 × 10–9 s.
Co-reporter:Sihuai Chen; Valeriu Mereacre; Denis Prodius; George E. Kostakis
Inorganic Chemistry 2015 Volume 54(Issue 7) pp:3218-3227
Publication Date(Web):March 6, 2015
DOI:10.1021/ic502809y
In the recently established field of 3d/4f coordination cluster (CC) chemistry several burning questions still need to be addressed. It is clear that combining 3d and 4f metal ions within a coordination cluster core has the potential to lead to electronic structures that will be very difficult to describe but can also be extremely interesting. Furthermore, understanding why certain core topologies seem to be favored is difficult to predict. Here we show that the secondary coordination sphere provided by the ligands influences the favored product, as demonstrated for the compound [Fe4Dy2(μ3-OH)2(n-bdea)4(C6H5CO2)8]·MeCN (1), which has a 2Fe:2Dy:2Fe core and was made using [FeIII3O(C6H5)CO2)(L)3]+ as starting material plus Dy(NO3)3 and N-n-butyl-diethanolamine (n-bdeaH2), compared with the compound made using a methyl meta-substituent (R) on the phenyl ring of the benzoate, [FeIII3O(C6H4Me)CO2)(L)3]+ as starting material, which resulted in the “square-in-square” compound [Fe4Dy4(μ3-OH)4(n-bdea)4(O2CC6H4CH3)12]·MeCN (2) when using ambient conditions. Changing reaction conditions from ambient to solvothermal leads to “double-propeller” compounds [Fe4Dy4(μ4-O)3(n-bdea)3(C6H5CO2)12]·13MeCN (3) and [Fe4Dy4(μ4-O)3(n-bdea)3(O2CC6H4CH3)12]·MeCN (4) forming with this core, resulting irrespective of the substitution on the iron benzoate starting material. Furthermore, compounds 1 and 2 can be transformed into compounds 3 and 4, respectively, using a solvothermal method. Thus, compounds 3 and 4 appear to be the thermodynamically most stable species. The factors steering the reactions toward these products are discussed. The electronic structures have been investigated using magnetic and Mössbauer studies. All compounds are cooperatively coupled 3d/4f systems, with compound 1 showing single-molecule magnet behavior.
Co-reporter:Julia Rinck; Yanhua Lan; Christopher E. Anson
Inorganic Chemistry 2015 Volume 54(Issue 7) pp:3107-3117
Publication Date(Web):March 10, 2015
DOI:10.1021/ic502930p
Reactions of the N-substituted diethanolamine ligand N-n-butyldiethanolamine with chromium(II) and lanthanide(III)/rare earth salts (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y) in the presence of coligands give access to three series of isostructural 1:1 3d(CrIII)/4f(LnIII) coordination cluster compounds that can be designated in terms of octanuclear “square-in-square” (Ln = La–Tb), hexanuclear “triangle-in-triangle” (Ln = Dy, Ho, Y) and tetranuclear “butterfly” or defect dicubane core (Ln = Er–Lu) topologies as revealed by single-crystal X-ray crystallographic analysis. The bulk magnetic properties were also measured. The influences of the various components in the reaction system on the final topology and the role of the ionic radius are discussed.
Co-reporter:Munendra Yadav; Abhishake Mondal; Valeriu Mereacre; Salil Kumar Jana; Annie K. Powell;Peter W. Roesky
Inorganic Chemistry 2015 Volume 54(Issue 16) pp:7846-7856
Publication Date(Web):July 28, 2015
DOI:10.1021/acs.inorgchem.5b00899
The Schiff-base proligand 4-tert-butyl-2,6-bis-[(2-hydroxy-phenylimino)methyl]phenol (H3L) was prepared in situ from 4-tert-butyl-2,6-diformylphenol and 2-aminophenol. The proligand (H3L) was used with dibenzoylmethane (DBMH) or acetylacetone (acacH) with lanthanides giving compounds with varying arrangements of metal atoms and nuclearities. The tetranuclear compound {[Dy4(L)3(DBM)4][Et3NH]} (1) and pentanuclear compound {[Dy5(μ3-OH)2(L)3(DBM)4(MeOH)4]·4(MeOH)} (2) were obtained from the ligand (L)3– and dibenzoylmethane. The tetranuclear compounds {[Dy4(μ4-OH)(L)2(acac)4(MeOH)2(EtOH)(H2O)]·(NO3)·2(MeOH)·3(EtOH)} (3) and {[Ln4(μ3-OH)2(L)(HL)(acac)5(H2O)] (HNEt3)(NO3)·2(Et2O)} (Ln = Tb (4), Dy (5), Ho (6), and Tm (7)) resulted when the ligand (L)3– was used in the presence of acetylacetone. In the solid state structures, the tetranuclear compound 1 adopts a linear arrangement of metal atoms, while tetranuclear compound 3 has a square grid arrangement of metal atoms, and tetranuclear compounds 4–7 have a seesaw-shaped arrangement of metal atoms. The composition found from single-crystal X-ray analysis of compound 1 and 3–7 is supported by electrospray ionization mass spectrometry (ESI-MS). The magnetic studies on compounds 1 suggest the presence of weak ferromagnetic interactions, whereas compounds 2–6 exhibit weak antiferromagnetic interactions between neighboring metal centers. Compounds 1, 2, and 3 also show single-molecule magnet behavior under an applied dc field.
Co-reporter:Masooma Ibrahim, Ali Haider, Yixian Xiang, Bassem S. Bassil, Akina M. Carey, Lisa Rullik, Geoffrey B. Jameson, Floriant Doungmene, Israël M. Mbomekallé, Pedro de Oliveira, Valeriu Mereacre, George E. Kostakis, Annie K. Powell, and Ulrich Kortz
Inorganic Chemistry 2015 Volume 54(Issue 13) pp:6136-6146
Publication Date(Web):June 12, 2015
DOI:10.1021/acs.inorgchem.5b00124
The tetrameric, multi-FeIII-containing polyoxotungstates [Fe14O6(OH)13(P2W15O56)4]31– (1) and [Na2Fe14(OH)12(PO4)4(A-α-XW9O34)4]20– (X = SiIV (2), GeIV (3)) have been successfully synthesized under conventional reaction conditions in aqueous, slightly acidic (1), or basic (2 and 3) media. Polyanions 1-3 were characterized in the solid state by single-crystal X-ray diffraction, IR spectroscopy, thermogravimetric analysis, and magnetic studies, and in solution by electrochemistry.
Co-reporter:Nikolaos C. Anastasiadis, Christina D. Polyzou, George E. Kostakis, Vlasoula Bekiari, Yanhua Lan, Spyros P. Perlepes, Konstantis F. Konidaris and Annie K. Powell
Dalton Transactions 2015 vol. 44(Issue 46) pp:19791-19795
Publication Date(Web):14 Oct 2015
DOI:10.1039/C5DT03663A
The first use of methyl 2-pyridyl ketone oxime (mpkoH) in zinc(II)/lanthanide(III) chemistry leads to the [ZnLn(mpko)3(mpkoH)3](ClO4)2 and [ZnLn(NO3)2(mpko)3(mpkoH)] families of dinuclear ZnIILnIII complexes displaying blue-green, ligand-based photoluminescence; the ZnIIDyIII compound shows field-induced relaxation of magnetization.
Co-reporter:Amer Baniodeh, Nicola Magnani, Stefan Bräse, Christopher E. Anson and Annie K. Powell
Dalton Transactions 2015 vol. 44(Issue 14) pp:6343-6347
Publication Date(Web):02 Mar 2015
DOI:10.1039/C5DT00237K
Two new examples of Dy6 cyclic coordination clusters have been synthesised in order to discover how the toroidal moment in such a motif can be tuned and optimised.
Co-reporter:Christina D. Polyzou, Amer Baniodeh, Nicola Magnani, Valeriu Mereacre, Nicolas Zill, Christopher E. Anson, Spyros P. Perlepes and Annie K. Powell
RSC Advances 2015 vol. 5(Issue 14) pp:10763-10767
Publication Date(Web):06 Jan 2015
DOI:10.1039/C4RA15458D
The first use of the cyanoacetate ligand in 3d/4f-metal chemistry leads to {Fe2IIIM4III} (M = Dy, Gd, Y) coordination clusters with a squashed octahedral core structure unprecedented in Fe/4f compounds; the DyIII compound exhibits slow relaxation of the magnetisation.
Co-reporter:Amer Baniodeh;Yu Liang;Christopher E. Anson;Nicola Magnani;Andreas-Neil Unterreiner;Simon Seyfferle;Michael Slota;Martin Dressel;Lapo Bogani;Karin Goß
Advanced Functional Materials 2014 Volume 24( Issue 40) pp:6280-6290
Publication Date(Web):
DOI:10.1002/adfm.201400336
We investigated the electronic properties of the molecular magnetic nanotoruses [FeIII 10LnIII 10(Me-tea)10(Me-teaH)10(NO3)10], examining the dependence on the lanthanide (Ln) of both the intra and intermolecular electronic channels. Using femtosecond absorption spectroscopy we show that the intramolecular electronic channels follow a three-step process, which involves vibrational cooling and crossing to shallow states, followed by recombination. A comparison with the energy gaps showed a relationship between trap efficiency and gaps, indicating that lanthanide ions create trap states to form excitons after photo-excitation. Using high-resistance transport measurements and scaling techniques, we investigated the intermolecular transport, demonstrating the dominant role of surface-limited transport channels and the presence of different types of charge traps. The intermolecular transport properties can be rationalized in terms of a hopping model, and a connection is provided to the far-IR spectroscopic properties. Comparison between intra and intermolecular processes highlights the role of the excited electronic states and the recombination processes, showing the influence of Kramers parity on the overall mobility.
Co-reporter:Denis Prodius, Hamid Saeed Shah, Jamshed Iqbal, Anastasia Macaeva, Anatoli Dimoglo, George E. Kostakis, Nicolas Zill, Fliur Macaev and Annie K. Powell
Chemical Communications 2014 vol. 50(Issue 38) pp:4888-4890
Publication Date(Web):29 Jan 2014
DOI:10.1039/C3CC49759C
Conversion of nitriles under mild conditions leads to a new class of primary amines, including room temperature ionic liquids, acting as efficient anticancer agents.
Co-reporter:Irina A. Kühne, Nicola Magnani, Valeriu Mereacre, Wolfgang Wernsdorfer, Christopher E. Anson and Annie K. Powell
Chemical Communications 2014 vol. 50(Issue 15) pp:1882-1885
Publication Date(Web):21 Nov 2013
DOI:10.1039/C3CC46458J
The structure and magnetic properties of an octanuclear coordination cluster with a {CuII4DyIII4} core are described and a model for the unusual SMM behaviour is proposed.
Co-reporter:Ayuk M. Ako, Yanhua Lan, Oliver Hampe, Eduard Cremades, Eliseo Ruiz, Christopher E. Anson and Annie K. Powell
Chemical Communications 2014 vol. 50(Issue 44) pp:5847-5850
Publication Date(Web):11 Apr 2014
DOI:10.1039/C4CC01264J
Experimental and theoretical studies indicate that achieving the maximum possible ground spin state of ST = 83/2 for the mixed-valent Mn19 coordination cluster is insensitive to replacement of its eight μ3-N3 ligands by μ3-Cl, μ3-Br, μ3-OH or μ3-OMe, substantiating that the ferromagnetic interactions are indeed mediated mainly by the internal (μ4-O) ligands. The robustness of the inorganic {MnIII12MnII7(μ4-O)8} core is clear from the molecular structure and ESI-MS studies have shown that the structure of the Mn19 aggregate, and also of its Mn18Y analogue, are stable beyond the solid state.
Co-reporter:Ionut Mihalcea, Nicolas Zill, Valeriu Mereacre, Christopher E. Anson, and Annie K. Powell
Crystal Growth & Design 2014 Volume 14(Issue 9) pp:4729-4734
Publication Date(Web):August 8, 2014
DOI:10.1021/cg500827u
A series of homochiral lanthanide nicotinate helical coordination polymers [LnIII(nic)2(Hnic)(NO3)] (Ln = Eu (1), Gd (2), Tb (3); Hnic = nicotinic acid) has been solvothermally synthesized using nicotinic acid. In the resulting chains, chirality is not induced by a chiral agent but appears spontaneously via intrachain hydrogen bondings. Compounds 2 and 3 were magnetically characterized, and luminescent properties were observed for compounds 1 and 3.
Co-reporter:Samir Mameri;Ayuk M. Ako;Fatma Yesil;Marcel Hibert;Yanhua Lan;Christopher E. Anson
European Journal of Inorganic Chemistry 2014 Volume 2014( Issue 26) pp:4326-4334
Publication Date(Web):
DOI:10.1002/ejic.201402327
Abstract
A series of 2,6-bis(hydroxymethyl)-4-R-phenol ligands (H3LR; R = H, F, Cl, Br, I, Ph, NH2, NO2, SMe) have either been newly synthesized or the existing syntheses have been significantly improved to investigate ligand-functionalized analogues of the previously published coordination cluster [MnIII12MnII7(μ4-O)8(μ3-N3)8(HLMe)12(MeCN)6]Cl2·10MeOH·MeCN (1) with S = 83/2. The crystal structures and magnetic properties of three such Mn19 clusters, namely, [MnIII12MnII7(μ4-O)8(HLH)12(μ3-Cl)7(μ3-OMe)(MeOH)6]Cl2·16H2O·10MeOH·MeCN (3), [MnIII12MnII7(μ4-O)8(HLI)12(μ3-N3)8(MeOH)6](O2CH)2·16MeOH·10MeCN (4) and [MnIII12MnII7(μ4-O)8(μ3-Cl)7.7(μ3-OMe)0.3(HLSMe)12(MeOH)6]Cl2·27MeOH (5) are reported and compared to those of the parent cluster. When these ligands are functionalized with substituents of moderate electronegativity, it is possible to synthesize Mn19 analogues; however, when such ligands bear highly electron-donating (amino) or -withdrawing (nitro) substituents, the Mn19 analogues are no longer accessible. The Mn19 cluster framework is both magnetically and structurally robust with respect to the electron-donor/acceptor characteristics of the ligand substituent; therefore, the Mn19 system is an excellent platform for peripheral chemical engineering.
Co-reporter:Dr. Guo Peng;Dr. Valeriu Mereacre;Dr. George E. Kostakis;Dr. Juliusz A. Wolny;Dr. Volker Schünemann;Dr. Annie K. Powell
Chemistry - A European Journal 2014 Volume 20( Issue 39) pp:12381-12384
Publication Date(Web):
DOI:10.1002/chem.201403792
Abstract
Two [FeLn2Fe(μ3-OH)2(teg)2(N3)2(C6H5COO)4] compounds (where Ln=YIII and DyIII; teg=triethylene glycol anion) have been synthesized and studied using SQUID and Mössbauer spectroscopy. The magnetic measurements on both compounds indicate dominant antiferromagnetic interactions between the metal centers. Analysis of the 57Fe Mössbauer spectra complement the ac magnetic susceptibility measurements, which show how a static magnetic field can quench the slow relaxation of magnetization generated by the anisotropic DyIII ions.
Co-reporter:Jun-Liang Liu;Jie-Yi Wu;Yan-Cong Chen;Dr. Valeriu Mereacre;Dr. Annie K. Powell;Dr. Liviu Ungur;Dr. Liviu F. Chibotaru;Dr. Xiao-Ming Chen;Dr. Ming-Liang Tong
Angewandte Chemie 2014 Volume 126( Issue 47) pp:13180-13184
Publication Date(Web):
DOI:10.1002/ange.201407799
Abstract
Eine Rekord-Anisotropiebarriere (319 cm−1) unter sämtlichen d-f-Komplexen wurde für einen einzigartigen FeII-DyIII-FeII-Einzelmolekülmagneten (single molecule magnet, SMM) gefunden, der zwei asymmetrische und verzerrte FeII-Ionen und ein quasi-D5h-symmetrisches DyIII-Ion enthält. Die eingefrorene Magnetisierung der DyIII-Ionen führt zur verlangsamten Relaxation der FeII-Ionen, die im Mößbauer-Spektrum beobachtet wird. Ab-initio-Rechnungen legen nahe, dass ein Tunneln durch Austauschdubletts erfolgreich unterbrochen wird.
Co-reporter:Jun-Liang Liu;Jie-Yi Wu;Yan-Cong Chen;Dr. Valeriu Mereacre;Dr. Annie K. Powell;Dr. Liviu Ungur;Dr. Liviu F. Chibotaru;Dr. Xiao-Ming Chen;Dr. Ming-Liang Tong
Angewandte Chemie International Edition 2014 Volume 53( Issue 47) pp:12966-12970
Publication Date(Web):
DOI:10.1002/anie.201407799
Abstract
A record anisotropy barrier (319 cm−1) for all d-f complexes was observed for a unique FeII-DyIII-FeII single-molecule magnet (SMM), which possesses two asymmetric and distorted FeII ions and one quasi-D5h DyIII ion. The frozen magnetization of the DyIII ion leads to the decreased FeII relaxation rates evident in the Mössbauer spectrum. Ab initio calculations suggest that tunneling is interrupted effectively thanks to the exchange doublets.
Co-reporter:Gang Wu ; Jiaquan Bai ; Yuan Jiang ; Guanghua Li ; Jian Huang ; Yi Li ; Christopher E. Anson ; Annie K. Powell ;Shilun Qiu
Journal of the American Chemical Society 2013 Volume 135(Issue 49) pp:18276-18279
Publication Date(Web):November 21, 2013
DOI:10.1021/ja409569q
Target synthesis of metal–organic nanotubes (MONTs) through a classic “rolling-up” mechanism remains a big challenge for coordination chemists. In this work, we report three 2D lamellar compounds and one (4,0) zigzag MONT based on a common honeycomb coordination skeleton. Our synthetic strategy toward sheet/tube superstructure transformation is to asymmetrically modify the inter-layer interactions by gradually increasing the size of the amine templates. Eventually, to relieve the surface tension of individual layers and to enhance surface areas and optimize host–guest interactions to accommodate bigger guests, spontaneous rolling up to form a tubular structure was achieved.
Co-reporter:Amer Baniodeh, Christopher E. Anson and Annie K. Powell
Chemical Science 2013 vol. 4(Issue 12) pp:4354-4361
Publication Date(Web):29 Aug 2013
DOI:10.1039/C3SC52041B
Five [FeIIImYbIIIn] Cyclic Coordination Clusters (CCCs) which show completely different arrangements of their cyclic cores have been synthesised and characterised. These represent five out of seven compounds which were obtained by fine-tuning the reaction conditions (FeIII-source, LnIII-salt, chiral/nonchiral aminoalcohol ligands) used previously to synthesise the non-cyclic [Fe2Yb2(OH)2(teaH)2(O2CPh)6] compound 1. Thus the five new CCCs [Fe5Yb3(μ3-OH)(teaH)7(O2CPh)8](CF3SO3)·10MeCN (m = 5; n = 2, 2), [Fe4Yb2(μ-OH)(μ-OMe)2(Me-teaH)4(O2CPh)7]·3CH3CN (m = 4; n = 2, 3), [Fe3Yb2(μ-OH)(Me-teaH)4(O2CPh)6]·MeCN (m = 3; n = 2, 4), [Fe4Yb2(Me-tea)4(Me-teaH)2(OTs)2]·MeCN·3MeOH (m = 4; n = 2, 5) and [Fe10Yb10(Me-tea)10(Me-teaH)10(NO3)10]·21MeCN (m = 10; n = 10, 6) as well as the binuclear complex [Yb2(tipH2)2(O2CPh)4] (7) are reported. The formation of compounds 2, 3 and 4, which were obtained using [Fe3O(O2CCPh)6(H2O)3]+ as the source of FeIII, can be rationalised in terms of cleaving the triangular {FeIII3O} starting material into mononuclear and dinuclear FeIII/benzoate species. Furthermore, it was found that for compounds 3–6, the interplay of ligand chirality, hydrogen-bonding interactions and the nature of anionic species present are decisive directional influences on the resulting nature of the cyclic compounds.
Co-reporter:Denis Prodius, Fliur Macaev, Eugenia Stingaci, Vsevolod Pogrebnoi, Valeriu Mereacre, Ghenadie Novitchi, George E. Kostakis, Christopher E. Anson and Annie K. Powell
Chemical Communications 2013 vol. 49(Issue 19) pp:1915-1917
Publication Date(Web):22 Oct 2012
DOI:10.1039/C2CC36741F
A new class of task-specific ionic liquids (ILs) which contain septuply positively charged {Fe3IIIO(RCOO)6L3}7+ triangles has been synthesized and structurally characterized. Such metal-containing ILs can be repeatedly used as alternative catalysts in the synthesis of 2-pyrrolo-3′-yloxindole or the condensation of indoles with various aldehydes.
Co-reporter:Hua Xiang, Valeriu Mereacre, Yanhua Lan, Tong-Bu Lu, Christopher E. Anson and Annie K. Powell
Chemical Communications 2013 vol. 49(Issue 67) pp:7385-7387
Publication Date(Web):09 May 2013
DOI:10.1039/C3CC42416B
[FeIII2LnIII2(OH)2(L1)2(HL2)2(NO3)4(H2O)1½(MeOH)½]·6MeCN (Ln = Y (1), Dy (2); H2L1 = 2,3-dihydroxybenzaldehyde and H2L2 is the Schiff base of this aldehyde with furfurylamine) have unusually weak antiferromagnetic interactions between the FeIII centres in comparison with other (μ-dihydroxo)diiron(III) complexes. For 1, it was established that modulation of the hydroxo bridges by coordination to the YIII ions results in long Fe–O bonds and small Fe–O–Fe angles, leading to J = −0.4 cm−1. Analysis of the Mössbauer spectra reveals that the intramolecular magnetic field generated by the anisotropic DyIII ions in 2 is sufficient to overcome the Fe–Fe antiferromagnetic coupling and reorientate the FeIII moments into a ferromagnetic spin orientation.
Co-reporter:Denis Prodius, Fliur Macaev, Yanhua Lan, Ghenadie Novitchi, Serghei Pogrebnoi, Eugenia Stingaci, Valeriu Mereacre, Christopher E. Anson and Annie K. Powell
Chemical Communications 2013 vol. 49(Issue 80) pp:9215-9217
Publication Date(Web):07 Aug 2013
DOI:10.1039/C3CC45554H
Dysprosium based ionic liquids displaying slow relaxation of magnetization at low temperatures are reported.
Co-reporter:Amer Baniodeh, Valeriu Mereacre, Nicola Magnani, Yanhua Lan, Juliusz A. Wolny, Volker Schünemann, Christopher E. Anson and Annie K. Powell
Chemical Communications 2013 vol. 49(Issue 83) pp:9666-9668
Publication Date(Web):21 Aug 2013
DOI:10.1039/C3CC45695A
The modulation of the magnetic anisotropy using the electronic features of the ligands was monitored by performing magnetic, spectroscopic and theoretical studies on a series of {Fe2Dy2} coordination clusters.
Co-reporter:Sebastian Schmidt, Denis Prodius, Valeriu Mereacre, George E. Kostakis and Annie K. Powell
Chemical Communications 2013 vol. 49(Issue 17) pp:1696-1698
Publication Date(Web):06 Dec 2012
DOI:10.1039/C2CC38006D
A nonanuclear {Fe6Dy3} coordination cluster displaying SMM behaviour in which an unprecedented chemical transformation provides structural information for the existence of 1,1,2,2-tetrahydroxyethane is reported.
Co-reporter:Ayuk M. Ako, Boris Burger, Yanhua Lan, Valeriu Mereacre, Rodolphe Clérac, Gernot Buth, Silvia Gómez-Coca, Eliseo Ruiz, Christopher E. Anson, and Annie K. Powell
Inorganic Chemistry 2013 Volume 52(Issue 10) pp:5764-5774
Publication Date(Web):May 7, 2013
DOI:10.1021/ic3025588
We previously reported how the synthesis of [MnIII12MnII7(μ4-O)8(μ3-η1-N3)8(HL1)12(MeCN)6]Cl2·10MeOH·MeCN (1), which has a Mn19 core corresponding to two supertetrahedral {MnII4MnIII6} units sharing a common MnII vertex, can be modified such that the central octacoordinate MnII ion can be replaced by metal ions more likely to favor this coordination geometry such as DyIII as exemplified in the compound [MnIII12MnII6DyIII(μ4-O)8(μ3-Cl)6.5(μ3-N3)1.5(HL)12(MeOH)6]Cl3·25MeOH (2). Here, we report a systematic survey of the effects of incorporating various diamagnetic metal ions Mn+ into this central position. We chose diamagnetic ions with electron configurations with fully occupied or completely empty frontier orbitals in order to gauge the effect on the overall magnetic behavior. The syntheses, structures, and magnetic properties of the heterometallic aggregates [MnIII12MnII6SrII(μ4-O)8(μ3-η1-N3)7.5(μ3-η1-Cl)0.5(HL1)12(MeCN)6]Cl2·15MeOH (3), [MnIII12MnII6YIII(μ4-O)8(μ3-η1-N3)8(HL1)12(MeCN)6](NO3)3·11MeOH (4), [MnIII12MnII6CdII(μ4-O)8(μ3-η1-N3)6.8(μ3-η1-Cl)1.2(HL1)12(MeCN)6](CdCl4)0.25Cl1.5·14.5MeOH (5), and [MnIII12MnII6LuIII(μ4-O)8(μ3-η1-N3)6.5(μ3-η1-Cl)1.5(HL2)12(MeCN)6]Cl3·3H2O·7MeOH·MeCN (6) (H3L1 = 2,6-bis(hydroxymethyl)-4-methylphenol, H3L2 = 2,6-bis(hydroxymethyl)-4-fluorophenol) are reported. The aggregates were prepared in one-pot self-assembly reactions of H3L1 (or H3L2), MnCl2·4H2O or Mn(NO3)2·4H2O, NaOAc·3H2O or Et3N, and NaN3 in the presence of the appropriate diamagnetic metal salt in MeCN/MeOH mixtures. Compounds 3–6 crystallize isotypically to 1 in the trigonal space group R3̅ with Z = 3. The effects on the magnetic properties were investigated, paying attention to the presence of any weak coupling mediated by the diamagnetic cations between the two {MnII3MnIII6} S = 39/2 subunits. In the Cd2+ compound 5, the two {MnII3MnIII6} units are magnetically isolated. In 3, 4, and 6, the diamagnetic Sr2+, Y3+, and Lu3+ cations mediate weak antiferromagnetic interactions between the two {MnII3MnIII6} subunits. DFT calculations show that the inter-{MnII3MnIII6} interactions in the Mn18M systems are attributable to the electronic structure of the central diamagnetic cation, with systems containing trivalent central cations showing stronger antiferromagnetic interactions than those with isoelectronic divalent cations.
Co-reporter:Masooma Ibrahim, Yixian Xiang, Bassem S. Bassil, Yanhua Lan, Annie K. Powell, Pedro de Oliveira, Bineta Keita, and Ulrich Kortz
Inorganic Chemistry 2013 Volume 52(Issue 15) pp:8399-8408
Publication Date(Web):July 19, 2013
DOI:10.1021/ic400943j
The two Ni2+-containing heteropolytungstates [Ni14(OH)6(H2O)10(HPO4)4(P2W15O56)4]34– (Ni14) and [Ni5(OH)4(H2O)4(β-GeW9O34)(β-GeW8O30(OH))]13– (Ni5) have been successfully synthesized in aqueous, basic media under conventional reaction conditions, and they were characterized by single-crystal X-ray diffraction, IR spectroscopy, thermogravimetric and elemental analyses, electrochemistry, and magnetic studies. The cyclic voltammetry (CV) patterns of Ni14 and Ni5 showed chemically reversible multielectronic waves for slow scan time scales. For Ni14, an important acidity inversion effect between its reduced forms was observed. Magnetic studies revealed dominant ferromagnetic interactions among the nickel(II) ions in both polyanions.
Co-reporter:Ghulam Abbas ; Yanhua Lan ; Valeriu Mereacre ; Gernot Buth ; Moulay T. Sougrati ; Fernande Grandjean ; Gary J. Long ; Christopher E. Anson
Inorganic Chemistry 2013 Volume 52(Issue 20) pp:11767-11777
Publication Date(Web):October 3, 2013
DOI:10.1021/ic401011d
The reaction of N-methydiethanolamine (mdeaH2), benzoic acid, FeCl3, and Ln(NO3)3·6H2O or LnCl3·xH2O yields a series of decanuclear coordination clusters, [Ln3Fe7(μ4-O)2(μ3-OH)2(mdea)7(μ-benzoate)4(N3)6]·4MeCN·H2O, where Ln = GdIII (1) or TbIII (2), and [Er3Fe7(μ4-O)2(μ3-OH)2(mdea)7(μ-benzoate)4(N3)5(MeOH)]Cl·7.5H2O·11.5MeOH (3). The isostructural compounds 1–3 all crystallize isotypically in the triclinic space group P1̅ with Z = 2, as does the previously reported dysprosium analogue 4. Six of the FeIII ions are pseudooctahedrally coordinated, whereas the seventh has a trigonal-bipyramidal coordination geometry. Temperature-dependent direct-current magnetic susceptibility studies indicate that intracluster antiferromagnetic interactions are dominant in 1–3. The frequency-dependent out-of-phase (χ″) alternating-current susceptibility reveals that 2 undergoes a slow relaxation of its magnetization, presumably resulting from anisotropy of the TbIII ions. Between 30 and 295 K, the 57Fe Mössbauer spectra reveal paramagnetic behavior with six partially resolved quadrupole doublets, one for the trigonal-bipyramidal FeIII site and five for the six pseudooctahedral FeIII sites. The Mössbauer spectra of 2 and 3 obtained between 3 and 30 K are consistent with the presence of FeIII intracluster antiferromagnetic coupling with slow magnetic relaxation relative to the Larmor precession time. Further, the observed changes in the effective magnetic field values in the spectra measured at 3 K with increasing applied field are consistent with the effect of the local spin polarization along the applied magnetic field direction, a behavior reminiscent of antiparallel spin-coupled iron molecular paramagnetic systems.
Co-reporter:Dominique T. Thielemann, Anna T. Wagner, Yanhua Lan, Christopher E. Anson, Michael T. Gamer, Annie K. Powell and Peter W. Roesky
Dalton Transactions 2013 vol. 42(Issue 41) pp:14794-14800
Publication Date(Web):29 Aug 2013
DOI:10.1039/C3DT50133G
The synthesis and characterization of three chiral and one achiral amino acid anion ligated dysprosium hydroxo clusters [Dy5(OH)5(α-AA)4(Ph2acac)6] (α-AA = D-PhGly, L-Pro, L-Trp, Ph2Gly; Ph2acac = dibenzoylmethanide) are reported. The solid state structures were determined using single crystal X-ray diffraction and show that five Dy(III) ions are arranged in a square-based pyramidal geometry with NO7-donor-sets for the basal and O8-donor-sets for the apical Dy atom. Both static (dc) and dynamic (ac) magnetic properties were investigated for all four compounds and show a slow relaxation of magnetization, indicative of single molecule magnet (SMM) behaviour below 10 K in all cases. The similar SMM behaviour observed for all four compounds suggests that the very similar coordination geometries seen for the dysprosium atoms in all members of this family, which are independent of the amino acid ligand used, play a decisive role in steering the contribution of the single ion anisotropies to the observed magnetic relaxation.
Co-reporter:Noelia M. Sanchez-Ballester, Lok Kumar Shrestha, Mark R. J. Elsegood, Wolfgang Schmitt, Katsuhiko Ariga, Christopher E. Anson, Jonathan P. Hill and Annie K. Powell
Dalton Transactions 2013 vol. 42(Issue 8) pp:2779-2785
Publication Date(Web):04 Dec 2012
DOI:10.1039/C2DT32547K
A dinuclear manganese(III) complex (1) of an N-(carboxymethyl)-N-[3,5-bis(α,α-dimethylbenzyl-2-hydroxybenzyl)]glycine (HDA) ligand (L) binds a manganese(II) species through displacement of its solvating ligands by appropriately dispositioned carbonyl groups of a dinuclear complex {[Mn2(L)2(OH)(OCH3)][Mn(H2O)3(CH3OH)3], 2, triclinic P, a = 13.172(3) Å, b = 15.897(3) Å, c = 19.059(4) Å, V = 3461.9(13) Å3} leading to a trinuclear complex {3, monoclinic P21/n, a = 11.7606(8) Å, b = 21.3505(8) Å, c = 26.7827(17) Å, V = 6722.7(7) Å3} with cyclization of two of the carboxy groups through the doubly-carboxy group coordinated Mn2+ ion. The reaction is discussed in terms of its significance as an illustration of how Mn2+ ions might be sequestered in biological systems. A similar solvato-ligand displacement reaction was used to synthesise coordination polymers of an HDA iron(III) complex involving polymerization through a bridging carboxylato group. Several isostructural polymers (5–7; for 5: orthorhombic Pbca, a = 9.411(5) Å, b = 16.390(8) Å, c = 37.968(19) Å, V = 5856(5) Å3) with different coordinated alcohols could be prepared indicating the potential synthetic uses of this method.
Co-reporter:Konstantin V. Shuvaev, Stephen Sproules, J. Mikko. Rautiainen, Eric J. L. McInnes, David Collison, Christopher E. Anson and Annie K. Powell
Dalton Transactions 2013 vol. 42(Issue 7) pp:2371-2381
Publication Date(Web):11 Sep 2012
DOI:10.1039/C2DT31946B
A novel multitopic, two-pocket ligand HLnitnitnitnit, containing the nitronyl nitroxide radical, has been designed for a self-assembled [2 × 2] grid system. HLnitnitnitnit is not stable in methanol and slowly undergoes a disproportionation, during which the nitronyl nitroxide radical converts to the diamagnetic amidino oxide. In situ reaction of HLnitnitnitnit with Cu(BF4)2 in methanol depending on the reaction time affords self-assembled [2 × 2] grids (Lnitnitnitnit)2(L)2Cu(II)4(BF4)4·CH3OH (1) or (Lnitnitnitnit)0.5(L)3.5Cu(II)4(BF4)4·CH3OH (2), in which L contains an amidino oxide arising from a 3-electron reduction of the nitronyl nitroxide radical. The percentages of stable radical in grids 1 and 2 as determined by X-ray are 50 and 12.5%, respectively. Structures 1 and 2 contain a six-coordinated distorted Cu(II) that is oxo-bridged at 140°. The nitronyl nitroxide radical coordinates via the oxo-atom of the N+–O− fragment in a chelating fashion and lies in the equatorial plane of the metal ion. The magnetic properties of 1 could be fitted to a 5-spin Hamiltonian with JCu–Cu = +3.1 cm−1 and JCu–Nit = −278 cm−1, while those of 2 to a 4-spin Hamiltonian with JCu–Cu = +2.9 cm−1. The Q-band EPR spectra of 1 and 2 recorded in solution at 20 K showed intricate anisotropic features of the Cu(II) ion and a much weaker signal of the –NO˙ fragment, associated with a strong Cu(II)–Nit antiferromagentic coupling. The DFT calculated (B3LYP/TZVP/6-31G*) magnetic coupling constants for the grid of 1 were JCu–Cu = +5 cm−1 and JCu–Nit = −282 cm−1, which are in very good agreement with the experimentally obtained values.
Co-reporter:Guo Peng, George E. Kostakis, Yanhua Lan and Annie K. Powell
Dalton Transactions 2013 vol. 42(Issue 1) pp:46-49
Publication Date(Web):04 Sep 2012
DOI:10.1039/C2DT32027D
The first use of triethylene glycol (H2teg) in Fe/Ln chemistry affords two series of tetranuclear {FeIII2LnIII2} coordination clusters possessing defect-dicubane cores. A change in the synthetic procedure results in a different arrangement of the relative positions of the 3d and 4f elements offering a means to steer the structural and electronic features within a 3d–4f system.
Co-reporter:Amer Baniodeh, Yanhua Lan, Ghenadie Novitchi, Valeriu Mereacre, Andrey Sukhanov, Marilena Ferbinteanu, Violeta Voronkova, Christopher E. Anson and Annie K. Powell
Dalton Transactions 2013 vol. 42(Issue 24) pp:8926-8938
Publication Date(Web):28 Mar 2013
DOI:10.1039/C3DT00105A
The reaction of [Fe3O(O2CPh)6(H2O)3](O2CPh) with lanthanide/rare earth nitrate salts in the presence of triethanolamine (H3tea) in acetonitrile/methanol solution yields a series of compounds with isostructural tetranuclear core motifs [FeIII2LnIII2(μ3-OH)2(teaH)2(O2CCPh)6]·3MeCN (Ln = Ce (1), Pr (2), Nd (3), Sm (4), Eu (5), Gd (6), Tb (7), Dy (8), Ho (9), Er (10), Tm (11), Yb (12), Y (13)). In all cases the core topology is a defect-dicubane planar or “butterfly” Fe2Ln2 motif. Compounds 1–13 were investigated using a combination of experimental techniques and theoretical studies. Magnetic susceptibility measurements were carried out on all compounds. The magnetic coupling between the two FeIII centres is antiferromagnetic, with JFeFeca. −6.71(4) cm−1, while the Fe–Ln couplings are much weaker, e.g. JFeGd = 0.18(1) cm−1. Compounds 6, 7, 8 and 13 were selected for Mössbauer studies in order to investigate the influence of isotropic (GdIII), highly anisotropic non-Kramers and Kramers (TbIII and DyIII) and diamagnetic (YIII) rare earth ions on the local environment of the FeIII centres. Compounds 3, 6, 8 and 13 were also studied using X-Band EPR spectroscopy. For 13, with the diamagnetic YIII ion, this made it possible to obtain the D, E, JFeFe and g parameters for the iron centres. It is shown that the low-temperature spectra of compounds 3, 6 and 8 are determined by magnetic properties of rare-earth ions and the dipole–dipole interactions between the LnIII ions. The Fe–Ln interactions were confirmed as very weak and dipolar in nature by the temperature dependence of EPR spectra at T > 20 K.
Co-reporter:Ayuk M. Ako, Yanhua Lan, Valeriu Mereacre, Eliseo Ruiz, Daniel Aravena, Christopher E. Anson and Annie K. Powell
Dalton Transactions 2013 vol. 42(Issue 26) pp:9606-9612
Publication Date(Web):15 Apr 2013
DOI:10.1039/C3DT50345C
The synthesis of the high-nuclearity FeIII14 coordination cluster [Fe14(μ3-O)6(μ3-OH)4(μ-OH)3Cl11(dea)4(Hdea)3]Cl·H2O·27MeCN (1) is reported (in which deaH2 = diethanolamine). X-ray crystallographic analysis revealed that compound 1 crystallises in the cubic space group Im with Z = 24 and 8 independent Fe centres. Unusually for an FeIII coordination cluster, the FeIII centres in 1 adopt a range of 4, 5 and 6 coordinate geometries. Complex 1 presents a ferracalixarene topology which can be described in terms of a “half tennis ball” structure and binds a chloride anion guest via multiple hydrogen bonds. The curvature in the structure induced by this topology affects the overall spin structure. A ground spin state of S = 7 is proposed using a combination of magnetic susceptibility data and density functional theory (DFT) calculations.
Co-reporter:Franziska Völcker, Yanhua Lan, Annie K. Powell and Peter W. Roesky
Dalton Transactions 2013 vol. 42(Issue 32) pp:11471-11475
Publication Date(Web):05 Jul 2013
DOI:10.1039/C3DT51078F
Two homoleptic phosphanylamido dysprosium complexes [Li(THF)4][(Ph2PNPh)4Dy] and [Dy{N(PPh2)2}3] have been synthesized. Both have a highly symmetric arrangement of the ligand which is only slightly broken in the solid state by steric and packing effects as a result of the weak coordination of phosphorus atoms to the metal centre. Magnetic properties of these two compounds are similar with both showing slow magnetic relaxation.
Co-reporter:Kartik Chandra Mondal, George E. Kostakis, Yanhua Lan, Annie K. Powell
Polyhedron 2013 66() pp: 268-273
Publication Date(Web):
DOI:10.1016/j.poly.2013.05.016
Co-reporter:George E. Kostakis, Spyros P. Perlepes, Vladislav A. Blatov, Davide M. Proserpio, Annie K. Powell
Coordination Chemistry Reviews 2012 Volume 256(11–12) pp:1246-1278
Publication Date(Web):June 2012
DOI:10.1016/j.ccr.2012.02.002
Polynuclear coordination clusters of 3d metals continue to attract the intense interest of scientists from the synthetic inorganic chemistry, bioinorganic chemistry and molecular magnetism communities. In this review we have focused on describing aspects of synthesis, structures and magnetic properties of Co coordination clusters with nuclearities higher than 4. Adopting our recently developed topological approach for the description of coordination clusters, we have classified the structural motifs of Co complexes which range in nuclearity from 5 to 36. Emphasis is given to the magnetic properties of Co coordination clusters. Some of them display slow magnetic relaxation at very low temperatures, mainly due to their large magnetic anisotropies. The possibility of magnetic anisotropies one and two orders of magnitude larger than seen so far for single-molecule magnets of other 3d-metal ions, promises a brilliant future in the research of polynuclear Co complexes.Highlights► We analysed aspects of the synthetic, structural and magnetic chemistry of Co CCs. ► We classified all the polynuclear Co CCs found in CCDC higher than 4. ► All Co CCs can be searched by cluster topological symbol and nuclearity and Refcode.
Co-reporter:Ghenadie Novitchi, Guillaume Pilet, Liviu Ungur, Victor V. Moshchalkov, Wolfgang Wernsdorfer, Liviu F. Chibotaru, Dominique Luneau and Annie K. Powell
Chemical Science 2012 vol. 3(Issue 4) pp:1169-1176
Publication Date(Web):30 Jan 2012
DOI:10.1039/C2SC00728B
The first example of exchange coupling between the toroidal moments in chiral heterometallic CuII/DyIII 1D polymers built from alternating trinuclear Dy3 SMM-building blocks and chiral copper(II) complexes is reported. A very strong toroidal magnetization can be induced by applying a magnetic field at low temperature in single-crystals of these compounds.
Co-reporter:Sebastian Schmidt, Denis Prodius, Ghenadie Novitchi, Valeriu Mereacre, George E. Kostakis and Annie K. Powell
Chemical Communications 2012 vol. 48(Issue 79) pp:9825-9827
Publication Date(Web):02 Aug 2012
DOI:10.1039/C2CC34361D
A new family of hexanuclear ferric-lanthanide [FeIII4LnIII2(Htea)4(Piv)6(N3)4] clusters, where LnIII = Er(1) and Lu(2) is reported. Variable temperature solid-state magnetic susceptibility studies of 1 and 2 reveal the presence of ferromagnetic (1) or competing anti- and ferromagnetic exchange interactions (2) between the constituent FeIII ions.
Co-reporter:Asamanjoy Bhunia, Michael T. Gamer, Liviu Ungur, Liviu F. Chibotaru, Annie K. Powell, Yanhua Lan, Peter W. Roesky, Fabian Menges, Christoph Riehn, and Gereon Niedner-Schatteburg
Inorganic Chemistry 2012 Volume 51(Issue 18) pp:9589-9597
Publication Date(Web):April 20, 2012
DOI:10.1021/ic300065x
The Schiff base compound 2,2′-{[(2-aminoethyl)imino]bis[2,1-ethanediyl-nitriloethylidyne]}bis-2-hydroxy-benzoic acid (H4L) as a proligand was prepared in situ. This proligand has three potential coordination pockets which make it possible to accommodate from one to three metal ions allowing for the possible formation of mono-, di-, and trinuclear complexes. Reaction of in situ prepared H4L with Dy(NO3)3·5H2O resulted in the formation of a mononuclear complex [Dy(H3L)2](NO3)·(EtOH)·8(H2O) (1), which shows SMM behavior. In contrast, reaction of in situ prepared H4L with Mn(ClO4)2·6H2O and Dy(NO3)3·5H2O in the presence of a base resulted in a trinuclear mixed 3d–4f complex (NHEt3)2[Dy{Mn(L)}2](ClO4)·2(H2O) (2). At low temperatures, compound 2 is a weak ferromagnet. Thus, the SMM behavior of compound 1 can be switched off by incorporating two Mn(II) ions in close proximity either side of the Dy(III). This quenching behavior is ascribed to the presence of the weak ferromagnetic interactions between the Mn(II) and Dy(III) ions, which at T > 2 K act as a fluctuating field causing the reversal of magnetization on the dysprosium ion. Mass spectrometric ion signals related to compounds 1 and 2 were both detected in positive and negative ion modes via electrospray ionization mass spectrometry. Hydrogen/deuterium exchange (HDX) reactions with ND3 were performed in a FT-ICR Penning-trap mass spectrometer.
Co-reporter:Ahmed S. Abouelwafa, Christopher E. Anson, Andreas Hauser, Howard H. Patterson, François Baril-Robert, Xiaobo Li, and Annie K. Powell
Inorganic Chemistry 2012 Volume 51(Issue 3) pp:1294-1301
Publication Date(Web):January 19, 2012
DOI:10.1021/ic201109u
Dicyanoaurate reacts with the organic acceptor molecule, 1,1′-bis-(2,4-dinitrophenyl)-4,4′-bipyridinium, DNP, to form a supramolecular complex with the general formula {[Au(CN)2]2DNP}·4H2O. The complex was characterized by X-ray crystallography, and its photophysical properties were investigated in the solid-state. Although the initial (DNP)Cl2 compound does not show photoluminescence behavior and the dicyanoaurate shows photoluminescence only in the UV range, the resulting supramolecular complex displays two simultaneous, essentially independent, photoluminescence bands in the visible range originating from individual contributions of the DNP unit and the dicyanoaurate dimers. This unusual simultaneous photoluminescence behavior displayed by both the dicyanoaurate donor units and the redox-active 4,4′-bipyridinium acceptor have lifetimes of 0.5 μs and several hundred μs, respectively.
Co-reporter:Humphrey L. C. Feltham, Rodolphe Clérac, Liviu Ungur, Veacheslav Vieru, Liviu F. Chibotaru, Annie K. Powell, and Sally Brooker
Inorganic Chemistry 2012 Volume 51(Issue 20) pp:10603-10612
Publication Date(Web):September 24, 2012
DOI:10.1021/ic300819u
Thirteen tetranuclear mixed-metal complexes of the hexaimine macrocycle (LPr)6– have been prepared in a one-pot 3:1:3:3 reaction of copper(II) acetate hydrate, the appropriate lanthanide(III) nitrate hydrate, 1,4-diformyl-2,3-dihydroxybenzene (1), and 1,3-diaminopropane. The resulting family of copper(II)–lanthanide(III) macrocyclic complexes has the general formula CuII3LnIII(LPr)(NO3)3·solvents (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Tb, Ho, Er, Tm, or Yb). X-ray crystal structure determinations carried out on [Cu3Ce(LPr)(NO3)3(MeOH)3] and [Cu3Dy(LPr)(NO3)3(MeOH)3] confirmed that the large LnIII ion is bound in the central O6 site and the three square pyramidal CuII ions in the outer N2O2 sites (apical donor either nitrate anion or methanol molecule) of the Schiff base macrocycle. Only the structurally characterized Cu3Tb complex, reported earlier, is a single-molecule magnet (SMM): the other 12 complexes do not exhibit an out-of-phase ac susceptibility signal or hysteresis of magnetization in a dc field. Ab initio calculations allowed us to rationalize the observed magnetic properties, including the significant impact of subtle chemical modification on SMM behavior. Broken-symmetry density functional theory (BS-DFT) calculations show there is a subtle structural balance as to whether the Cu···Cu exchange coupling is ferro- or antiferromagnetic. Of the family of 13 magnetically characterized tetranuclear CuII3LnIII macrocyclic complexes prepared, only the TbIII complex is an SMM: the theoretical reasons for this are discussed.
Co-reporter:Konstantis F. Konidaris, Christina D. Polyzou, George E. Kostakis, Anastasios J. Tasiopoulos, Olivier Roubeau, Simon J. Teat, Evy Manessi-Zoupa, Annie K. Powell and Spyros P. Perlepes
Dalton Transactions 2012 vol. 41(Issue 10) pp:2862-2865
Publication Date(Web):28 Nov 2011
DOI:10.1039/C1DT11881A
Metal-ion mediated reactions of 2-pyridinealdoxime and hexafluorophosphate lead to ZnII complexes containing picolinic acid, picolinamide and monofluorophosphate (−2) as ligands.
Co-reporter:Ayuk M. Ako;Mohammad Sahabul Alam;Samir Mameri;Yanhua Lan;Marcel Hibert;Michael Stocker;Paul Müller;Christopher E. Anson
European Journal of Inorganic Chemistry 2012 Volume 2012( Issue 26) pp:4131-4140
Publication Date(Web):
DOI:10.1002/ejic.201200420
Abstract
A structural analogue of the previously reported record-high-spin (S = 83/2) mixed-valence [Mn19] coordination cluster [MnIII12MnII7(μ4-O)8(μ3-η1-N3)8(HLMe)12(MeCN)6]Cl2·10MeOH·MeCN (1) {H3LMe = 2,6-bis(hydroxymethyl)-4-methylphenol} was prepared in which the methyl group at the 4-position on the phenyl ring was replaced by a methoxy group to give the compound [Et3NH]2[MnIII12MnII7(μ4-O)8(μ3-η1-N3)7.4(μ3-Cl)0.6(HLOMe)12(MeOH)6]Cl4·14MeOH (2). Single-crystal X-ray diffraction analysis of 2 confirms that the molecular structure motif found for 1, comprising two supertetrahedral {MnIII6MnII4} units sharing a common MnII vertex, was retained. Magnetic susceptibility measurements on 2 show that the ferromagnetic spin structure, which results in the maximum ST = 83/2 spin ground state for 1, is largely robust with respect to the change in ligand substituent in 2. Molecules of compounds 1 and 2 were deposited onto highly oriented pyrolytic graphite (HOPG) substrates and were investigated by scanning tunneling microscopy (STM) andcurrent imaging tunneling spectroscopy (CITS). By usingextremely dilute solutions (10–9 mol L–1), one-dimensionalarrangements as well as isolated single molecules of [1]Cl2·10MeOH·MeCN were observed with STM topography, generally at the step edges or at defects of the HOPG surfaces, while small groups of molecules of 2 were observed. The size of the individual molecules was consistent with the X-ray crystallographic data. In the CITS images of the single molecules, a strong tunneling current contrast was observed at the positions of the metal ions.
Co-reporter:Dr. Ayuk M. Ako;Dr. Mohammad Sahabul Alam;Mostafizur Rahman;Dr. Jonathan P. Hill;Dr. Noelia M. Sanchez-Ballester;Dr. Katsuhiko Ariga;Dr. Gernot Buth;Dr. Christopher E. Anson;Dr. Annie K. Powell
Chemistry - A European Journal 2012 Volume 18( Issue 51) pp:16419-16425
Publication Date(Web):
DOI:10.1002/chem.201202858
Abstract
The synthesis and structures of the N-[(2-hydroxy-3-methyl-5-dodecylphenyl)methyl]-N-(carboxymethyl)glycine disodium salt (HL) ligand and its neutral mononuclear complex [FeIII(L)(EtOH)2] (1) are reported. Structural and electronic properties of 1 were investigated by using scanning tunneling microscopy (STM) and current imaging tunneling spectroscopy (CITS) techniques. These studies reveal that molecules of 1 form well-ordered self-assemblies when deposited on a highly oriented pyrolytic graphite (HOPG) surface. At low concentrations, single or double chains (i.e., nanowires) of the complex were observed, whereas at high concentration the complex forms crystals and densely packed one-dimensional structures. In STM topographies, the dimensions of assemblies of 1 found on the surface are consistent with dimensions obtained from X-ray crystallography, which indicates the strong similarities between the crystal form and surface assembled states. Double chains are attributed to hydrogen-bonding interactions and the molecules align preferentially along graphite defects. In the CITS image of complex 1 a strong tunneling current contrast at the positions of the metal ions was observed. These data were interpreted and reveal that the bonds coordinating the metal ions are weaker than those of the surrounding ligands; therefore the energy levels next to the Fermi energy of the molecule should be dominated by metal-ion orbitals.
Co-reporter:Dr. Kartik Chra Mondal;Alexer Sundt;Dr. Yanhua Lan;Dr. George E. Kostakis; Oliver Waldmann;Dr. Liviu Ungur;Dr. Liviu F. Chibotaru;Dr. Christopher E. Anson;Dr. Annie K. Powell
Angewandte Chemie International Edition 2012 Volume 51( Issue 30) pp:7550-7554
Publication Date(Web):
DOI:10.1002/anie.201201478
Co-reporter:Valeriu Mereacre ; Amer Baniodeh ; Christopher E. Anson
Journal of the American Chemical Society 2011 Volume 133(Issue 39) pp:15335-15337
Publication Date(Web):August 26, 2011
DOI:10.1021/ja206941e
A series of [Fe2Dy2(OH)2(teaH)2(RC6H4COO)6] compounds has been synthesized and studied using Mössbauer spectroscopy. It is suggested that the local crystal field of the DyIII centers and the external magnetic field can control their shape anisotropy and thus the interactions between the dysprosium and iron centers.
Co-reporter:Valeriu Mereacre ; Yanhua Lan ; Rodolphe Clérac ; Ayuk M. Ako ; Wolfgang Wernsdorfer ; Gernot Buth ⊗; Christopher E. Anson
Inorganic Chemistry 2011 Volume 50(Issue 23) pp:12001-12009
Publication Date(Web):November 2, 2011
DOI:10.1021/ic201322b
The synthesis, structures, and magnetic properties of a family of isostructural “bell-shaped” heterometallic coordination clusters [MnIII9MnII2LaIII2(μ4-O)7(μ3-O)(μ3-OH)2(piv)10.8(O2CC4H3O)6.2(NO3)2(OH2)1.5(MeCN)0.5]·12CH3CN·2H2O (1) and [MnIII9MnII2Ln2(μ4-O)7(μ 3-O)(μ3-OH)2(piv)10.6(O2CC4H3O)6.4(NO3)2(OH2)]·nCH3CN·H2O (Ln = PrIII, n = 8 (2); Ln = NdIII, n = 10 (3); Ln = EuIII, n = 17 (4); Ln = GdIII, n = 13 (5); piv = pivalate) are reported. The complexes were obtained from the reaction of [MnIII2MnII4O2(piv)10(4-Me-py)2.5(pivH)1.5] and Ln(NO3)3·6H2O in the presence of 2-furan-carboxylic acid (C4H3OCOOH) in CH3CN. Compounds 1–5 are isomorphous, crystallizing in the triclinic space group P1̅ with Z = 2. The MnIII and MnII centers together form the shell of the bell, while the two LnIII centers can be regarded as the bell’s clapper. The magnetic properties of 1–4 reveal dominant antiferromagnetic interactions between the magnetic centers leading to small spin ground states; while those of 5 indicate similar antiferromagnetic interactions between the manganese ions but with unusually strong ferromagnetic interactions between the GdIII ions leading to a large overall spin ground state of S = 11–12. While ac and dc magnetic measurements confirmed that Mn11Gd2 (5) is a single-molecule magnet (SMM) showing hysteresis loops at low temperatures, compounds 1–4 do not show any slow relaxation of the magnetization, indicating that the S = 7 spin of the ferromagnetic Gd2 unit in 5 is a necessary contribution to its SMM behavior.
Co-reporter:Asamanjoy Bhunia, Yanhua Lan, Valeriu Mereacre, Michael T. Gamer, Annie K. Powell, and Peter W. Roesky
Inorganic Chemistry 2011 Volume 50(Issue 24) pp:12697-12704
Publication Date(Web):November 14, 2011
DOI:10.1021/ic2018264
Reaction of N,N′-bis(4-carboxysalicylidene)ethylenediamine (H4L) with iron(III) chloride and lanthanide nitrates resulted in the coordination polymers of composition {[Ln2(FeLCl)2(NO3)2(DMF)5]·(DMF)4}n (Ln = Y, Eu, Gd, Tb, Dy). The polymers consist of iron-salen-based moieties having carboxylate linkers connected to rare earth atoms in a 1D chain structure. Thus, the iron-salen complex acts as a “metalloligand”. Because of the twisting of the chains, porous structures are formed and possess large free void space. The magnetic studies of selected compounds exhibit weak intramolecular antiferromagnetic interactions of Ln–Ln. At 3, 30, and 80 K, the Mössbauer spectra of the iron–dysprosium compound show a strongly asymmetric quadrupole doublet with isomer shift and quadrupole splitting values typical for FeIII ions in high spin state. In addition, an anomalous temperature dependence of both isomer shift and quadrupole splitting has been observed.
Co-reporter:Kartik Chandra Mondal ; George E. Kostakis ; Yanhua Lan ; Wolfgang Wernsdorfer ; Christopher E. Anson
Inorganic Chemistry 2011 Volume 50(Issue 22) pp:11604-11611
Publication Date(Web):October 24, 2011
DOI:10.1021/ic2015397
Two pairs of Ni2Dy2 and Ni2Tb2 complexes, [Ni2Ln2(L)4(NO3)2(DMF)2] {Ln = Dy (1), Tb (2)} and [Ni2Ln2(L)4(NO3)2(MeOH)2]·3MeOH {Ln = Dy (3), Tb (4)} (H2L is the Schiff base resulting from the condensation of o-vanillin and 2-aminophenol) possessing a defect-dicubane core topology were synthesized and characterized. All four complexes are ferromagnetically coupled, and the two Dy-analogues are found to be Single Molecule Magnets (SMMs) with energy barriers in the range 18–28 K. Compound 1 displays step-like hysteresis loops, confirming the SMM behavior. Although 1 and 3 show very similar structural topologies, the dynamic properties of 1 and 3 are different with blocking temperatures (3.2 and 4.2 K at a frequency of 1500 Hz) differing by 1 K. This appears to result from a change in orientation of the nitrate ligands on the DyIII ions, induced by changes in ligands on NiII.
Co-reporter:Humphrey L. C. Feltham ; Rodolphe Clérac ; Annie K. Powell ;Sally Brooker
Inorganic Chemistry 2011 Volume 50(Issue 10) pp:4232-4234
Publication Date(Web):April 8, 2011
DOI:10.1021/ic2003639
[CuII3TbIII(LPr)(NO3)2(MeOH)(H2O)2](NO3)·3H2O is a rare example of a 3d−4f single-molecule magnet prepared using a macrocyclic ligand: at low T, it exhibits frequency-dependent alternating-current susceptibility, indicative of slow relaxation of the magnetization.
Co-reporter:Zeeshan Majeed, George E. Kostakis, Yanhua Lan and Annie K. Powell
Dalton Transactions 2011 vol. 40(Issue 45) pp:12210-12216
Publication Date(Web):06 Sep 2011
DOI:10.1039/C1DT10917K
We report herein five new coordination polymers of general formula [LnNa(C6H5CO2)4] where Ln = Y (6), Tb (7), Er (8), [DyNa(CH3CO2)4(MeOH)] (9) and [DyNa(C3H7CO2)4] (10). Single crystal structure analyses revealed that all compounds have a repeating unit containing one Ln3+, one Na+ and four monocarboxylate ligands (RCO2−) (R = –CH3, –C3H7, –C6H5). Compounds 6–8 and 10 possess helical polymeric structures which are extended in three dimensions forming chiral srs networks whilst compound 9 constitutes a two dimensional honeycomb network, illustrating that variation in the alkyl group of the monocarboxylate can result in versatile and variable polymeric networks. The magnetic properties of the reported compounds have also been studied.
Co-reporter:Humphrey L. C. Feltham, Frederik Klöwer, Scott A. Cameron, David S. Larsen, Yanhua Lan, Manuel Tropiano, Stephen Faulkner, Annie K. Powell and Sally Brooker
Dalton Transactions 2011 vol. 40(Issue 43) pp:11425-11432
Publication Date(Web):21 Sep 2011
DOI:10.1039/C1DT11038A
A family of thirteen tetranuclear heterometallic zinc(II)-lanthanide(III) complexes of the hexa-imine macrocycle (LPr)6−, with general formula ZnII3LnIII(LPr)(NO3)3·xsolvents (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm or Yb), were prepared in a one-pot synthesis using a 3:1:3:3 reaction of zinc(II) acetate, the appropriate lanthanide(III) nitrate, the dialdehyde 1,4-diformyl-2,3-dihydroxybenzene (H2L1) and 1,3-diaminopropane. A hexanuclear homometallic zinc(II) macrocyclic complex [Zn6(LPr)(OAc)5(OH)(H2O)]·3H2O was obtained using a 2:0:1:1 ratio of the same reagents. A control experiment using a 1:0:1:1 ratio failed to generate the lanthanide-free [Zn3(LPr)] macrocyclic complex. The reaction of H2L1 and zinc(II) acetate in a 1:1 ratio yielded the pentanuclear homometallic complex of the dialdehyde H2L1, [Zn5(L1)5(H2O)6]·3H2O. An X-ray crystal structure determination revealed [Zn3IIPrIII(LPr)(NO3)2(DMF)3](NO3)·0.9DMF has the large ten-coordinate lanthanide(III) ion bound in the central O6 site with two bidentate nitrate anions completing the O10 coordination sphere. The three square pyramidal zinc(II) ions are in the outer N2O2 sites with a fifth donor from DMF. Measurement of the magnetic properties of [ZnII3DyIII(LPr)(NO3)3(MeOH)3]·4H2O with a weak external dc field showed that it has a frequency-dependent out-of-phase component of ac susceptibility, indicative of slow relaxation of the magnetization (SMM behaviour). Likewise, the Er and Yb analogues are field-induced SMMs; the latter is only the second example of a Yb-based SMM. The neodymium, ytterbium and erbium complexes are luminescent in the solid phase, but only the ytterbium and neodymium complexes show strong lanthanide-centred luminescence in DMF solution.
Co-reporter:Amer Baniodeh, Ian J. Hewitt, Valeriu Mereacre, Yanhua Lan, Ghenadie Novitchi, Christopher E. Anson and Annie K. Powell
Dalton Transactions 2011 vol. 40(Issue 16) pp:4080-4086
Publication Date(Web):09 Mar 2011
DOI:10.1039/C0DT01742F
The reaction of triethanolamine (teaH3) with [FeIII3O(O2CCH3)6(H2O)3]Cl·6H2O and Ln(NO3)3·6H2O in acetonitrile yields [Fe16Ln4(tea)8(teaH)12(μ-O2CCH3)8](NO3)4·16H2O·xMeCN (Ln = Sm (1), Eu (2), Gd (3), Tb (4), Dy (5), Ho (6); x = 10 or 11). These 20-membered metallo-ring complexes are the largest such single-stranded oxygen-bridged rings so far reported. The structure is stabilised by two of the acetate ligands, which form anti,anti-bridges across the centre of the ring, pinching the ring and giving it rigidity. The magnetic properties are dominated by the antiferromagnetic couplings between the FeIII centres. Although the Fe2 and Fe6 sub-chains within the ring are fully spin-compensated at low temperatures with Ssubchain = 0, coupling between the GdIII cations and the FeIII centres at the ends of the sub-chains (in 3) results in a pinning of the lanthanide spins. The 57Fe Mössbauer spectra of 3 and 5 obtained at low temperatures are consistent with the presence of FeIII intracluster strong antiferromagnetic coupling. The applied field spectrum for 3 reveals no magnetic hyperfine interaction apart from that of the nucleus with the applied field, while the one for 5 is a superposition of three subspectra which show contributions from each of the peripheral as well as from the central iron sites.
Co-reporter:Masooma Ibrahim;Dr. Yanhua Lan;Dr. Bassem S. Bassil;Yixian Xiang;Andreas Suchopar; Annie K. Powell; Ulrich Kortz
Angewandte Chemie International Edition 2011 Volume 50( Issue 20) pp:4708-4711
Publication Date(Web):
DOI:10.1002/anie.201100280
Co-reporter:Stefan Stuiber;Dr. Gang Wu;Joscha Nehrkorn;Dr. Jan Dreiser;Dr. Yanhua Lan;Dr. Ghenadie Novitchi;Dr. Christopher E. Anson;Dr. Tobias Unruh;Dr. Annie K. Powell;Dr. Oliver Waldmann
Chemistry - A European Journal 2011 Volume 17( Issue 33) pp:9094-9106
Publication Date(Web):
DOI:10.1002/chem.201100500
Abstract
The synthesis, crystal structure and magnetic characterisation by magnetisation and inelastic neutron scattering (INS) of a mixed-valent Mn10 supertetrahedral aggregate [MnIII6MnII4(μ4-O)4(μ3-N3)3(μ3-Br)(Hmpt)6(Br)]Br0.7(N3)0.3⋅2 MeOH⋅3 MeCN (1) (H3mpt=3-methylpentan-1,3,5-triol) is reported. The magnetic core of the molecule can be described as an octahedron of six S=2 MnIII ions with four faces, each capped by a S=5/2 MnII ion such as to form the supertetrahedron. Unlike most related complexes, the molecular symmetry is slightly reduced from approximately Td to C3. The magnetic data reveal a total spin of S=22 in the ground state due to ferromagnetic exchange couplings within the molecule. The combined INS and magnetic data permits the accurate determination of the exchange coupling constants. Two types are found. The couplings between the MnIII ions in the inner octahedron are characterised by Ja=18.4(3) K, whereas the couplings between the apical MnII ions to the neighbouring MnIII ions are given by Jb=7.3(2) K. The significantly larger coupling strength Ja as compared to Jb, and the near-Td symmetry have profound consequences on the energy spectrum, which are discussed and carefully analysed. In particular, the observed INS spectra can consistently be reproduced by a simplified model in which the inner octahedron is replaced by one large spin of length S0=12. This model provides intuitive insight into the structure of the magnetic spectrum. Additionally, the magnetic excitations at low temperature are analysed within the frame of ferromagnetic linear spin-wave theory, which permits an analytical calculation of the energy levels. For ferromagnetic clusters, a close analogy to the Hückel method of electronic structure calculation can be drawn, which allows one to grasp the results of the spin-wave theory or the magnetic excitation spectrum, respectively, in a chemical language.
Co-reporter:Masooma Ibrahim;Dr. Yanhua Lan;Dr. Bassem S. Bassil;Yixian Xiang;Andreas Suchopar; Annie K. Powell; Ulrich Kortz
Angewandte Chemie 2011 Volume 123( Issue 20) pp:4805-4808
Publication Date(Web):
DOI:10.1002/ange.201100280
Co-reporter:Dr. Valeriu Mereacre;Dr. Denis Prodius;Dr. Yanhua Lan;Dr. Constantin Turta;Dr. Christopher E. Anson;Dr. Annie K. Powell
Chemistry - A European Journal 2011 Volume 17( Issue 1) pp:123-128
Publication Date(Web):
DOI:10.1002/chem.201002060
Co-reporter:Humphrey L. C. Feltham;Dr. Yanhua Lan;Frederik Klöwer ;Liviu Ungur; Liviu F. Chibotaru; Annie K. Powell; Sally Brooker
Chemistry - A European Journal 2011 Volume 17( Issue 16) pp:4362-4365
Publication Date(Web):
DOI:10.1002/chem.201100438
Co-reporter:Dr. Ayuk M. Ako;Dr. Valeriu Mereacre;Dr. Yanhua Lan;Dr. Christopher E. Anson;Dr. Annie K. Powell
Chemistry - A European Journal 2011 Volume 17( Issue 16) pp:4366-4370
Publication Date(Web):
DOI:10.1002/chem.201003574
Co-reporter:Humphrey L. C. Feltham;Dr. Yanhua Lan;Frederik Klöwer ;Liviu Ungur; Liviu F. Chibotaru; Annie K. Powell; Sally Brooker
Chemistry - A European Journal 2011 Volume 17( Issue 16) pp:
Publication Date(Web):
DOI:10.1002/chem.201190081
Co-reporter:Zeeshan Majeed, Kartik C. Mondal, George E. Kostakis, Yanhua Lan, Christopher E. Anson and Annie K. Powell
Chemical Communications 2010 vol. 46(Issue 15) pp:2551-2553
Publication Date(Web):24 Feb 2010
DOI:10.1039/B923998G
We present the surprising result that the combination of the monotopic benzoate ligand with lanthanide ions leads to a 3D network which also possesses the chiral srs-topology.
Co-reporter:Ghulam Abbas, Yanhua Lan, George E. Kostakis, Wolfgang Wernsdorfer, Christopher E. Anson and Annie K. Powell
Inorganic Chemistry 2010 Volume 49(Issue 17) pp:8067-8072
Publication Date(Web):August 12, 2010
DOI:10.1021/ic1011605
A series of five isostructural tetranuclear lanthanide complexes of formula [Ln4(μ3-OH)2(mdeaH)2(piv)8], (mdeaH2 = N-methyldiethanolamine; piv = pivalate; Ln = Tb (1), Dy (2), Ho (3), Er (4), and Tm (5)) have been synthesized and characterized. These clusters have a planar “butterfly” Ln4 core. Magnetically, the LnIII ions are weakly coupled in all cases; the Dy4 compound 2 shows Single Molecule Magnet (SMM) behavior.
Co-reporter:Valeriu Mereacre, Yanhua Lan, Rodolphe Clérac, Ayuk M. Ako, Ian J. Hewitt, Wolfgang Wernsdorfer, Gernot Buth, Christopher E. Anson and Annie K. Powell
Inorganic Chemistry 2010 Volume 49(Issue 11) pp:5293-5302
Publication Date(Web):April 26, 2010
DOI:10.1021/ic100373r
An isostructural family of tetranuclear aggregates [MnIII2Ln2(O)(Piv)2(hep)4(NO3)4]·MeCN (where Ln = YIII (1), PrIII (2), NdIII (3), GdIII (4), TbIII (5), DyIII (6), HoIII (7), and YbIII (8)) is reported. They were obtained from the reactions of 2-(2-hydroxyethyl)pyridine (hepH) with a preformed hexanuclear manganese complex, [Mn6], and the respective lanthanide salt. The complexes are isomorphous and represent a new heterometallic 3d-4f complex type for this class of ligand. The structural core of 1−8 consists of a distorted Mn2Ln2 tetrahedron with the four metal centers linking through a μ4-O2− bridging atom. The magnetic properties of all complexes were investigated by variable temperature magnetic susceptibility and magnetization measurements. The magnetic data of all compounds suggest that antiferromagnetic interactions are present between adjacent paramagnetic centers. Complexes 5−7 containing highly anisotropic lanthanide ions (Tb, Dy, and Ho) show slow relaxation of their magnetization.
Co-reporter:Sanjit Nayak, George E. Kostakis, Christopher E. Anson and Annie K. Powell
CrystEngComm 2010 vol. 12(Issue 10) pp:3008-3011
Publication Date(Web):02 Jun 2010
DOI:10.1039/C002284E
Three compounds with analogous molecular formulae [Ln2(PhCO2)6(MeOH)4] were synthesized but the dimensionality of the structures depends on the ionic radius of the lanthanide centre.
Co-reporter:Valeriu Mereacre, Muhammad Nadeem Akhtar, Yanhua Lan, Ayuk M. Ako, Rodolphe Clérac, Christopher E. Anson and Annie K. Powell
Dalton Transactions 2010 vol. 39(Issue 20) pp:4918-4927
Publication Date(Web):19 Apr 2010
DOI:10.1039/B926899E
The structures and magnetic properties of a family of new octanuclear heterometallic 3d-4f complexes [MnIII4LnIII4(μ3-OH)4(μ2,η1-X)4(O2CBut)8(t-bdea)4]·solv, where X = N3−, Ln = Y (1), Eu (2), Gd (3), Tb (4), Dy (5), Ho (6); X = OCN−, Ln = Dy (7); X = NO3−, Ln = Gd (8), Tb (9), Dy (10), Ho (11), Er (12); solv = MeCN or toluene, are reported. The metal topology in the aggregates can be described as consisting of a “Ln4-square inscribed in a Mn4-square”. Complexes 1-7 are prepared by the reactions of t-butyldiethanolamine (t-bdeaH2) with a preformed hexanuclear manganese pivalate complex [Mn6], the respective lanthanide salt and either NaN3 or NaNCO, while 8-12 are obtained from the direct reaction of Mn(OAc)2, Ln(NO3)3·xH2O and t-butyldiethanolamine. The magnetic properties of all the complexes were investigated using variable temperature magnetic susceptibility and magnetisation measurements. Similar magnetic behaviour was observed for compounds containing the same lanthanide, indicating that changing the bridging ligand X does not have a significant effect on the magnetic behaviour. The TbIII and DyIII compounds 4, 5, 7, 9 and 10 all show frequency-dependent ac susceptibilities indicative of a slow relaxation of magnetisation and are therefore considered as Single-Molecule Magnets.
Co-reporter:Xiao-Qing Zhao, Yanhua Lan, Bin Zhao, Peng Cheng, Christopher E. Anson and Annie K. Powell
Dalton Transactions 2010 vol. 39(Issue 20) pp:4911-4917
Publication Date(Web):17 Apr 2010
DOI:10.1039/C002841J
The reaction of 2,6-pyridinedimethanol (pdmH2), CoCl2·6H2O, Ln(NO3)3·6H2O and pivalic acid (pivH) in the presence of triethylamine in MeCN and CH2Cl2 under ambient conditions results in the tetranuclear heterobimetallic compounds [CoII2Ln2(pdmH)4(Piv)6]·4CH3CN (Ln = Y (1), Gd (2), Tb (3), Ho (4)) and [CoII2Dy2(pdmH)4(Piv)6]·2CH3CN (5). The molecular structures of 1–5 were determined by single-crystal X-ray diffraction and reveal that they are isostructural. However, compounds 1–4 crystallize in the monoclinic space group P21/n, while compound 5 crystallizes in the orthorhombic space group Pnna. In all of these compounds, the four metal ions are held together by four alkoxide μ3-RCH2O− bridges to form novel Co2Ln2O4-heterocubanes. Magnetic properties of 1–5 have been investigated using dc and ac susceptibility measurements. Of these compounds, only compound 5 displays an out-of-phase signal in the ac susceptibility and exhibits slow relaxation of the magnetization, which is attributed to the presence of the anisotropic DyIII ions.
Co-reporter:Zeeshan Majeed, Kartik C. Mondal, George E. Kostakis, Yanhua Lan, Christopher E. Anson and Annie K. Powell
Dalton Transactions 2010 vol. 39(Issue 20) pp:4740-4743
Publication Date(Web):12 Feb 2010
DOI:10.1039/C000082E
Using glycerol (H3gly) as a primary ligand, the decanuclear aggregate [MnII2MnIII2DyIII6(μ3-OH)2(Hgly)4(H2gly)2(PhCO2)16(H2O)2]·10CH3CN (1) has been synthesised; it has a structure built up from two Mn2Dy2 heterocubane units linked through a central Dy2(μ-benzoate)4 paddle-wheel dimer and shows slow relaxation of its magnetisation.
Co-reporter:Hua Xiang, Yanhua Lan, Huan-Yong Li, Long Jiang, Tong-Bu Lu, Christopher E. Anson and Annie K. Powell
Dalton Transactions 2010 vol. 39(Issue 20) pp:4737-4739
Publication Date(Web):02 Mar 2010
DOI:10.1039/C000008F
Isostructural CoII2CoIII4LnIII4 (Ln = Y (1), Gd (2) and Dy (3)) coordination clusters formed using the ligand Tris are the first examples of 3d-4f complexes involving this ligand and show weak ferromagnetic coupling between the CoII ions and slow relaxation (SMM) behaviour for 3.
Co-reporter:Mengyuan Li, Ayuk M. Ako, Yanhua Lan, Wolfgang Wernsdorfer, Gernot Buth, Christopher E. Anson, Annie K. Powell, Zheming Wang and Song Gao
Dalton Transactions 2010 vol. 39(Issue 14) pp:3375-3377
Publication Date(Web):26 Feb 2010
DOI:10.1039/C000854K
Two heteroctanuclear wheel complexes with an eight-membered saddle-like ring of [MnIII4LnIII4] (Ln = Dy, Gd), prepared by employing formates as key carboxylate bridges, exhibit antiferromagnetic interactions between MnIII and LnIII centers, and the wheel containing anisotropic DyIII ions shows SMM behaviour.
Co-reporter:Ahmed Z. Eltayeb, Hassan I. Nimir, David A. Brown, Yanhua Lan, Christopher E. Anson, Annie K. Powell
Inorganica Chimica Acta 2010 Volume 363(Issue 5) pp:899-904
Publication Date(Web):22 March 2010
DOI:10.1016/j.ica.2009.12.043
The dinickel(II) compound [Ni2(μ-OAc)2(OAc)2(μ-H2O)(asy·dmen)2]·2.5H2O, 1; undergoes facile reaction in a 1:2 molar ratio with benzohydroxamic acid (BHA) in ethanol to give the novel nickel(II) tetranuclear hydroxamate complex [Ni4(μ-OAc)3(μ-BA)3(asy·dmen)3][OTf]2·H2O, 2, in which the bridging acetates, bridging two nickel atoms in 1, undergo a carboxylate shift from the μ2-η1:η1 bridging mode of binding to the μ3-η1:η2 bridging three nickel atoms in the tetramer. The structure of complex 2 was determined by single-crystal X-ray crystallography. The two monodentate acetates, water and two bidentate bridging acetates of two moles of complex 1 are replaced by three monodentate bridging acetates and three benzohydroxamates. Three nickel atoms in the tetramer, Ni(2), Ni(3) and Ni(4) are in a N2O4 octahedral environment, while the fourth nickel atom Ni(1) is in an O(6) octahedral environment. The Ni–Ni separations are Ni(1)–Ni(2) = 3.108 Å, Ni(1)–Ni(3) = 3.104 Å and Ni(1)–Ni(4) = 3.110 Å, which are longer than previously studied in dinuclear urease inhibited models but shorter than in the nickel(II) tetrameric glutarohydroxamate complex [Ni4(μ-OAc)2(μ-gluA2)2(tmen)4][OTf]2, isolated and characterized previously in this laboratory. Magnetic studies of the tetrameric complex show that the four Ni(II) ions are ferromagnetically coupled, leading to a total ground spin state ST = 4. Three analogous tetranuclear nickel hydroxamates were prepared from AHA and BHA and the appropriate dinuclear complex with either sy·dmen or asy·dmen as capping ligands.The reaction of the urease model complex 1, [Ni2(μ-OAc)2(OAc)2(μ-H2O)(asy·dmen)2]·2.5H2O, with benzohydroxamic acid (BHA) gives the novel nickel(II) tetranuclear hydroxamate complex [Ni4(μ-OAc)3(μ-BA)3(asy·dmen)3][OTf·H2O], 2, in which the bridging acetates undergo a carboxylate shift. Magnetic studies of the tetrameric complex show that the four Ni(II) ions are ferromagnetically coupled, leading to a total ground spin state ST = 4.
Co-reporter:Dirk Schray;Ghulam Abbas Dr.;Yanhua Lan Dr.;Valeriu Mereacre Dr.;Alexer Sundt;Jan Dreiser Dr.;Oliver Waldmann ;GeorgeE. Kostakis Dr.;ChristopherE. Anson Dr.;AnnieK. Powell Dr.
Angewandte Chemie 2010 Volume 122( Issue 30) pp:5312-5315
Publication Date(Web):
DOI:10.1002/ange.201001110
Co-reporter:IanJ. Hewitt Dr.;Jinkui Tang Dr.;N.T. Madhu Dr.;ChristopherE. Anson Dr.;Yanhua Lan Dr.;Javier Luzon Dr.;Mael Etienne;Roberta Sessoli ;AnnieK. Powell Dr.
Angewandte Chemie 2010 Volume 122( Issue 36) pp:6496-6500
Publication Date(Web):
DOI:10.1002/ange.201002691
Co-reporter:Dirk Schray;Ghulam Abbas Dr.;Yanhua Lan Dr.;Valeriu Mereacre Dr.;Alexer Sundt;Jan Dreiser Dr.;Oliver Waldmann ;GeorgeE. Kostakis Dr.;ChristopherE. Anson Dr.;AnnieK. Powell Dr.
Angewandte Chemie International Edition 2010 Volume 49( Issue 30) pp:5185-5188
Publication Date(Web):
DOI:10.1002/anie.201001110
Co-reporter:IanJ. Hewitt Dr.;Jinkui Tang Dr.;N.T. Madhu Dr.;ChristopherE. Anson Dr.;Yanhua Lan Dr.;Javier Luzon Dr.;Mael Etienne;Roberta Sessoli ;AnnieK. Powell Dr.
Angewandte Chemie International Edition 2010 Volume 49( Issue 36) pp:6352-6356
Publication Date(Web):
DOI:10.1002/anie.201002691
Co-reporter:Julia Rinck;Dr. Ghenadie Novitchi;Willem VandenHeuvel;Liviu Ungur;Dr. Yanhua Lan;Dr. Wolfgang Wernsdorfer;Dr. Christopher E. Anson;Dr. Liviu F. Chibotaru;Dr. Annie K. Powell
Angewandte Chemie International Edition 2010 Volume 49( Issue 41) pp:7583-7587
Publication Date(Web):
DOI:10.1002/anie.201002690
Co-reporter:Julia Rinck;Dr. Ghenadie Novitchi;Willem VandenHeuvel;Liviu Ungur;Dr. Yanhua Lan;Dr. Wolfgang Wernsdorfer;Dr. Christopher E. Anson;Dr. Liviu F. Chibotaru;Dr. Annie K. Powell
Angewandte Chemie 2010 Volume 122( Issue 41) pp:7746-7750
Publication Date(Web):
DOI:10.1002/ange.201002690
Co-reporter:Hua Xiang, Yanhua Lan, Huan-Yong Li, Long Jiang, Tong-Bu Lu, Christopher E. Anson and Annie K. Powell
Dalton Transactions 2010 - vol. 39(Issue 20) pp:NaN4739-4739
Publication Date(Web):2010/03/02
DOI:10.1039/C000008F
Isostructural CoII2CoIII4LnIII4 (Ln = Y (1), Gd (2) and Dy (3)) coordination clusters formed using the ligand Tris are the first examples of 3d-4f complexes involving this ligand and show weak ferromagnetic coupling between the CoII ions and slow relaxation (SMM) behaviour for 3.
Co-reporter:Sebastian Schmidt, Denis Prodius, Valeriu Mereacre, George E. Kostakis and Annie K. Powell
Chemical Communications 2013 - vol. 49(Issue 17) pp:NaN1698-1698
Publication Date(Web):2012/12/06
DOI:10.1039/C2CC38006D
A nonanuclear {Fe6Dy3} coordination cluster displaying SMM behaviour in which an unprecedented chemical transformation provides structural information for the existence of 1,1,2,2-tetrahydroxyethane is reported.
Co-reporter:Humphrey L. C. Feltham, Sébastien Dhers, Mathieu Rouzières, Rodolphe Clérac, Annie K. Powell and Sally Brooker
Inorganic Chemistry Frontiers 2015 - vol. 2(Issue 11) pp:NaN990-990
Publication Date(Web):2015/09/07
DOI:10.1039/C5QI00130G
A family of fourteen tetranuclear, 3d–4f heterometallic nickel(II)–lanthanide(III) complexes of the hexaimine macrocycle (LPr)6−, with general formula NiII3LnIII(LPr)(NO3)3·xsolvents (LnIII = LaIII, CeIII, PrIII, NdIII, SmIII, EuIII, GdIII, TbIII, DyIII, HoIII, ErIII, TmIII, YbIII or LuIII), were prepared in a one-pot synthesis using a 3:1:3:3 reaction of nickel(II) acetate, the appropriate lanthanide(III) nitrate, the dialdehyde 1,4-diformyl-2,3-dihydroxybenzene (H2LAld) and 1,3-diaminopropane. In addition, three tetranuclear heterometallic nickel(II)–lanthanide(III) complexes of H2LAld, with general formula NiII3LnIII(LAld)3(NO3)3·xsolvents, were deliberately prepared (LnIII = LaIII, DyIII or YbIII) as in effect they represent intermediates en route to the above macrocyclic complexes. Whilst single crystals of the macrocyclic complexes were not forthcoming, X-ray crystal structure determinations on NiII3LnIII(LAld)3(NO3)3·xsolvents (LnIII = DyIII or YbIII) confirmed that the large ten-coordinate lanthanide(III) ion is bound in the central O6 pocket while the smaller six-coordinate nickel(II) ions are bound in the outer O4 pockets. In all fourteen cases, addition of the diamine to this intermediate (all in one pot) gives the tetrametallic [3 + 3] macrocyclic product. The magnetic properties of all fourteen macrocyclic complexes were measured down to 1.8 K to check for Single-Molecule Magnet behaviour, but no slow dynamics of magnetisation was observed.
Co-reporter:Sihuai Chen, Valeriu Mereacre, George E. Kostakis, Christopher E. Anson and Annie K. Powell
Inorganic Chemistry Frontiers 2017 - vol. 4(Issue 6) pp:NaN934-934
Publication Date(Web):2017/03/28
DOI:10.1039/C7QI00091J
Four isostructural MIII4LnIII2 coordination clusters, [M4Ln2(μ3-OH)2(nbdea)4(C6H5COO)8]·MeCN (M = Fe, Ln = Er (1); M = Ga, Ln = Er (2); M = Fe, Ln = Ho (3); M = Ga, Ln = Ho (4)) have been synthesized and characterized. Single-crystal X-ray diffraction and X-ray powder diffraction studies revealed that all four compounds crystallize isomorphously to each other, and to the previously reported MIII4DyIII2 (M = Fe or Ga) and FeIII4YIII2 analogues. DC magnetic susceptibility measurements for compounds 1–4, taken in combination with those for the FeIII4YIII2 analogue, indicated that the interactions between ErIII ions are weakly ferromagnetic and the FeIII–ErIII interactions are very weakly antiferromagnetic, while the HoIII–HoIII and FeIII–HoIII interactions are both negligible. By comparison, for the FeIII4DyIII2 analogue, the DyIII–DyIII interactions are antiferromagnetic while the FeIII–DyIII are ferromagnetic. Both Er analogues 1 and 2 display single-molecule magnet (SMM) behavior with the effective energy barrier Ueff increasing from 12.8 K (for Fe4Er21) to 53.5 K (for Ga4Er22), indicating that the very weak 3d–4f interaction enhances the QTM effect.
Co-reporter:Nicolas Leblanc, Damiano Genovese, Luisa De Cola and Annie K. Powell
Physical Chemistry Chemical Physics 2017 - vol. 19(Issue 10) pp:NaN6988-6988
Publication Date(Web):2016/11/30
DOI:10.1039/C6CP07538J
The N,N′-dimethyl-3,3′-biquinoxalinium “methylbiquinoxen” dicationic platform is revealed to have even more fascinating possibilities than we originally thought in terms of its chemical versatility. In addition to its rich redox chemistry and coordination abilities, we have now unveiled an unexpected Lewis acid/base chemistry linked with a tuneable switching of its luminescence properties. This, amongst other things, allows for the facile fluorescent covalent labelling of hydroxyl-terminated materials. This platform provides intriguing chemical prospects realised in molecular systems such as porphyrins as well as an easy alternative functionalisation methodology to that provided by click-chemistry.
Co-reporter:Yan Peng, Valeriu Mereacre, Christopher E. Anson and Annie K. Powell
Dalton Transactions 2017 - vol. 46(Issue 16) pp:NaN5343-5343
Publication Date(Web):2017/03/14
DOI:10.1039/C7DT00548B
Three defect-dicubane coordination clusters related to our previously reported butterfly compound, [Co2Dy2(L)4(NO3)2(THF)2]·4THF (1) and formulated as [Co2Dy2(L)4(NO3)2(MeOH)2]·2CH2Cl2 (2), [Co2Dy2(L)4(NO3)2(DMF)2]·2C2H6CO (3) and [Zn2Dy2(L)4(NO3)2(MeOH)2]·2CH2Cl2 (4) were synthesised and characterised. All show typical SMM behaviour which is steered through the nature of the solvent molecule coordinated to the central 3d ions. The ZnII2DyIII2, (4) provides experimental proof of the suggestion that in such CoII2DyIII2 compounds two major relaxation pathways can be important in determining the overall magnetic behaviour of CoII-4f systems.
Co-reporter:Denis Prodius, Fliur Macaev, Eugenia Stingaci, Vsevolod Pogrebnoi, Valeriu Mereacre, Ghenadie Novitchi, George E. Kostakis, Christopher E. Anson and Annie K. Powell
Chemical Communications 2013 - vol. 49(Issue 19) pp:NaN1917-1917
Publication Date(Web):2012/10/22
DOI:10.1039/C2CC36741F
A new class of task-specific ionic liquids (ILs) which contain septuply positively charged {Fe3IIIO(RCOO)6L3}7+ triangles has been synthesized and structurally characterized. Such metal-containing ILs can be repeatedly used as alternative catalysts in the synthesis of 2-pyrrolo-3′-yloxindole or the condensation of indoles with various aldehydes.
Co-reporter:Irina A. Kühne, George E. Kostakis, Christopher E. Anson and Annie K. Powell
Chemical Communications 2015 - vol. 51(Issue 13) pp:NaN2705-2705
Publication Date(Web):2015/01/02
DOI:10.1039/C4CC09469G
[CuII27(μ4-O)2(OH)13(OMe)7(vanox)10(NO3)8(OH2)2(MeOH)7](NO3)2·2H2O·11MeOH (1) was synthesised from Cu(NO3)2·3H2O and o-vanillin-oxime. Structural analysis shows a molecule composed of a Cu18 “folded-sheet” motif linked to a Cu9 bridging unit. The cluster is highly frustrated and has an S = 1/2 spin ground state.
Co-reporter:Nicolas Leblanc, Stephen Sproules, Claude Pasquier, Pascale Auban-Senzier, Helene Raffy and Annie K. Powell
Chemical Communications 2015 - vol. 51(Issue 64) pp:NaN12743-12743
Publication Date(Web):2015/06/18
DOI:10.1039/C5CC04142B
A novel 1D hybrid salt (MQ)[CuBr2]∞ (MQ = N-methylquinoxalinium) is reported. Structural, spectroscopic and magnetic investigations reveal a minimal CuII doping of less than 0.1%. However it is not possible to distinguish CuI and CuII. The unusually close packing of the organic moieties and the dark brown colour of the crystals suggest a defect electronic structure.
Co-reporter:Irina A. Kühne, Nicola Magnani, Valeriu Mereacre, Wolfgang Wernsdorfer, Christopher E. Anson and Annie K. Powell
Chemical Communications 2014 - vol. 50(Issue 15) pp:NaN1885-1885
Publication Date(Web):2013/11/21
DOI:10.1039/C3CC46458J
The structure and magnetic properties of an octanuclear coordination cluster with a {CuII4DyIII4} core are described and a model for the unusual SMM behaviour is proposed.
Co-reporter:Denis Prodius, Fliur Macaev, Yanhua Lan, Ghenadie Novitchi, Serghei Pogrebnoi, Eugenia Stingaci, Valeriu Mereacre, Christopher E. Anson and Annie K. Powell
Chemical Communications 2013 - vol. 49(Issue 80) pp:NaN9217-9217
Publication Date(Web):2013/08/07
DOI:10.1039/C3CC45554H
Dysprosium based ionic liquids displaying slow relaxation of magnetization at low temperatures are reported.
Co-reporter:Zeeshan Majeed, Kartik C. Mondal, George E. Kostakis, Yanhua Lan, Christopher E. Anson and Annie K. Powell
Chemical Communications 2010 - vol. 46(Issue 15) pp:NaN2553-2553
Publication Date(Web):2010/02/24
DOI:10.1039/B923998G
We present the surprising result that the combination of the monotopic benzoate ligand with lanthanide ions leads to a 3D network which also possesses the chiral srs-topology.
Co-reporter:Sihuai Chen, Valeriu Mereacre, Christopher E. Anson and Annie K. Powell
Dalton Transactions 2016 - vol. 45(Issue 1) pp:NaN106-106
Publication Date(Web):2015/11/04
DOI:10.1039/C5DT03909F
Two series of heterometallic FeIII–LnIII compounds, [FeIII4LnIII2(μ3-OH)2(mdea)4(m-NO2C6H4COO)8]·3MeCN where Ln = Y (1) and Dy (2) and [FeIII6LnIII3(μ4-O)3(μ3-O)(mdea)5(m-NO2C6H4COO)9]·3MeCN where Ln = Y (3) and Dy (4), were synthesized. Compounds 1 and 2 were obtained under ambient conditions, whereas 3 and 4 were obtained via a solvothermal transformation process by heating 1 or 2 at 120 °C in MeCN. The magnetic properties of all four compounds have been measured and show that compounds 2 and 4 containing DyIII ions exhibit slow relaxation of magnetization characteristic of Single Molecule Magnetic (SMM) behaviour.
Co-reporter:Nikolaos C. Anastasiadis, Christina D. Polyzou, George E. Kostakis, Vlasoula Bekiari, Yanhua Lan, Spyros P. Perlepes, Konstantis F. Konidaris and Annie K. Powell
Dalton Transactions 2015 - vol. 44(Issue 46) pp:NaN19795-19795
Publication Date(Web):2015/10/14
DOI:10.1039/C5DT03663A
The first use of methyl 2-pyridyl ketone oxime (mpkoH) in zinc(II)/lanthanide(III) chemistry leads to the [ZnLn(mpko)3(mpkoH)3](ClO4)2 and [ZnLn(NO3)2(mpko)3(mpkoH)] families of dinuclear ZnIILnIII complexes displaying blue-green, ligand-based photoluminescence; the ZnIIDyIII compound shows field-induced relaxation of magnetization.
Co-reporter:Noelia M. Sanchez-Ballester, Lok Kumar Shrestha, Mark R. J. Elsegood, Wolfgang Schmitt, Katsuhiko Ariga, Christopher E. Anson, Jonathan P. Hill and Annie K. Powell
Dalton Transactions 2013 - vol. 42(Issue 8) pp:NaN2785-2785
Publication Date(Web):2012/12/04
DOI:10.1039/C2DT32547K
A dinuclear manganese(III) complex (1) of an N-(carboxymethyl)-N-[3,5-bis(α,α-dimethylbenzyl-2-hydroxybenzyl)]glycine (HDA) ligand (L) binds a manganese(II) species through displacement of its solvating ligands by appropriately dispositioned carbonyl groups of a dinuclear complex {[Mn2(L)2(OH)(OCH3)][Mn(H2O)3(CH3OH)3], 2, triclinic P, a = 13.172(3) Å, b = 15.897(3) Å, c = 19.059(4) Å, V = 3461.9(13) Å3} leading to a trinuclear complex {3, monoclinic P21/n, a = 11.7606(8) Å, b = 21.3505(8) Å, c = 26.7827(17) Å, V = 6722.7(7) Å3} with cyclization of two of the carboxy groups through the doubly-carboxy group coordinated Mn2+ ion. The reaction is discussed in terms of its significance as an illustration of how Mn2+ ions might be sequestered in biological systems. A similar solvato-ligand displacement reaction was used to synthesise coordination polymers of an HDA iron(III) complex involving polymerization through a bridging carboxylato group. Several isostructural polymers (5–7; for 5: orthorhombic Pbca, a = 9.411(5) Å, b = 16.390(8) Å, c = 37.968(19) Å, V = 5856(5) Å3) with different coordinated alcohols could be prepared indicating the potential synthetic uses of this method.
Co-reporter:Franziska Völcker, Yanhua Lan, Annie K. Powell and Peter W. Roesky
Dalton Transactions 2013 - vol. 42(Issue 32) pp:NaN11475-11475
Publication Date(Web):2013/07/05
DOI:10.1039/C3DT51078F
Two homoleptic phosphanylamido dysprosium complexes [Li(THF)4][(Ph2PNPh)4Dy] and [Dy{N(PPh2)2}3] have been synthesized. Both have a highly symmetric arrangement of the ligand which is only slightly broken in the solid state by steric and packing effects as a result of the weak coordination of phosphorus atoms to the metal centre. Magnetic properties of these two compounds are similar with both showing slow magnetic relaxation.
Co-reporter:Dominique T. Thielemann, Anna T. Wagner, Yanhua Lan, Christopher E. Anson, Michael T. Gamer, Annie K. Powell and Peter W. Roesky
Dalton Transactions 2013 - vol. 42(Issue 41) pp:NaN14800-14800
Publication Date(Web):2013/08/29
DOI:10.1039/C3DT50133G
The synthesis and characterization of three chiral and one achiral amino acid anion ligated dysprosium hydroxo clusters [Dy5(OH)5(α-AA)4(Ph2acac)6] (α-AA = D-PhGly, L-Pro, L-Trp, Ph2Gly; Ph2acac = dibenzoylmethanide) are reported. The solid state structures were determined using single crystal X-ray diffraction and show that five Dy(III) ions are arranged in a square-based pyramidal geometry with NO7-donor-sets for the basal and O8-donor-sets for the apical Dy atom. Both static (dc) and dynamic (ac) magnetic properties were investigated for all four compounds and show a slow relaxation of magnetization, indicative of single molecule magnet (SMM) behaviour below 10 K in all cases. The similar SMM behaviour observed for all four compounds suggests that the very similar coordination geometries seen for the dysprosium atoms in all members of this family, which are independent of the amino acid ligand used, play a decisive role in steering the contribution of the single ion anisotropies to the observed magnetic relaxation.
Co-reporter:Xiao-Qing Zhao, Yanhua Lan, Bin Zhao, Peng Cheng, Christopher E. Anson and Annie K. Powell
Dalton Transactions 2010 - vol. 39(Issue 20) pp:NaN4917-4917
Publication Date(Web):2010/04/17
DOI:10.1039/C002841J
The reaction of 2,6-pyridinedimethanol (pdmH2), CoCl2·6H2O, Ln(NO3)3·6H2O and pivalic acid (pivH) in the presence of triethylamine in MeCN and CH2Cl2 under ambient conditions results in the tetranuclear heterobimetallic compounds [CoII2Ln2(pdmH)4(Piv)6]·4CH3CN (Ln = Y (1), Gd (2), Tb (3), Ho (4)) and [CoII2Dy2(pdmH)4(Piv)6]·2CH3CN (5). The molecular structures of 1–5 were determined by single-crystal X-ray diffraction and reveal that they are isostructural. However, compounds 1–4 crystallize in the monoclinic space group P21/n, while compound 5 crystallizes in the orthorhombic space group Pnna. In all of these compounds, the four metal ions are held together by four alkoxide μ3-RCH2O− bridges to form novel Co2Ln2O4-heterocubanes. Magnetic properties of 1–5 have been investigated using dc and ac susceptibility measurements. Of these compounds, only compound 5 displays an out-of-phase signal in the ac susceptibility and exhibits slow relaxation of the magnetization, which is attributed to the presence of the anisotropic DyIII ions.
Co-reporter:Valeriu Mereacre, Muhammad Nadeem Akhtar, Yanhua Lan, Ayuk M. Ako, Rodolphe Clérac, Christopher E. Anson and Annie K. Powell
Dalton Transactions 2010 - vol. 39(Issue 20) pp:NaN4927-4927
Publication Date(Web):2010/04/19
DOI:10.1039/B926899E
The structures and magnetic properties of a family of new octanuclear heterometallic 3d-4f complexes [MnIII4LnIII4(μ3-OH)4(μ2,η1-X)4(O2CBut)8(t-bdea)4]·solv, where X = N3−, Ln = Y (1), Eu (2), Gd (3), Tb (4), Dy (5), Ho (6); X = OCN−, Ln = Dy (7); X = NO3−, Ln = Gd (8), Tb (9), Dy (10), Ho (11), Er (12); solv = MeCN or toluene, are reported. The metal topology in the aggregates can be described as consisting of a “Ln4-square inscribed in a Mn4-square”. Complexes 1-7 are prepared by the reactions of t-butyldiethanolamine (t-bdeaH2) with a preformed hexanuclear manganese pivalate complex [Mn6], the respective lanthanide salt and either NaN3 or NaNCO, while 8-12 are obtained from the direct reaction of Mn(OAc)2, Ln(NO3)3·xH2O and t-butyldiethanolamine. The magnetic properties of all the complexes were investigated using variable temperature magnetic susceptibility and magnetisation measurements. Similar magnetic behaviour was observed for compounds containing the same lanthanide, indicating that changing the bridging ligand X does not have a significant effect on the magnetic behaviour. The TbIII and DyIII compounds 4, 5, 7, 9 and 10 all show frequency-dependent ac susceptibilities indicative of a slow relaxation of magnetisation and are therefore considered as Single-Molecule Magnets.
Co-reporter:Yan Peng, Valeriu Mereacre, Christopher E. Anson and Annie K. Powell
Physical Chemistry Chemical Physics 2016 - vol. 18(Issue 31) pp:NaN21480-21480
Publication Date(Web):2016/07/05
DOI:10.1039/C6CP02942F
A [DyFeIII2Dy(μ3-OH)2(pmide)2(p-Me-PhCO2)6] coordination cluster, where pmideH2 = N-(2-pyridylmethyl)iminodiethanol, has been synthesized and the magnetic properties studied. The dc magnetic measurements reveal dominant antiferromagnetic interactions between the metal centres. The ac measurements reveal zero-field quantum tunnelling of the magnetisation (QTM) which can be understood, but not adequately modelled, in terms of at least three relaxation processes when appropriate static (dc) fields are applied. To investigate this further, 57Fe Mössbauer spectroscopy was used and well-resolved nuclear hyperfine structures could be observed, showing that on the Mössbauer time scale, without applied field or else with very small applied fields, the iron nuclei experience three or more superhyperfine fields arising from the slow magnetisation reversal of the strongly polarized fields of the DyIII ions.
Co-reporter:Zeeshan Majeed, Kartik C. Mondal, George E. Kostakis, Yanhua Lan, Christopher E. Anson and Annie K. Powell
Dalton Transactions 2010 - vol. 39(Issue 20) pp:NaN4743-4743
Publication Date(Web):2010/02/12
DOI:10.1039/C000082E
Using glycerol (H3gly) as a primary ligand, the decanuclear aggregate [MnII2MnIII2DyIII6(μ3-OH)2(Hgly)4(H2gly)2(PhCO2)16(H2O)2]·10CH3CN (1) has been synthesised; it has a structure built up from two Mn2Dy2 heterocubane units linked through a central Dy2(μ-benzoate)4 paddle-wheel dimer and shows slow relaxation of its magnetisation.
Co-reporter:Mengyuan Li, Ayuk M. Ako, Yanhua Lan, Wolfgang Wernsdorfer, Gernot Buth, Christopher E. Anson, Annie K. Powell, Zheming Wang and Song Gao
Dalton Transactions 2010 - vol. 39(Issue 14) pp:NaN3377-3377
Publication Date(Web):2010/02/26
DOI:10.1039/C000854K
Two heteroctanuclear wheel complexes with an eight-membered saddle-like ring of [MnIII4LnIII4] (Ln = Dy, Gd), prepared by employing formates as key carboxylate bridges, exhibit antiferromagnetic interactions between MnIII and LnIII centers, and the wheel containing anisotropic DyIII ions shows SMM behaviour.
Co-reporter:Zeeshan Majeed, George E. Kostakis, Yanhua Lan and Annie K. Powell
Dalton Transactions 2011 - vol. 40(Issue 45) pp:NaN12216-12216
Publication Date(Web):2011/09/06
DOI:10.1039/C1DT10917K
We report herein five new coordination polymers of general formula [LnNa(C6H5CO2)4] where Ln = Y (6), Tb (7), Er (8), [DyNa(CH3CO2)4(MeOH)] (9) and [DyNa(C3H7CO2)4] (10). Single crystal structure analyses revealed that all compounds have a repeating unit containing one Ln3+, one Na+ and four monocarboxylate ligands (RCO2−) (R = –CH3, –C3H7, –C6H5). Compounds 6–8 and 10 possess helical polymeric structures which are extended in three dimensions forming chiral srs networks whilst compound 9 constitutes a two dimensional honeycomb network, illustrating that variation in the alkyl group of the monocarboxylate can result in versatile and variable polymeric networks. The magnetic properties of the reported compounds have also been studied.
Co-reporter:Humphrey L. C. Feltham, Frederik Klöwer, Scott A. Cameron, David S. Larsen, Yanhua Lan, Manuel Tropiano, Stephen Faulkner, Annie K. Powell and Sally Brooker
Dalton Transactions 2011 - vol. 40(Issue 43) pp:NaN11432-11432
Publication Date(Web):2011/09/21
DOI:10.1039/C1DT11038A
A family of thirteen tetranuclear heterometallic zinc(II)-lanthanide(III) complexes of the hexa-imine macrocycle (LPr)6−, with general formula ZnII3LnIII(LPr)(NO3)3·xsolvents (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm or Yb), were prepared in a one-pot synthesis using a 3:1:3:3 reaction of zinc(II) acetate, the appropriate lanthanide(III) nitrate, the dialdehyde 1,4-diformyl-2,3-dihydroxybenzene (H2L1) and 1,3-diaminopropane. A hexanuclear homometallic zinc(II) macrocyclic complex [Zn6(LPr)(OAc)5(OH)(H2O)]·3H2O was obtained using a 2:0:1:1 ratio of the same reagents. A control experiment using a 1:0:1:1 ratio failed to generate the lanthanide-free [Zn3(LPr)] macrocyclic complex. The reaction of H2L1 and zinc(II) acetate in a 1:1 ratio yielded the pentanuclear homometallic complex of the dialdehyde H2L1, [Zn5(L1)5(H2O)6]·3H2O. An X-ray crystal structure determination revealed [Zn3IIPrIII(LPr)(NO3)2(DMF)3](NO3)·0.9DMF has the large ten-coordinate lanthanide(III) ion bound in the central O6 site with two bidentate nitrate anions completing the O10 coordination sphere. The three square pyramidal zinc(II) ions are in the outer N2O2 sites with a fifth donor from DMF. Measurement of the magnetic properties of [ZnII3DyIII(LPr)(NO3)3(MeOH)3]·4H2O with a weak external dc field showed that it has a frequency-dependent out-of-phase component of ac susceptibility, indicative of slow relaxation of the magnetization (SMM behaviour). Likewise, the Er and Yb analogues are field-induced SMMs; the latter is only the second example of a Yb-based SMM. The neodymium, ytterbium and erbium complexes are luminescent in the solid phase, but only the ytterbium and neodymium complexes show strong lanthanide-centred luminescence in DMF solution.
Co-reporter:Amer Baniodeh, Ian J. Hewitt, Valeriu Mereacre, Yanhua Lan, Ghenadie Novitchi, Christopher E. Anson and Annie K. Powell
Dalton Transactions 2011 - vol. 40(Issue 16) pp:NaN4086-4086
Publication Date(Web):2011/03/09
DOI:10.1039/C0DT01742F
The reaction of triethanolamine (teaH3) with [FeIII3O(O2CCH3)6(H2O)3]Cl·6H2O and Ln(NO3)3·6H2O in acetonitrile yields [Fe16Ln4(tea)8(teaH)12(μ-O2CCH3)8](NO3)4·16H2O·xMeCN (Ln = Sm (1), Eu (2), Gd (3), Tb (4), Dy (5), Ho (6); x = 10 or 11). These 20-membered metallo-ring complexes are the largest such single-stranded oxygen-bridged rings so far reported. The structure is stabilised by two of the acetate ligands, which form anti,anti-bridges across the centre of the ring, pinching the ring and giving it rigidity. The magnetic properties are dominated by the antiferromagnetic couplings between the FeIII centres. Although the Fe2 and Fe6 sub-chains within the ring are fully spin-compensated at low temperatures with Ssubchain = 0, coupling between the GdIII cations and the FeIII centres at the ends of the sub-chains (in 3) results in a pinning of the lanthanide spins. The 57Fe Mössbauer spectra of 3 and 5 obtained at low temperatures are consistent with the presence of FeIII intracluster strong antiferromagnetic coupling. The applied field spectrum for 3 reveals no magnetic hyperfine interaction apart from that of the nucleus with the applied field, while the one for 5 is a superposition of three subspectra which show contributions from each of the peripheral as well as from the central iron sites.
Co-reporter:Amer Baniodeh, Yanhua Lan, Ghenadie Novitchi, Valeriu Mereacre, Andrey Sukhanov, Marilena Ferbinteanu, Violeta Voronkova, Christopher E. Anson and Annie K. Powell
Dalton Transactions 2013 - vol. 42(Issue 24) pp:NaN8938-8938
Publication Date(Web):2013/03/28
DOI:10.1039/C3DT00105A
The reaction of [Fe3O(O2CPh)6(H2O)3](O2CPh) with lanthanide/rare earth nitrate salts in the presence of triethanolamine (H3tea) in acetonitrile/methanol solution yields a series of compounds with isostructural tetranuclear core motifs [FeIII2LnIII2(μ3-OH)2(teaH)2(O2CCPh)6]·3MeCN (Ln = Ce (1), Pr (2), Nd (3), Sm (4), Eu (5), Gd (6), Tb (7), Dy (8), Ho (9), Er (10), Tm (11), Yb (12), Y (13)). In all cases the core topology is a defect-dicubane planar or “butterfly” Fe2Ln2 motif. Compounds 1–13 were investigated using a combination of experimental techniques and theoretical studies. Magnetic susceptibility measurements were carried out on all compounds. The magnetic coupling between the two FeIII centres is antiferromagnetic, with JFeFeca. −6.71(4) cm−1, while the Fe–Ln couplings are much weaker, e.g. JFeGd = 0.18(1) cm−1. Compounds 6, 7, 8 and 13 were selected for Mössbauer studies in order to investigate the influence of isotropic (GdIII), highly anisotropic non-Kramers and Kramers (TbIII and DyIII) and diamagnetic (YIII) rare earth ions on the local environment of the FeIII centres. Compounds 3, 6, 8 and 13 were also studied using X-Band EPR spectroscopy. For 13, with the diamagnetic YIII ion, this made it possible to obtain the D, E, JFeFe and g parameters for the iron centres. It is shown that the low-temperature spectra of compounds 3, 6 and 8 are determined by magnetic properties of rare-earth ions and the dipole–dipole interactions between the LnIII ions. The Fe–Ln interactions were confirmed as very weak and dipolar in nature by the temperature dependence of EPR spectra at T > 20 K.
Co-reporter:Konstantin V. Shuvaev, Stephen Sproules, J. Mikko. Rautiainen, Eric J. L. McInnes, David Collison, Christopher E. Anson and Annie K. Powell
Dalton Transactions 2013 - vol. 42(Issue 7) pp:NaN2381-2381
Publication Date(Web):2012/09/11
DOI:10.1039/C2DT31946B
A novel multitopic, two-pocket ligand HLnitnitnitnit, containing the nitronyl nitroxide radical, has been designed for a self-assembled [2 × 2] grid system. HLnitnitnitnit is not stable in methanol and slowly undergoes a disproportionation, during which the nitronyl nitroxide radical converts to the diamagnetic amidino oxide. In situ reaction of HLnitnitnitnit with Cu(BF4)2 in methanol depending on the reaction time affords self-assembled [2 × 2] grids (Lnitnitnitnit)2(L)2Cu(II)4(BF4)4·CH3OH (1) or (Lnitnitnitnit)0.5(L)3.5Cu(II)4(BF4)4·CH3OH (2), in which L contains an amidino oxide arising from a 3-electron reduction of the nitronyl nitroxide radical. The percentages of stable radical in grids 1 and 2 as determined by X-ray are 50 and 12.5%, respectively. Structures 1 and 2 contain a six-coordinated distorted Cu(II) that is oxo-bridged at 140°. The nitronyl nitroxide radical coordinates via the oxo-atom of the N+–O− fragment in a chelating fashion and lies in the equatorial plane of the metal ion. The magnetic properties of 1 could be fitted to a 5-spin Hamiltonian with JCu–Cu = +3.1 cm−1 and JCu–Nit = −278 cm−1, while those of 2 to a 4-spin Hamiltonian with JCu–Cu = +2.9 cm−1. The Q-band EPR spectra of 1 and 2 recorded in solution at 20 K showed intricate anisotropic features of the Cu(II) ion and a much weaker signal of the –NO˙ fragment, associated with a strong Cu(II)–Nit antiferromagentic coupling. The DFT calculated (B3LYP/TZVP/6-31G*) magnetic coupling constants for the grid of 1 were JCu–Cu = +5 cm−1 and JCu–Nit = −282 cm−1, which are in very good agreement with the experimentally obtained values.
Co-reporter:Konstantis F. Konidaris, Christina D. Polyzou, George E. Kostakis, Anastasios J. Tasiopoulos, Olivier Roubeau, Simon J. Teat, Evy Manessi-Zoupa, Annie K. Powell and Spyros P. Perlepes
Dalton Transactions 2012 - vol. 41(Issue 10) pp:NaN2865-2865
Publication Date(Web):2011/11/28
DOI:10.1039/C1DT11881A
Metal-ion mediated reactions of 2-pyridinealdoxime and hexafluorophosphate lead to ZnII complexes containing picolinic acid, picolinamide and monofluorophosphate (−2) as ligands.
Co-reporter:Guo Peng, George E. Kostakis, Yanhua Lan and Annie K. Powell
Dalton Transactions 2013 - vol. 42(Issue 1) pp:NaN49-49
Publication Date(Web):2012/09/04
DOI:10.1039/C2DT32027D
The first use of triethylene glycol (H2teg) in Fe/Ln chemistry affords two series of tetranuclear {FeIII2LnIII2} coordination clusters possessing defect-dicubane cores. A change in the synthetic procedure results in a different arrangement of the relative positions of the 3d and 4f elements offering a means to steer the structural and electronic features within a 3d–4f system.
Co-reporter:Ayuk M. Ako, Yanhua Lan, Valeriu Mereacre, Eliseo Ruiz, Daniel Aravena, Christopher E. Anson and Annie K. Powell
Dalton Transactions 2013 - vol. 42(Issue 26) pp:NaN9612-9612
Publication Date(Web):2013/04/15
DOI:10.1039/C3DT50345C
The synthesis of the high-nuclearity FeIII14 coordination cluster [Fe14(μ3-O)6(μ3-OH)4(μ-OH)3Cl11(dea)4(Hdea)3]Cl·H2O·27MeCN (1) is reported (in which deaH2 = diethanolamine). X-ray crystallographic analysis revealed that compound 1 crystallises in the cubic space group Im with Z = 24 and 8 independent Fe centres. Unusually for an FeIII coordination cluster, the FeIII centres in 1 adopt a range of 4, 5 and 6 coordinate geometries. Complex 1 presents a ferracalixarene topology which can be described in terms of a “half tennis ball” structure and binds a chloride anion guest via multiple hydrogen bonds. The curvature in the structure induced by this topology affects the overall spin structure. A ground spin state of S = 7 is proposed using a combination of magnetic susceptibility data and density functional theory (DFT) calculations.
Co-reporter:Amer Baniodeh, Nicola Magnani, Stefan Bräse, Christopher E. Anson and Annie K. Powell
Dalton Transactions 2015 - vol. 44(Issue 14) pp:NaN6347-6347
Publication Date(Web):2015/03/02
DOI:10.1039/C5DT00237K
Two new examples of Dy6 cyclic coordination clusters have been synthesised in order to discover how the toroidal moment in such a motif can be tuned and optimised.
Co-reporter:Sihuai Chen, Valeriu Mereacre, Christopher E. Anson and Annie K. Powell
Dalton Transactions 2016 - vol. 45(Issue 22) pp:NaN9344-9344
Publication Date(Web):2016/05/10
DOI:10.1039/C6DT01364C
The compounds of the system [M4M′2(μ3-OH)2(nbdea)4(C6H5CO2)8]·MeCN, where M = GaIII, M′ = DyIII (2), M = FeIII, M′ = YIII (3) are isostructural to the known [Fe4Dy2] compound (1). Those of the system [M4M′4(μ3-OH)4(nbdea)4(m-CH3C6H4CO2)12]·nMeCN, where M = GaIII, M′ = DyIII, n = 4 (5), M = FeIII, M′ = YIII, n = 1 (6) are isostructural to the [Fe4Dy4] compound (4). This allows for comparisons between single ion effects of the paramagnetic ions. The structures were determined using single crystal analysis. Magnetic susceptibility measurements reveal that the GaIII–DyIII compounds 2 and 5 are SMMs. The energy barrier for 2 is close to that for the known isostructural Fe4Dy2 compound (1), but with a significantly increased relaxation time.
Co-reporter:Ghenadie Novitchi, Guillaume Pilet, Liviu Ungur, Victor V. Moshchalkov, Wolfgang Wernsdorfer, Liviu F. Chibotaru, Dominique Luneau and Annie K. Powell
Chemical Science (2010-Present) 2012 - vol. 3(Issue 4) pp:NaN1176-1176
Publication Date(Web):2012/01/30
DOI:10.1039/C2SC00728B
The first example of exchange coupling between the toroidal moments in chiral heterometallic CuII/DyIII 1D polymers built from alternating trinuclear Dy3 SMM-building blocks and chiral copper(II) complexes is reported. A very strong toroidal magnetization can be induced by applying a magnetic field at low temperature in single-crystals of these compounds.
Co-reporter:Amer Baniodeh, Christopher E. Anson and Annie K. Powell
Chemical Science (2010-Present) 2013 - vol. 4(Issue 12) pp:NaN4361-4361
Publication Date(Web):2013/08/29
DOI:10.1039/C3SC52041B
Five [FeIIImYbIIIn] Cyclic Coordination Clusters (CCCs) which show completely different arrangements of their cyclic cores have been synthesised and characterised. These represent five out of seven compounds which were obtained by fine-tuning the reaction conditions (FeIII-source, LnIII-salt, chiral/nonchiral aminoalcohol ligands) used previously to synthesise the non-cyclic [Fe2Yb2(OH)2(teaH)2(O2CPh)6] compound 1. Thus the five new CCCs [Fe5Yb3(μ3-OH)(teaH)7(O2CPh)8](CF3SO3)·10MeCN (m = 5; n = 2, 2), [Fe4Yb2(μ-OH)(μ-OMe)2(Me-teaH)4(O2CPh)7]·3CH3CN (m = 4; n = 2, 3), [Fe3Yb2(μ-OH)(Me-teaH)4(O2CPh)6]·MeCN (m = 3; n = 2, 4), [Fe4Yb2(Me-tea)4(Me-teaH)2(OTs)2]·MeCN·3MeOH (m = 4; n = 2, 5) and [Fe10Yb10(Me-tea)10(Me-teaH)10(NO3)10]·21MeCN (m = 10; n = 10, 6) as well as the binuclear complex [Yb2(tipH2)2(O2CPh)4] (7) are reported. The formation of compounds 2, 3 and 4, which were obtained using [Fe3O(O2CCPh)6(H2O)3]+ as the source of FeIII, can be rationalised in terms of cleaving the triangular {FeIII3O} starting material into mononuclear and dinuclear FeIII/benzoate species. Furthermore, it was found that for compounds 3–6, the interplay of ligand chirality, hydrogen-bonding interactions and the nature of anionic species present are decisive directional influences on the resulting nature of the cyclic compounds.
Co-reporter:Nicolas Leblanc, Stephen Sproules, Karin Fink, Lionel Sanguinet, Olivier Alévêque, Eric Levillain, Patrick Rosa and Annie K. Powell
Chemical Science (2010-Present) 2016 - vol. 7(Issue 6) pp:NaN3828-3828
Publication Date(Web):2016/02/24
DOI:10.1039/C5SC04904K
To intimately combine a chelating ligand function with the numerous properties of a viologen-like redox-active centre would offer a rare possibility to design controllable multi-redox states, whose properties arise from strongly correlated phenomena between the organic ligand as well as with any metalloid coordinated centres. Such a concept previously proved to be feasible, however is not widely applicable owing to challenges in terms of synthesis, isolation, and aerial sensitivity of both the ligand and its metal complexes. Here we report the first stable example of such a redox-active molecule, N,N′-dimethyl-3,3′-biquinoxalinium2+/˙+/0 “methylbiquinoxen, MBqn2+/˙+/0”, which shows a rich redox chemistry and chelates a metal ion in the case of the metal complex [CdCl2(MBqn0)]. This goes beyond what is possible to achieve using viologens, which are limited by not providing chelation as well as having no accessible biradicaloid state, corresponding to the neutral direduced MBqn0 open-shell behaviour we observe here.
Co-reporter:Sebastian Schmidt, Denis Prodius, Ghenadie Novitchi, Valeriu Mereacre, George E. Kostakis and Annie K. Powell
Chemical Communications 2012 - vol. 48(Issue 79) pp:NaN9827-9827
Publication Date(Web):2012/08/02
DOI:10.1039/C2CC34361D
A new family of hexanuclear ferric-lanthanide [FeIII4LnIII2(Htea)4(Piv)6(N3)4] clusters, where LnIII = Er(1) and Lu(2) is reported. Variable temperature solid-state magnetic susceptibility studies of 1 and 2 reveal the presence of ferromagnetic (1) or competing anti- and ferromagnetic exchange interactions (2) between the constituent FeIII ions.
Co-reporter:Hua Xiang, Valeriu Mereacre, Yanhua Lan, Tong-Bu Lu, Christopher E. Anson and Annie K. Powell
Chemical Communications 2013 - vol. 49(Issue 67) pp:NaN7387-7387
Publication Date(Web):2013/05/09
DOI:10.1039/C3CC42416B
[FeIII2LnIII2(OH)2(L1)2(HL2)2(NO3)4(H2O)1½(MeOH)½]·6MeCN (Ln = Y (1), Dy (2); H2L1 = 2,3-dihydroxybenzaldehyde and H2L2 is the Schiff base of this aldehyde with furfurylamine) have unusually weak antiferromagnetic interactions between the FeIII centres in comparison with other (μ-dihydroxo)diiron(III) complexes. For 1, it was established that modulation of the hydroxo bridges by coordination to the YIII ions results in long Fe–O bonds and small Fe–O–Fe angles, leading to J = −0.4 cm−1. Analysis of the Mössbauer spectra reveals that the intramolecular magnetic field generated by the anisotropic DyIII ions in 2 is sufficient to overcome the Fe–Fe antiferromagnetic coupling and reorientate the FeIII moments into a ferromagnetic spin orientation.
Co-reporter:Ayuk M. Ako, Yanhua Lan, Oliver Hampe, Eduard Cremades, Eliseo Ruiz, Christopher E. Anson and Annie K. Powell
Chemical Communications 2014 - vol. 50(Issue 44) pp:NaN5850-5850
Publication Date(Web):2014/04/11
DOI:10.1039/C4CC01264J
Experimental and theoretical studies indicate that achieving the maximum possible ground spin state of ST = 83/2 for the mixed-valent Mn19 coordination cluster is insensitive to replacement of its eight μ3-N3 ligands by μ3-Cl, μ3-Br, μ3-OH or μ3-OMe, substantiating that the ferromagnetic interactions are indeed mediated mainly by the internal (μ4-O) ligands. The robustness of the inorganic {MnIII12MnII7(μ4-O)8} core is clear from the molecular structure and ESI-MS studies have shown that the structure of the Mn19 aggregate, and also of its Mn18Y analogue, are stable beyond the solid state.
Co-reporter:Denis Prodius, Hamid Saeed Shah, Jamshed Iqbal, Anastasia Macaeva, Anatoli Dimoglo, George E. Kostakis, Nicolas Zill, Fliur Macaev and Annie K. Powell
Chemical Communications 2014 - vol. 50(Issue 38) pp:NaN4890-4890
Publication Date(Web):2014/01/29
DOI:10.1039/C3CC49759C
Conversion of nitriles under mild conditions leads to a new class of primary amines, including room temperature ionic liquids, acting as efficient anticancer agents.
Co-reporter:Amer Baniodeh, Valeriu Mereacre, Nicola Magnani, Yanhua Lan, Juliusz A. Wolny, Volker Schünemann, Christopher E. Anson and Annie K. Powell
Chemical Communications 2013 - vol. 49(Issue 83) pp:NaN9668-9668
Publication Date(Web):2013/08/21
DOI:10.1039/C3CC45695A
The modulation of the magnetic anisotropy using the electronic features of the ligands was monitored by performing magnetic, spectroscopic and theoretical studies on a series of {Fe2Dy2} coordination clusters.
Co-reporter:Irina A. Kühne, Valeriu Mereacre, Christopher E. Anson and Annie K. Powell
Chemical Communications 2016 - vol. 52(Issue 5) pp:NaN1024-1024
Publication Date(Web):2015/11/13
DOI:10.1039/C5CC08887A
We report a family of isostructural nonanuclear FeIII–LnIII cyclic coordination clusters [FeIII6LnIII3(μ-OMe)9(vanox)6(benz)6]. (Ln = Tb (1), Dy (2), Ho (3), Er (4), Tm (5), Yb (6), Lu (7), Y (8) and Gd (9)), containing an odd number of metal ions. The planar cyclic coordination cluster cores are built up from three [Fe2Ln] subunits.
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![PHENOL, 2-[(E)-[(2-HYDROXYPHENYL)IMINO]METHYL]-6-METHOXY-](/data/chemimg/2648300/876062-80-5.png)
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o)-1,4-phenylene]](http://img.cochemist.com/ccimg/201100/201026-18-8.png)
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o)-1,4-phenylene]](http://img.cochemist.com/ccimg/201100/201026-18-8_b.png)
![Ethanol, 2,2'-[(2-pyridinylmethyl)imino]bis-](http://img.cochemist.com/ccimg/10200/10135-47-4.png)
![Ethanol, 2,2'-[(2-pyridinylmethyl)imino]bis-](http://img.cochemist.com/ccimg/10200/10135-47-4_b.png)
