Co-reporter:Lei Qin, Guo-Jun Zhou, You-Zhu Yu, Hiroyuki Nojiri, Christian Schröder, Richard E. P. Winpenny, and Yan-Zhen Zheng
Journal of the American Chemical Society November 15, 2017 Volume 139(Issue 45) pp:16405-16405
Publication Date(Web):October 16, 2017
DOI:10.1021/jacs.7b09996
The creation of a perfect hollow nanoscopic sphere of metal centers is clearly an unrealizable synthetic challenge. It is, however, an inspirational challenge from the viewpoint of chemical architecture and also as finite molecular species may provide unique microscopic insight into the origin and onset of phenomena such as topological spin-frustration effects found in infinite 2D and 3D systems. Herein, we report a series of high-symmetry gadolinium(III) (S = 7/2) polyhedra, Gd20, Gd32, Gd50, and Gd60, to test an approach based on assembling polymetallic fragments that contain different polygons. Structural analysis reveals that the Gd20 cage resembles a dodecahedron; the vertices of the Gd32 polyhedron exactly reveal symmetry Oh; Gd50 displays an unprecedented polyhedron in which an icosidodecahedron Gd30 core is encapsulated by an outer Gd20 dodecahedral shell with approximate Ih symmetry; and the Gd60 shows a truncated octahedron geometry. Experimental and theoretical magnetic studies show that this series produces the expected antiferromagnetic interaction that can be modeled based on classical spins at the Gd sites. From the magnetization analyses, we can roughly correlate the derivative bands to the Gd–O–Gd angles. Such a magneto-structural correlation may be used as “fingerprints” to identify these cages.
Co-reporter:Dr. Grigore A. Timco;Dr. Antonio Fernez;Andreas K. Kostopoulos;Dr. Christopher A. Muryn;Dr. Robin G. Pritchard;Dr. Ilya Strashnov;Dr. Inigo J. Vitorica-Yrezebal;Dr. George F. S. Whitehead; Dr. Richard E. P. Winpenny
Angewandte Chemie 2017 Volume 129(Issue 44) pp:13817-13820
Publication Date(Web):2017/10/23
DOI:10.1002/ange.201706679
AbstractA family of heterometallic [Cat][TixMO(x+1)(O2CtBu)2x+2] rings is reported where Cat=a secondary or tertiary alkyl ammonium ion, x=7, 8 or 9, and M=FeIII, GaIII, CrIII, InIII and AlIII. The structures are regular polygons with eight, nine or ten vertices with each edge bridged by an oxide and two pivalates. The size of the ring formed is controlled by the alkylammonium cation present. In each case a homometallic by-product is found [Cat][TixO(x+1)(O2CtBu)2x−1].
Co-reporter:Dr. Scott M. Lewis;Dr. Antonio Fernez;Dr. Guy A. DeRose;Dr. Matthew S. Hunt;Dr. George F. S. Whitehead;Agnese Lagzda;Hayden R. Alty;Dr. Jesus Ferro-Soria;Dr. Sarah Varey;Andreas K. Kostopoulos;Dr. Fredrik Schedin;Dr. Christopher A. Muryn;Dr. Grigore A. Timco; Axel Scherer; Stephen G. Yeates; Richard E. P. Winpenny
Angewandte Chemie International Edition 2017 Volume 56(Issue 24) pp:6749-6752
Publication Date(Web):2017/06/06
DOI:10.1002/anie.201700224
AbstractA new resist material for electron beam lithography has been created that is based on a supramolecular assembly. Initial studies revealed that with this supramolecular approach, high-resolution structures can be written that show unprecedented selectivity when exposed to etching conditions involving plasmas.
Co-reporter:Dr. Lei Qin;Jared Singleton;Wei-Peng Chen; Dr. Hiroyuki Nojiri; Dr. Larry Engelhardt; Dr. Richard E. P. Winpenny; Dr. Yan-Zhen Zheng
Angewandte Chemie 2017 Volume 129(Issue 52) pp:16798-16801
Publication Date(Web):2017/12/22
DOI:10.1002/ange.201709650
AbstractChromium lanthanide heterometallic wheel complexes {Cr8Ln8} (Ln=Gd, Dy and Y) with alternating metal centres are presented. Quantum Monte Carlo simulations reveal antiferromagnetic exchange-coupling constants with an average of 2.1 K within the {Cr8Gd8} wheel, which leads to a large ground spin state (ST=16) that is confirmed by magnetization studies up to 20 Tesla. The {Cr8Dy8} wheel is a single-molecule magnet.
Co-reporter:Dr. Scott M. Lewis;Dr. Antonio Fernez;Dr. Guy A. DeRose;Dr. Matthew S. Hunt;Dr. George F. S. Whitehead;Agnese Lagzda;Hayden R. Alty;Dr. Jesus Ferro-Soria;Dr. Sarah Varey;Andreas K. Kostopoulos;Dr. Fredrik Schedin;Dr. Christopher A. Muryn;Dr. Grigore A. Timco; Axel Scherer; Stephen G. Yeates; Richard E. P. Winpenny
Angewandte Chemie 2017 Volume 129(Issue 24) pp:6853-6856
Publication Date(Web):2017/06/06
DOI:10.1002/ange.201700224
AbstractA new resist material for electron beam lithography has been created that is based on a supramolecular assembly. Initial studies revealed that with this supramolecular approach, high-resolution structures can be written that show unprecedented selectivity when exposed to etching conditions involving plasmas.
Co-reporter:Dr. Lei Qin;Jared Singleton;Wei-Peng Chen; Dr. Hiroyuki Nojiri; Dr. Larry Engelhardt; Dr. Richard E. P. Winpenny; Dr. Yan-Zhen Zheng
Angewandte Chemie International Edition 2017 Volume 56(Issue 52) pp:16571-16574
Publication Date(Web):2017/12/22
DOI:10.1002/anie.201709650
AbstractChromium lanthanide heterometallic wheel complexes {Cr8Ln8} (Ln=Gd, Dy and Y) with alternating metal centres are presented. Quantum Monte Carlo simulations reveal antiferromagnetic exchange-coupling constants with an average of 2.1 K within the {Cr8Gd8} wheel, which leads to a large ground spin state (ST=16) that is confirmed by magnetization studies up to 20 Tesla. The {Cr8Dy8} wheel is a single-molecule magnet.
Co-reporter:Dr. Iñigo J. Vitórica-Yrezábal;Daniel Florin Sava;Dr. Grigore A. Timco;Dr. Martyn S. Brown;Mathew Savage;Harry G. W. Godfrey;Dr. Florian Moreau; Martin Schröder;Dr. Flor Siperstein; Lee Brammer;Dr. Sihai Yang;Dr. Martin P. Attfield;Dr. Joseph J. W. McDouall; Richard E. P. Winpenny
Angewandte Chemie International Edition 2017 Volume 56(Issue 20) pp:5527-5530
Publication Date(Web):2017/05/08
DOI:10.1002/anie.201701726
AbstractThe {Cr8} metallacrown [CrF(O2CtBu)2]8, containing a F-lined internal cavity, shows high selectivity for CO2 over N2. DFT calculations and absorption studies support the multiple binding of F-groups to the C-center of CO2 (C⋅⋅⋅F 3.190(9)–3.389(9) Å), as confirmed by single-crystal X-ray diffraction.
Co-reporter:Dr. Iñigo J. Vitórica-Yrezábal;Daniel Florin Sava;Dr. Grigore A. Timco;Dr. Martyn S. Brown;Mathew Savage;Harry G. W. Godfrey;Dr. Florian Moreau; Martin Schröder;Dr. Flor Siperstein; Lee Brammer;Dr. Sihai Yang;Dr. Martin P. Attfield;Dr. Joseph J. W. McDouall; Richard E. P. Winpenny
Angewandte Chemie 2017 Volume 129(Issue 20) pp:5619-5622
Publication Date(Web):2017/05/08
DOI:10.1002/ange.201701726
AbstractThe {Cr8} metallacrown [CrF(O2CtBu)2]8, containing a F-lined internal cavity, shows high selectivity for CO2 over N2. DFT calculations and absorption studies support the multiple binding of F-groups to the C-center of CO2 (C⋅⋅⋅F 3.190(9)–3.389(9) Å), as confirmed by single-crystal X-ray diffraction.
Co-reporter:Matthew Gregson, Nicholas F. Chilton, Ana-Maria Ariciu, Floriana Tuna, Iain F. Crowe, William Lewis, Alexander J. Blake, David Collison, Eric J. L. McInnes, Richard E. P. Winpenny and Stephen T. Liddle
Chemical Science 2016 vol. 7(Issue 1) pp:155-165
Publication Date(Web):23 Nov 2015
DOI:10.1039/C5SC03111G
We report a dysprosium(III) bis(methanediide) single molecule magnet (SMM) where stabilisation of the highly magnetic states and suppression of mixing of opposite magnetic projections is imposed by a linear arrangement of negatively-charged donor atoms supported by weak neutral donors. Treatment of [Ln(BIPMTMS)(BIPMTMSH)] [Ln = Dy, 1Dy; Y, 1Y; BIPMTMS = {C(PPh2NSiMe3)2}2−; BIPMTMSH = {HC(PPh2NSiMe3)2}−] with benzyl potassium/18-crown-6 ether (18C6) in THF afforded [Ln(BIPMTMS)2][K(18C6)(THF)2] [Ln = Dy, 2Dy; Y, 2Y]. AC magnetic measurements of 2Dy in zero DC field show temperature- and frequency-dependent SMM behaviour. Orbach relaxation dominates at high temperature, but at lower temperatures a second-order Raman process dominates. Complex 2Dy exhibits two thermally activated energy barriers (Ueff) of 721 and 813 K, the largest Ueff values for any monometallic dysprosium(III) complex. Dilution experiments confirm the molecular origin of this phenomenon. Complex 2Dy has rich magnetic dynamics; field-cooled (FC)/zero-field cooled (ZFC) susceptibility measurements show a clear divergence at 16 K, meaning the magnetic observables are out-of-equilibrium below this temperature, however the maximum in ZFC, which conventionally defines the blocking temperature, TB, is found at 10 K. Magnetic hysteresis is also observed in 10% 2Dy@2Y at these temperatures. Ab initio calculations suggest the lowest three Kramers doublets of the ground 6H15/2 multiplet of 2Dy are essentially pure, well-isolated |±15/2〉, |±13/2〉 and |±11/2〉 states quantised along the CDyC axis. Thermal relaxation occurs via the 4th and 5th doublets, verified experimentally for the first time, and calculated Ueff values of 742 and 810 K compare very well to experimental magnetism and luminescence data. This work validates a design strategy towards realising high-temperature SMMs and produces unusual spin relaxation behaviour where the magnetic observables are out-of-equilibrium some 6 K above the formal blocking temperature.
Co-reporter:Eufemio Moreno Pineda, Giulia Lorusso, Karzan H. Zangana, Elias Palacios, Jürgen Schnack, Marco Evangelisti, Richard E. P. Winpenny and Eric J. L. McInnes
Chemical Science 2016 vol. 7(Issue 8) pp:4891-4895
Publication Date(Web):25 Apr 2016
DOI:10.1039/C6SC01415A
We report the synthesis and structure of a molecular {Gd7} cage of the formula (iPr2NH2)6[Gd7(μ3-OH)3(CO3)6(O2CtBu)12] which has crystallographic C3h symmetry. Low temperature specific heat and adiabatic demagnetization experiments (the latter achieving temperatures below 100 mK), lead to the observation of the effects of both intramolecular dipolar interactions and geometric spin frustration. The dipolar interaction leads to a massive rearrangement of energy levels such that specific heat and entropy below 2 K are strongly modified while magnetic susceptibility and magnetization above 2 K are not affected. The consequences of these phenomena for low temperature magnetocaloric applications are discussed.
Co-reporter:Ze-Min Zhang, Karzan H. Zangana, Andreas K. Kostopoulos, Ming-Liang Tong and Richard E. P. Winpenny
Dalton Transactions 2016 vol. 45(Issue 22) pp:9041-9044
Publication Date(Web):10 May 2016
DOI:10.1039/C6DT00876C
Reaction of (aminomethyl)phosphonic acid (ampH2) with a mixture of gadolinium and cobalt pivalates under solvothermal conditions, led to a pseudo-icosahedral cage {Gd12}, which shows a large magnetocaloric effect (MCE).
Co-reporter:George F. S. Whitehead, Jesús Ferrando-Soria, Laura Carthy, Robin G. Pritchard, Simon J. Teat, Grigore A. Timco and Richard E. P. Winpenny
Dalton Transactions 2016 vol. 45(Issue 4) pp:1638-1647
Publication Date(Web):22 Dec 2015
DOI:10.1039/C5DT04062K
Here we present a series of linked cage complexes of functionalised variants of the octametallic ring {Cr7Ni} with the general formula [nPr2NH2][Cr7NiF8(O2CtBu)15(O2CR)], where HO2CR is a N-heterocycle containing carboxylic acid. These compounds are made by reacting [nPr2NH2][Cr7NiF8(O2CtBu)15(O2CR)] with a variety of simple metal salts and metal dimers. The carboxylic acids studied include iso-nicotinic acid, 3-(4-pyridyl)acrylic acid and 4-pyridazine carboxylic acid. These new linked cage complexes have been studied structurally and the study highlights the versatility of functionalised {Cr7Ni} as a Lewis base ligand. As {Cr7Ni} is a putative molecular electron spin qubit this work contributes to our understanding of the chemistry that might be required to assemble molecular spin qubits.
Co-reporter:Robert J. Woolfson;Dr. Grigore A. Timco;Dr. Alessro Chiesa;Dr. Inigo J. Vitorica-Yrezabal;Dr. Floriana Tuna;Dr. Tatiana Guidi; Eva Pavarini; Paolo Santini; Stefano Carretta; Richard E. P. Winpenny
Angewandte Chemie 2016 Volume 128( Issue 31) pp:9002-9005
Publication Date(Web):
DOI:10.1002/ange.201601734
Abstract
The first regular homometallic ring containing an odd number of metal centers is reported. The ring was synthesized by means of amine-templated self-assembly. Extensive physical characterization studies, including magnetic measurements, powder inelastic neutron scattering (INS), and DFT calculations, show that the molecule has a near perfect match to the expected behavior for a frustrated system with the lowest energy pair of S=1/2 spin states separated by only 0.1 meV (0.8 cm−1).
Co-reporter:Robert J. Woolfson;Dr. Grigore A. Timco;Dr. Alessro Chiesa;Dr. Inigo J. Vitorica-Yrezabal;Dr. Floriana Tuna;Dr. Tatiana Guidi; Eva Pavarini; Paolo Santini; Stefano Carretta; Richard E. P. Winpenny
Angewandte Chemie International Edition 2016 Volume 55( Issue 31) pp:8856-8859
Publication Date(Web):
DOI:10.1002/anie.201601734
Abstract
The first regular homometallic ring containing an odd number of metal centers is reported. The ring was synthesized by means of amine-templated self-assembly. Extensive physical characterization studies, including magnetic measurements, powder inelastic neutron scattering (INS), and DFT calculations, show that the molecule has a near perfect match to the expected behavior for a frustrated system with the lowest energy pair of S=1/2 spin states separated by only 0.1 meV (0.8 cm−1).
Co-reporter:Jesùs Ferrando-Soria; Antonio Fernandez; Eufemio Moreno Pineda; Sarah A. Varey; Ralph W. Adams; Iñigo J. Vitorica-Yrezabal; Floriana Tuna; Grigore A. Timco; Christopher A. Muryn
Journal of the American Chemical Society 2015 Volume 137(Issue 24) pp:7644-7647
Publication Date(Web):June 5, 2015
DOI:10.1021/jacs.5b04664
Here we show an elegant and general route to the assembly of a giant {M12C24} cage from 12 palladium ions (M) and 24 heterometallic octanuclear coordination cages (C = {Cr7Ni-Py2}). The molecule is 8 nm in size, and the methods for its synthesis and characterization provide a basis for future developments at this scale.
Co-reporter:Nicholas F. Chilton, Conrad A. P. Goodwin, David P. Mills and Richard E. P. Winpenny
Chemical Communications 2015 vol. 51(Issue 1) pp:101-103
Publication Date(Web):05 Nov 2014
DOI:10.1039/C4CC08312A
We report the first near-linear bis(amide) 4f-block compound and show that this novel structure, if implemented with dysprosium(III), would have unprecedented single molecule magnet (SMM) properties with an energy barrier, Ueff, for reorientation of magnetization of 1800 cm−1.
Co-reporter:Antonio Fernandez, Eufemio Moreno Pineda, Jesùs Ferrando-Soria, Eric J. L. McInnes, Grigore A. Timco and Richard E. P. Winpenny
Chemical Communications 2015 vol. 51(Issue 55) pp:11126-11129
Publication Date(Web):15 Jun 2015
DOI:10.1039/C5CC02216A
A hybrid organic–inorganic molecular daisy chain has been synthesised in one pot reaction. The molecule contains two {Cr6Zn2} rings linked through an organic molecule that acts as both template and ligand. Magnetic and spectroscopic data reveal the magnetic complexity of the daisy chain, which can be casted to two magnetic isomers through comparison of experimental and simulated data for Cr(III) chains.
Co-reporter:George F. S. Whitehead, Simon J. Teat, Kevin J. Gagnon, Grigore A. Timco and Richard E. P. Winpenny
Chemical Communications 2015 vol. 51(Issue 17) pp:3533-3536
Publication Date(Web):03 Feb 2015
DOI:10.1039/C4CC10035B
We present the first example of an extended 3D framework synthesised without the use of an isolable organic component. This is achieved by the combination of two cage complexes isolated and functionalised prior to synthesis; [nPr2NH2][Cr7NiF8(O2CtBu)14(O2CC5H4N)2] and [Fe2CoO(O2CtBu)6(HO2CtBu)3], where the former is as a bidentate linker, bridging between three nodes of the latter.
Co-reporter:Eufemio Moreno Pineda, Christian Heesing, Floriana Tuna, Yan-Zhen Zheng, Eric J. L. McInnes, Jürgen Schnack, and Richard E. P. Winpenny
Inorganic Chemistry 2015 Volume 54(Issue 13) pp:6331-6337
Publication Date(Web):June 10, 2015
DOI:10.1021/acs.inorgchem.5b00649
Two families of copper lanthanide phosphonate clusters have been obtained through reaction of [Cu2(O2CtBu)4(HO2CtBu)2] and either Ln(NO3)3·nH2O or [Ln2(O2CtBu)6(HO2CtBu)6] and tert-butylphosphonic acid or an amino-functionalized phosphonic acid. The clusters, with general formula [Cu(MeCN)4][Cu3Ln9(μ3-OH)7(O3PtBu)6(O2CtBu)15] and [Cu6Ln6(μ3-OH)6(O3PC(NH2)Me2)6(O2CtBu)12], were structurally characterized through single crystal X-ray diffraction and possess highly symmetric metal cores with approximately C3v and D3h point symmetry, respectively. We have investigated the possible application of the isotropic analogues in magnetic cooling, where we were able to observe that up to around 70% of the theoretical magnetic entropy change is obtained. Simulation of the magnetic data shows antiferromagnetic coupling between the spin centers, which explains the magnetic entropy value observed.
Co-reporter:Eufemio Moreno Pineda, Nicholas F. Chilton, Floriana Tuna, Richard E. P. Winpenny, and Eric J. L. McInnes
Inorganic Chemistry 2015 Volume 54(Issue 12) pp:5930-5941
Publication Date(Web):May 27, 2015
DOI:10.1021/acs.inorgchem.5b00746
A family of 3d–4f [MII2LnIII2(μ3-OH)2(O2CtBu)10]2– “butterflies” (where MII = Mg, Co, Ni, and Cu; LnIII = Y, Gd, Tb, Dy, Ho, and Er) and [MnIII2LnIII2(μ3-O)2(O2CtBu)10]2– molecules (where LnIII = Y, Gd, Tb, Dy, Ho, and Er) has been synthesized and characterized through single-crystal X-ray diffraction, SQUID magnetometry, and ab initio calculations. All dysprosium- and some erbium-containing tetramers showed frequency-dependent maxima in the out-of-phase component of the susceptibility associated with slow relaxation of magnetization, and hence, they are single-molecule magnets (SMMs). AC susceptibility measurements have shown that the SMM behavior is entirely intrinsic to the Dy and Er sites and the magnitude of the energy barrier is influenced by the interactions between the 4f and the 3d metal. A trend is observed between the strength of the 3d-4f exchange interaction between and the maximum observed in the χ″M(T).
Co-reporter:Karzan H. Zangana, Eufemio Moreno Pineda and Richard E. P. Winpenny
Dalton Transactions 2015 vol. 44(Issue 28) pp:12522-12525
Publication Date(Web):10 Jun 2015
DOI:10.1039/C5DT01786F
Two new tetrametallic lanthanide-phosphonate complexes have been structurally and magnetically characterised. The {Dy4} complex is a single molecule magnet.
Co-reporter:Dr. Antonio Fernez;Dr. Eufemio MorenoPineda;Dr. Christopher A. Muryn;Dr. Stephen Sproules;Dr. Fabrizio Moro;Dr. Grigore A. Timco; Eric J. L. McInnes; Richard E. P. Winpenny
Angewandte Chemie International Edition 2015 Volume 54( Issue 37) pp:10858-10861
Publication Date(Web):
DOI:10.1002/anie.201504487
Abstract
Hybrid [2]rotaxanes and pseudorotaxanes are reported where the magnetic interaction between dissimilar spins is controlled to create AB and AB2 electron spin systems, allowing independent control of weakly interacting S= centers.
Co-reporter:Dr. Antonio Fernez;Dr. Eufemio MorenoPineda;Dr. Christopher A. Muryn;Dr. Stephen Sproules;Dr. Fabrizio Moro;Dr. Grigore A. Timco; Eric J. L. McInnes; Richard E. P. Winpenny
Angewandte Chemie 2015 Volume 127( Issue 37) pp:11008-11011
Publication Date(Web):
DOI:10.1002/ange.201504487
Abstract
Hybrid [2]rotaxanes and pseudorotaxanes are reported where the magnetic interaction between dissimilar spins is controlled to create AB and AB2 electron spin systems, allowing independent control of weakly interacting S= centers.
Co-reporter: Eric J. L. McInnes;Dr. Grigore A. Timco;Dr. George F. S. Whitehead ; Richard E. P. Winpenny
Angewandte Chemie International Edition 2015 Volume 54( Issue 48) pp:14244-14269
Publication Date(Web):
DOI:10.1002/anie.201502730
Abstract
An enormous family of heterometallic rings has been made. The first were Cr7M rings where M=NiII, ZnII, MnII, and rings have been made with as many as fourteen metal centers in the cyclic structure. They are bridged externally by carboxylates, and internally by fluorides or a penta-deprotonated polyol. The size of the rings is controlled through templates which have included a range of ammonium or imidazolium ions, alkali metals and coordination compounds. The rings can be functionalized to act as ligands, and incorporated into hybrid organic–inorganic rotaxanes and into molecules containing up to 200 metal centers. Physical studies reported include: magnetic measurements, inelastic neutron scattering (including single crystal measurements), electron paramagnetic resonance spectroscopy (including measurements of phase memory times), NMR spectroscopy (both solution and solid state), and polarized neutron diffraction. The rings are hence ideal for understanding magnetism in elegant exchange-coupled systems.
Co-reporter: Eric J. L. McInnes;Dr. Grigore A. Timco;Dr. George F. S. Whitehead ; Richard E. P. Winpenny
Angewandte Chemie 2015 Volume 127( Issue 48) pp:14450-14477
Publication Date(Web):
DOI:10.1002/ange.201502730
Abstract
Heterometallische Ringe wurden in großer Zahl hergestellt, angefangen von den ersten Cr7M-Ringen mit M=NiII, ZnII und MnII bis hin zu Ringen mit vierzehn Metallen in der cyclischen Struktur. Bekannte Beispiele entweder außen durch Carboxylate oder innen durch Fluoride oder ein fünffach deprotoniertes Polyol verbrückt. Die Ringgröße wird durch Template gesteuert, z. B. durch Ammonium- oder Imidazoliumionen, Alkalimetalle oder Koordinationsverbindungen. Die Ringe können funktionalisiert werden und wirken dadurch als Liganden, sie lassen sich außerdem zum Aufbau von organisch-anorganischen Rotaxanen oder von Makromolekülen mit bis zu 200 Metallzentren verwenden. Eine Reihe von physikalischen Studien wurde an heterometallischen Ringen durchgeführt, darunter magnetische Messungen, inelastische Neutronenstreuung (einschließlich Einkristallmessungen), paramagnetische Elektronenresonanzspektroskopie (einschließlich Messungen der Phasengedächtniszeiten), NMR-Spektroskopie (Lösung und Festkörper) und polarisierte Neutronenstreuung. Die Ringe sind somit ideale Modellsystem, um Einblicke in den Magnetismus bei austauschgekoppelten Systemen zu gewinnen.
Co-reporter:Elena Garlatti ; Morten A. Albring ; Michael L. Baker ; Rebecca J. Docherty ; Hannu Mutka ; Tatiana Guidi ; Victoria Garcia Sakai ; George F. S. Whitehead ; Robin G. Pritchard ; Grigore A. Timco ; Floriana Tuna ; Giuseppe Amoretti ; Stefano Carretta ; Paolo Santini ; Giulia Lorusso ; Marco Affronte ; Eric J. L. McInnes ; David Collison
Journal of the American Chemical Society 2014 Volume 136(Issue 27) pp:9763-9772
Publication Date(Web):June 26, 2014
DOI:10.1021/ja5047445
Compounds of general formula [Cr7MF3(Etglu)(O2CtBu)15(Phpy)] [H5Etglu = N-ethyl-d-glucamine; Phpy = 4-phenylpyridine; M = Zn (1), Mn (2), Ni (3)] have been prepared. The structures contain an irregular octagon of metal sites formed around the penta-deprotonated Etglu5– ligand; the chirality of N-ethyl-d-glucamine is retained in the final product. The seven CrIII sites have a range of coordination environments, and the divalent metal site is crystallographically identified and has a Phpy ligand attached to it. By using complementary experimental techniques, including magnetization and specific heat measurements, inelastic neutron scattering, and electron paramagnetic resonance spectroscopy, we have investigated the magnetic features of this family of {Cr7M} rings. Microscopic parameters of the spin Hamiltonian have been determined as a result of best fits of the different experimental data, allowing a direct comparison with corresponding parameters found in the parent compounds. We examine whether these parameters can be transferred between compounds and compare them with those of an earlier family of heterometallic rings.
Co-reporter:George F. S. Whitehead, Jesùs Ferrando-Soria, Lorna G. Christie, Nicholas F. Chilton, Grigore A. Timco, Fabrizio Moro and Richard E. P. Winpenny
Chemical Science 2014 vol. 5(Issue 1) pp:235-239
Publication Date(Web):22 Oct 2013
DOI:10.1039/C3SC52095A
The synthesis, structures and magnetism of a new nano-scale constructs using carboxylic acid functionalised {Cr7Ni} rings are reported. Well-established carboxylate chemistry is used to synthesise of spectacular assemblies including a {Zn4O} tetrahedron surrounded by an octahedron of {Cr7Ni} rings.
Co-reporter:Karzan H. Zangana, Eufemio Moreno Pineda, Eric J. L. McInnes, Jürgen Schnack and Richard E. P. Winpenny
Chemical Communications 2014 vol. 50(Issue 12) pp:1438-1440
Publication Date(Web):20 Dec 2013
DOI:10.1039/C3CC48708C
Two {Ln10} cages are reported (Ln = Dy or Gd) which feature a nine-metal ring surrounding a central metal site. Magnetic studies show weak anti-ferromagnetic exchange around the nine-metal ring, which should create spin frustration.
Co-reporter:Eufemio Moreno Pineda, Floriana Tuna, Yan-Zhen Zheng, Simon J. Teat, Richard E. P. Winpenny, Jürgen Schnack, and Eric J. L. McInnes
Inorganic Chemistry 2014 Volume 53(Issue 6) pp:3032-3038
Publication Date(Web):March 6, 2014
DOI:10.1021/ic402839q
Reaction of [Fe3(μ3-O)(O2CtBu)6(HO2CtBu)3](O2CtBu) and [Ln2(O2CtBu)6(HO2CtBu)6] (Ln = lanthanide) with three different phosphonic acids produce a family of highly symmetrical {Fe6Ln6P6} clusters with general formula [Fe6Ln6(μ3-O)2(CO3)(O3PR)6(O2CtBu)18], where R = methyl 1, phenyl 2, or n-hexyl 3. All the clusters present an analogous metal frame to the previously reported {Ni6Ln6P6} both being related to the well-known Wells–Dawson ion from polyoxometallate chemistry. These highly symmetrical clusters have, or approximate very closely to, D3d point symmetry. Both FeIII and GdIII ions are magnetically isotropic and could thus exhibit promising magnetocaloric properties; hence we investigated the {Fe6Gd6P6} compounds accordingly. Modeling the magnetic data of [Fe6Gd6(μ3-O)2(CO3)(O3PPh)6(O2CtBu)18] by the finite-temperature Lanczos method gave a strong antiferromagnetic Fe···Fe interaction (JFe–Fe = −30 cm–1) and very weak Gd···Gd and Gd···Fe exchange interactions (|J| < 0.1 cm–1). The strong antiferromagnetic Fe···Fe interaction could account for the relatively smaller −ΔSm value observed, compared against the {Ni6Gd6P6} analogues.
Co-reporter:Karzan H. Zangana, Eufemio Moreno Pineda and Richard E. P. Winpenny
Dalton Transactions 2014 vol. 43(Issue 45) pp:17101-17107
Publication Date(Web):13 Oct 2014
DOI:10.1039/C4DT02630F
The synthesis, structures and magnetic properties of a family of lanthanide complexes containing phosphonate ligands are reported. Reaction of hydrated lanthanide nitrate and tbutylphosphonic acid under reflux conditions in iso-butanol, in the presence of pivalic acid as a co-ligand produced five new lanthanide complexes; pyridine (py) was present as a base. The compounds formed are tetrametallic, with the general formula [pyH]4[Ln4(μ3-OH)(O3PtBu)3(HO3PtBu)(O2CtBu)2(NO3)6] where Ln = GdIII, 1; TbIII, 2; DyIII, 3; HoIII, 4 and ErIII, 5. The metal sites within the complexes lie on the vertices of a triangle-based pyramid, with phosphonate ligands on the triangular faces linking the apical Ln site to the Ln sites in the base. Each lanthanide(III) site is eight-coordinate. Magnetic studies of the compounds show a decline in the product χMT with T; modelling the behaviour of 1 shows anti-ferromagnetic exchange between GdIII centres within the triangle with a negligible interaction to the fourth GdIII centre at the apex of the trigonal pyramid.
Co-reporter:Karzan H. Zangana, Eufemio Moreno Pineda, Iñigo J. Vitorica-Yrezabal, Eric J. L. McInnes and Richard E. P. Winpenny
Dalton Transactions 2014 vol. 43(Issue 35) pp:13242-13249
Publication Date(Web):29 Jul 2014
DOI:10.1039/C4DT01264J
The preparation and structural characterisation of five 3d–4f mixed metal phosphonate cages with general formula [CrIII6LnIII2(μ3-O)2(H2O)2(O3PtBu)4(O2CtBu)12(HOiBu)2(iPrNH2)2] where LnIII = La, 1; Tb, 3; Dy, 4; Ho, 5 and [CrIII6GdIII2(μ3-O)2(H2O)2(O3PtBu)4(O2CtBu)12(HOiBu)4] (2) are reported. The structure contains two oxo-centred {Cr3} triangles, bridged by phosphonates and lanthanides. The magnetic behaviour of 1 has been modelled as two non-interacting isosceles triangles, involving two antiferromagnetic interactions (J1 = −8.8 cm−1) with a smaller ferromagnetic interaction for the unique edge of the triangle (J2 = +1.3 cm−1) giving an isolated S = 3/2 ground state per triangle. The quartet ground state has been proven through simulation of electron paramagnetic resonance (EPR) spectra obtained at the X- and Q-band. EPR simulations have also resulted in the introduction of small single-ion Zero Field Splitting (ZFS) parameters D = ±0.19 cm−1 and rhombic term E = ±0.02 cm−1, which are consistent with strong exchange limit calculations for an isolated S = 3/2 (D = ±0.22 and E = ±0.018 cm−1).
Co-reporter:Grigore A. Timco, Eric J. L. McInnes and Richard E. P. Winpenny
Chemical Society Reviews 2013 vol. 42(Issue 4) pp:1796-1806
Publication Date(Web):18 Sep 2012
DOI:10.1039/C2CS35232J
Heterometallic rings of general formula [Cat][M7M′F8(O2CtBu)8] (M = a trivalent metal, M′ = a divalent metal, cat = a secondary ammonium cation, caesium or rubidium) contain an octagon of metal centres with each metal–metal edge bridged by a fluoride and two carboxylates. The rings when M = CrIII give remarkably beautiful EPR and INS spectra, and allow us to examine new techniques. Use of these techniques allows us to study the models used to describe magnetic behaviour in exchange coupled systems. In this tutorial review we discuss the two main approaches to modelling magnetic data – the strong exchange limit and the microscopic Hamiltonian approaches, aiming to explain the major differences between the two approaches. We also describe some more esoteric measurements and theories.
Co-reporter:Harapriya Rath, Grigore A. Timco, Valdis Corradini, Alberto Ghirri, Umberto del Pennino, Antonio Fernandez, Robin G. Pritchard, Christopher A. Muryn, Marco Affronte and Richard E. P. Winpenny
Chemical Communications 2013 vol. 49(Issue 33) pp:3404-3406
Publication Date(Web):19 Mar 2013
DOI:10.1039/C3CC38699F
Hybrid organic–inorganic [2]- and [3]rotaxanes have been synthesised, and their ability to bind to Au surfaces studied; the length of the tethering group is found to control how the supramolecular assembly binds to the surface and we find that [2]rotaxanes show improved stability over previous studies of simple inorganic rings.
Co-reporter:George F. S. Whitehead, Bryony Cross, Laura Carthy, Victoria A. Milway, Harapriya Rath, Antonio Fernandez, Sarah L. Heath, Christopher A. Muryn, Robin G. Pritchard, Simon J. Teat, Grigore A. Timco and Richard E. P. Winpenny
Chemical Communications 2013 vol. 49(Issue 65) pp:7195-7197
Publication Date(Web):20 Jun 2013
DOI:10.1039/C3CC42300J
Coordination polymers and metal–organic rotaxane frameworks are reported where the organic linker is replaced by functionalised inorganic clusters that act as bridging ligands.
Co-reporter:Eufemio Moreno Pineda ; Floriana Tuna ; Yan-Zhen Zheng ; Richard E. P. Winpenny ;Eric J. L. McInnes
Inorganic Chemistry 2013 Volume 52(Issue 23) pp:13702-13707
Publication Date(Web):November 12, 2013
DOI:10.1021/ic402296t
Five clusters with the general formula [Ni6Gd6(μ3-OH)2(μ2-OAc)2(O3PR)6(O2CtBu)16], where R = methyl (1), phenyl (2), n-hexyl (3), benzyl (4), n-octyl (5), have been prepared. All of the clusters have a {Ni6Gd6P6} core that can be related to the Wells–Dawson ion. We have also prepared analogues where the gadolinium is replaced with diamagnetic yttrium: [Ni6Y6(μ3-OH)2(μ2-OAc)2(O3PR)6(O2CtBu)16] (R = methyl (6), n-hexyl (7), benzyl (8), n-octyl (9)), allowing the magnetic exchange within the {Ni3} units to be analyzed by modeling as the sum of two noninteracting isosceles triangles. The variation in the magnetic entropy changes for magnetization (−ΔSM) among compounds 1–5 could be attributed not only to the molecular weight of the compounds but also to intramolecular magnetic interactions.
Co-reporter:Karzan H. Zangana, Eufemio Moreno Pineda, Jürgen Schnack and Richard E. P. Winpenny
Dalton Transactions 2013 vol. 42(Issue 39) pp:14045-14048
Publication Date(Web):22 Aug 2013
DOI:10.1039/C3DT52086B
Three octanuclear phosphonate clusters, formulated as [Ln8(O3PtBu)6(μ3-OH)2(H2O)2(HOiBu)(O2CtBu)12](NH3iPr)2 (Ln = Gd, Dy and Tb), were synthesised by refluxing a mixture of pivalic acid (HO2CtBu), Ln(NO3)3·6H2O, tert-Butyl phosphonic acid (H2O3PtBu) and isopropylamine (iPrNH2) in isobutyl alcoholiBuOH.
Co-reporter:George F. S. Whitehead;Dr. Fabrizio Moro;Dr. Grigore A. Timco;Dr. Wolfgang Wernsdorfer;Dr. Simon J. Teat;Dr. Richard E. P. Winpenny
Angewandte Chemie International Edition 2013 Volume 52( Issue 38) pp:9932-9935
Publication Date(Web):
DOI:10.1002/anie.201304817
Co-reporter:Ian Casson, Christopher A. Muryn, Floriana Tuna, Jürgen Schnack, Richard E.P. Winpenny
Polyhedron 2013 Volume 64() pp:59-62
Publication Date(Web):12 November 2013
DOI:10.1016/j.poly.2013.02.028
The synthesis, structure and magnetic properties of an octametallic iron(III) ring is reported. Alternate edges of the ring are bridged by a hydroxide and two pivalates, or by one pivalate and two phenoxides. By addition of biphenol to the reaction a hexadecametallic iron(III) cage can be made where the 16 metals are arranged in two linked {Fe8} rings. The rings are staggered with respect to one another, and lie on the vertices of an octagonal anti-prism. Magnetic studies on the octametallic ring allows exchange parameters to be obtained. Similar studies on the {Fe16} barrel shows the exchange interactions within the rings to be similar, with a significant paramagnetic impurity present.This paper reports a very unusual {Fe16} cage based on two linked octagonal rings. The resulting structure is a octagonal anti-prism. Magnetic measurements are reported on this compound and on a parent {Fe8} ring.
Co-reporter:George F. S. Whitehead;Dr. Fabrizio Moro;Dr. Grigore A. Timco;Dr. Wolfgang Wernsdorfer;Dr. Simon J. Teat;Dr. Richard E. P. Winpenny
Angewandte Chemie 2013 Volume 125( Issue 38) pp:10116-10119
Publication Date(Web):
DOI:10.1002/ange.201304817
Co-reporter:Scott A. Sulway, Richard A. Layfield, Floriana Tuna, Wolfgang Wernsdorfer and Richard E. P. Winpenny
Chemical Communications 2012 vol. 48(Issue 10) pp:1508-1510
Publication Date(Web):16 Sep 2011
DOI:10.1039/C1CC14643B
[Cp2Dy(thf)(μ-Cl)]2 (2) was synthesized from [Cp2Dy(μ-Cl)]n, which crystalizes as two polymorphs, with n = 2 (1a) or ∞ (1b). All three compounds show slow relaxation of magnetization, and in 2 the quantum tunnelling was found to be exchange-biased.
Co-reporter:Thomas B. Faust, Floriana Tuna, Grigore A. Timco, Marco Affronte, Valerio Bellini, Wolfgang Wernsdorfer and Richard E. P. Winpenny
Dalton Transactions 2012 vol. 41(Issue 44) pp:13626-13631
Publication Date(Web):21 Jun 2012
DOI:10.1039/C2DT31292A
A series of heteroaromatic bridging ligands are employed in the synthesis of a family of paramagnetic, heterometallic ring dimers. The extent of spin propagation between the rings via the organic conduit is investigated through micro-SQUID magnetometry and EPR spectroscopy from which conclusions over the mechanism of spin-communication are drawn.
Co-reporter:Dr. Yan-Zhen Zheng;Eufemio Moreno Pineda;Dr. Madeleine Helliwell;Dr. Richard E. P. Winpenny
Chemistry - A European Journal 2012 Volume 18( Issue 14) pp:4161-4165
Publication Date(Web):
DOI:10.1002/chem.201200152
Co-reporter:Michael L. Baker;Grigore A. Timco;Stergios Piligkos;Jennifer S. Mathieson;Hannu Mutka;Floriana Tuna;Piotr Kozłowski;Michał Antkowiak;Tatiana Guidi;Tulika Gupta;Harapriya Rath;Robert J. Woolfson;Grzegorz Kamieniarz;Robin G. Pritchard;Høgni Weihe;Leroy Cronin;Gopalan Rajaraman;David Collison;Eric J. L. McInnes
PNAS 2012 Volume 109 (Issue 47 ) pp:19113-19118
Publication Date(Web):2012-11-20
DOI:10.1073/pnas.1213127109
The term “frustration” in the context of magnetism was originally used by P. W. Anderson and quickly adopted for application
to the description of spin glasses and later to very special lattice types, such as the kagomé. The original use of the term
was to describe systems with competing antiferromagnetic interactions and is important in current condensed matter physics
in areas such as the description of emergent magnetic monopoles in spin ice. Within molecular magnetism, at least two very
different definitions of frustration are used. Here we report the synthesis and characterization of unusual nine-metal rings,
using magnetic measurements and inelastic neutron scattering, supported by density functional theory calculations. These compounds
show different electronic/magnetic structures caused by frustration, and the findings lead us to propose a classification
for frustration within molecular magnets that encompasses and clarifies all previous definitions.
Co-reporter:YanZhen Zheng
Science China Chemistry 2012 Volume 55( Issue 6) pp:910-913
Publication Date(Web):2012 June
DOI:10.1007/s11426-012-4571-4
Three new iron(III) phosphonate cage-like complexes with [Fe4], [Fe9] and [Fe14] cores have been synthesized by solvothermal reaction with various starting materials. Magnetic studies show overall antiferromagnetic interaction presented in these cages.
Co-reporter:Grigore A. Timco, Thomas B. Faust, Floriana Tuna and Richard E. P. Winpenny
Chemical Society Reviews 2011 vol. 40(Issue 6) pp:3067-3075
Publication Date(Web):17 Jan 2011
DOI:10.1039/C0CS00151A
Linking polymetallic cages can be a method for creating new structures and new properties. In this tutorial review we use heterometallic anti-ferromagnetically coupled rings (AF-rings) as exemplars for three approaches that can be used to link cage compounds. The first of three routes involves an ion-pair interaction supported by hydrogen-bonding interactions, which allows the synthesis of hybrid rotaxanes among other materials. The second route involves functionalising the exterior of the AF-ring so that it will act as a Lewis base; complexes involving coordination of pyridine to bridging monometallic and dimetallic fragments are discussed. The third route involves creating a vacancy on one site of the AF-ring, and then using the ring as a Lewis acid. Di-imine ligands can then be used to link the AF-rings into dimers. A brief discussion of the physical properties of these systems is also included.
Co-reporter:Yan-Zhen Zheng ; Marco Evangelisti ; Floriana Tuna
Journal of the American Chemical Society 2011 Volume 134(Issue 2) pp:1057-1065
Publication Date(Web):December 14, 2011
DOI:10.1021/ja208367k
The synthesis, structures, and magnetic properties of six families of cobalt–lanthanide mixed-metal phosphonate complexes are reported in this Article. These six families can be divided into two structural types: grids, where the metal centers lie in a single plane, and cages. The grids include [4 × 3] {Co8Ln4}, [3 × 3] {Co4Ln6}, and [2 × 2] {Co4Ln2} families and a [4 × 4] {Co8Ln8} family where the central 2 × 2 square is rotated with respect to the external square. The cages include {Co6Ln8} and {Co8Ln2} families. Magnetic studies have been performed for these compounds, and for each family, the maximum magnetocaloric effect (MCE) has been observed for the Ln = Gd derivative, with a smaller MCE for the compounds containing magnetically anisotropic 4f-ions. The resulting entropy changes of the gadolinium derivatives are (for 3 K and 7 T) 11.8 J kg–1 K–1 for {Co8Gd2}; 20.0 J kg–1 K–1 for {Co4Gd2}; 21.1 J kg–1 K–1 for {Co8Gd4}; 21.4 J kg–1 K–1 for {Co8Gd8}; 23.6 J kg–1 K–1 for {Co4Gd6}; and 28.6 J kg–1 K–1 for {Co6Gd8}, from which we can see these values are proportional to the percentage of the gadolinium in the core.
Co-reporter:Yan-Zhen Zheng, Marco Evangelisti and Richard E. P. Winpenny
Chemical Science 2011 vol. 2(Issue 1) pp:99-102
Publication Date(Web):24 Sep 2010
DOI:10.1039/C0SC00371A
Three 3d–4f phosphonate complexes, [CoII8GdIII8(μ3-OH)4(NO3)4(O3PtBu)8(O2CtBu)16], [CoII8GdIII4(O3PtBu)6(O2CtBu)16] and [CoII4GdIII6(O3PCH2Ph)6(O2CtBu)14(MeCN)2], have been synthesized and have structures that can be related to molecular grids. Magnetic studies show they have promise as low temperature magnetic refrigerants.
Co-reporter:Andrew McRobbie, Asad R. Sarwar, Steven Yeninas, Harriott Nowell, Michael L. Baker, David Allan, Marshall Luban, Christopher A. Muryn, Robin G. Pritchard, Ruslan Prozorov, Grigore A. Timco, Floriana Tuna, George F. S. Whitehead and Richard E. P. Winpenny
Chemical Communications 2011 vol. 47(Issue 22) pp:6251-6253
Publication Date(Web):06 May 2011
DOI:10.1039/C1CC11516B
Hexametallic chromium(III) chains can act as fluoride donor ligands to lanthanide ions giving {(Cr6)Lnx}n complexes; preliminary spectroscopic studies are reported.
Co-reporter:Robin J. Blagg, Floriana Tuna, Eric J. L. McInnes and Richard E. P. Winpenny
Chemical Communications 2011 vol. 47(Issue 38) pp:10587-10589
Publication Date(Web):01 Sep 2011
DOI:10.1039/C1CC14186D
Pentametallic Ln complexes of formula [Ln5O(OiPr)13] have been made, where LnIII = Sm, Gd, Tb, Ho and Er; slow magnetisation relaxation to 33 K is observed for the Ho complex with an energy barrier of ca. 400 K.
Co-reporter:Kandasamy Gopal, Floriana Tuna and Richard E. P. Winpenny
Dalton Transactions 2011 vol. 40(Issue 45) pp:12044-12047
Publication Date(Web):07 Sep 2011
DOI:10.1039/C1DT10855G
Two new iron(III)-potassium phosphonate cage complexes with {K2Fe6} and {K2Fe4} cores are reported. Magnetic studies reveal antiferromagnetic interactions between the Fe(III) centres occur in these cages.
Co-reporter:Michael L. Baker, Stergios Piligkos, Alberto Bianchi, Stefano Carretta, David Collison, Joseph J. W. McDouall, Eric J. L. McInnes, Hannu Mutka, Grigore A. Timco, Floriana Tuna, Prabha Vadivelu, Høgni Weihe, Hans U. Güdel and Richard E. P. Winpenny
Dalton Transactions 2011 vol. 40(Issue 34) pp:8533-8539
Publication Date(Web):05 Jul 2011
DOI:10.1039/C1DT10547G
An investigation into the physical consequences of including a Jahn–Teller distorted CuII ion within an antiferromagnetically coupled ring, [R2NH2][Cr7CuF8((O2CtBu)16)] is reported. Inelastic neutron scattering (INS) and electron paramagnetic resonance (EPR) spectroscopic data are simulated using a microscopic spin Hamiltonian, and show that the two Cr–Cu exchange interactions must be inequivalent. One Cr–Cu exchange is found to be antiferromagnetic and the other ferromagnetic. The geometry of the Jahn–Teller elongation is deduced from these results, and shows that a Jahn–Teller elongation axis must lie in the plane of the Cr7Cu wheel; the elongation is not observed by X-ray crystallography, due to positional disorder of the Cu site within the wheel. An electronic structure calculation confirms the structural distortion of the Cu site.
Co-reporter:Thomas B. Faust;Dr. Valerio Bellini;Dr. Andrea Cini;Dr. Stefano Carretta;Dr. Giulia Lorusso;Dr. David R. Allan;Dr. Laura Carthy; David Collison;Rebecca J. Docherty;Jasbinder Kenyon;John Machin; Eric J. L. McInnes;Dr. Christopher A. Muryn;Dr. Harriott Nowell;Dr. Robin G. Pritchard;Dr. Simon J. Teat;Dr. Grigore A. Timco;Dr. Floriana Tuna;George F. S. Whitehead;Dr. Wolfgang Wernsdorfer; Marco Affronte; Richard E. P. Winpenny
Chemistry - A European Journal 2011 Volume 17( Issue 50) pp:14020-14030
Publication Date(Web):
DOI:10.1002/chem.201101785
Abstract
We present a synthetic, structural, theoretical, and spectroscopic study of a family of heterometallic ring dimers which have the formula [{Cr7NiF3(Etglu)(O2CtBu)15}2(NLN)], in which Etglu is the pentadeprotonated form of the sugar N-ethyl-D-glucamine, and NLN is an aromatic bridging diimine ligand. By varying NLN we are able to adjust the strength of the interaction between rings with the aim of understanding how to tune our system to achieve weak magnetic communication between the spins, a prerequisite for quantum entanglement. Micro-SQUID and EPR data reveal that the magnetic coupling between rings is partly related to the through-bond distance between the spin centers, but also depends on spin-polarization mechanisms and torsion angles between aromatic rings. Density functional theory (DFT) calculations allow us to make predictions of how such chemically variable parameters could be used to tune very precisely the interaction in such systems. For possible applications in quantum information processing and molecular spintronics, such precise control is essential.
Co-reporter:Dr. Robin J. Blagg;Dr. Christopher A. Muryn; Eric J. L. McInnes;Dr. Floriana Tuna ; Richard E. P. Winpenny
Angewandte Chemie International Edition 2011 Volume 50( Issue 29) pp:6530-6533
Publication Date(Web):
DOI:10.1002/anie.201101932
Co-reporter:Dr. Yan-Zhen Zheng;Dr. Marco Evangelisti;Dr. Richard E. P. Winpenny
Angewandte Chemie International Edition 2011 Volume 50( Issue 16) pp:3692-3695
Publication Date(Web):
DOI:10.1002/anie.201008074
Co-reporter:Dr. Robin J. Blagg;Dr. Christopher A. Muryn; Eric J. L. McInnes;Dr. Floriana Tuna ; Richard E. P. Winpenny
Angewandte Chemie 2011 Volume 123( Issue 29) pp:6660-6663
Publication Date(Web):
DOI:10.1002/ange.201101932
Co-reporter:Dr. Yan-Zhen Zheng;Dr. Marco Evangelisti;Dr. Richard E. P. Winpenny
Angewandte Chemie 2011 Volume 123( Issue 16) pp:3776-3779
Publication Date(Web):
DOI:10.1002/ange.201008074
Co-reporter:Thomas B. Faust, Paul G. Heath, Christopher A. Muryn, Grigore A. Timco and Richard E. P. Winpenny
Chemical Communications 2010 vol. 46(Issue 34) pp:6258-6260
Publication Date(Web):09 Aug 2010
DOI:10.1039/C0CC01188F
A fluoro-metallocrown selectively binds caesium, extracting it from aqueous solutions into an organic layer; the binding of Cs is monitored by 1H-NMR of the paramagnetic complexes.
Co-reporter:Shoaib Ali, Christopher A. Muryn, Floriana Tuna and Richard E. P. Winpenny
Dalton Transactions 2010 vol. 39(Issue 1) pp:124-131
Publication Date(Web):20 Nov 2009
DOI:10.1039/B913467K
A polynucleating oxygen donor ligand based on condensation of p-chlorophenylstibonic acid (ArSbO3H2) and t-butylphosphonic acid is reported. [(SbAr)2O(HO3PtBu)6] contains two antimony centres, bridged by an oxide and two hydrogen phosphonates. Reaction with copper acetate under solvothermal conditions produces four new polymetallic copper complexes. With pyridine used as a base the major product is a tetracopper cage, [Cu4O2(SbAr)2(O3PtBu)2(O2CMe)2(OMe)6], with the four copper centres arranged in a rhombus; a minor product is a tricopper complex, [Cu3O4(SbAr)2(O3PtBu)4(py)3]. With LiOMe as base the major product is again the tetranuclear cage, but the minor product is a heterometallic cage, [Cu5Li4O6(SbAr)4(O3PtBu)6(O2CMe)2(OMe)4 (MeOH)4]. With 2,6-lutidine as base an octametallic complex is formed, [Cu8O4(SbAr)2(O3PtBu)6(O2CMe)4(lutidine)2]. Magnetic studies show both anti-ferromagnetic and weak ferromagnetic exchange between the copper centres in these new complexes.
Co-reporter:Shoaib Ali, Christopher A. Muryn, Floriana Tuna and Richard E. P. Winpenny
Dalton Transactions 2010 vol. 39(Issue 40) pp:9588-9597
Publication Date(Web):03 Sep 2010
DOI:10.1039/C0DT00482K
The polynucleating oxygen donor ligands, [(SbAr)4O2(PhPO3H)4(PhPO3)4] 1 and [(SbAr)2O(HO3PtBu)6] 2, based on condensation of p-chlorophenylstibonic acid (ArSbO3H2) and phosphonic acids, were used to prepare polymetallic cobalt(II) complexes. Reaction of 1 with cobalt acetate under solvothermal conditions produces three different types of polymetallic cobalt complexes. With LiOMe/pyridine as base in MeOH a dinuclear cobalt cage, [Co2(SbAr)4O4(O3PPh)4(OMe)4py2] 3, is formed, with four Sb(II) and two Co(II) centres bridged by μ3-oxides and phosphonates. The pyridine in the structure can be replaced by 3-picoline 4, 4-picoline 5, quinoline 6, 1,2-diazole 7, 4-phenylpyridine 8, 4-ethyl pyridine 9 and methanol 10. Using pyrazine (pyz) instead of pyridine under the same conditions a polymer, [Co2(SbAr)4O4(O3PPh)4(OMe)4(C4H4N2)]n11, is formed. A similar 1D-polymer forms with 4,4′-bipyridyl-ethylene 12 in place of pyrazine. With Et3N/pyridine as base in MeCN a tetranuclear cobalt cage, [Co4(SbAr)5O9(O3PPh)6(py)4] 13, with five Sb(II) centres forming a “bowtie” and bridging to four Co(II) centres by phosphonates and μ3-oxides, is formed. The reaction of 2 with cobalt acetate using LiOMe/pyridine as base in methanol, under solvothermal conditions, produces a dinuclear Co(II) complex, [Co2(SbAr)2(O3PtBu)3O2(OMe)2(py)2] 14, with two CoII and two Sb centres at the vertices of a distorted tetrahedron. Magnetic measurements on selected number of these cobalt cages are reported.
Co-reporter:Viswanathan Baskar, Kandasamy Gopal, Madeleine Helliwell, Floriana Tuna, Wolfgang Wernsdorfer and Richard E. P. Winpenny
Dalton Transactions 2010 vol. 39(Issue 20) pp:4747-4750
Publication Date(Web):12 Apr 2010
DOI:10.1039/B927114G
Three new Cu–Ln cage complexes bridged by phosphonates and acetates are reported; one—a Cu24Dy8 cage—is a new single molecule magnet (SMM).
Co-reporter:Yan-Zhen Zheng, Barbara A. Breeze, Grigore A. Timco, Floriana Tuna and Richard E. P. Winpenny
Dalton Transactions 2010 vol. 39(Issue 27) pp:6175-6177
Publication Date(Web):07 Jun 2010
DOI:10.1039/C0DT00017E
Two new Co(II)–Cr(III) phosphonate clusters with [CoII4CrIII4] and [CoII8CrIII4] cores have been synthesized by a displacement reaction from a pre-formed heterometallic carboxylate cage. Magnetic studies show overall antiferromagnetic interactions are present in these clusters.
Co-reporter:RichardA. Layfield Dr.;Joseph J.W. McDouall Dr.;ScottA. Sulway;Floriana Tuna Dr.;David Collison ;Richard E.P. Winpenny
Chemistry - A European Journal 2010 Volume 16( Issue 15) pp:4442-4446
Publication Date(Web):
DOI:10.1002/chem.201000158
Co-reporter:Vito Di Noto;Angelika B. Boeer;Sra Lavina;Christopher A. Muryn;Matthias Bauer;Grigore A. Timco;Enrico Negro;Marzio Rancan;Silvia Gross
Advanced Functional Materials 2009 Volume 19( Issue 20) pp:3226-3236
Publication Date(Web):
DOI:10.1002/adfm.200900600
Abstract
The first example of organic–inorganic hybrid materials based on the embedding of a chromium–nickel wheel cluster {[(n-C3H7)2NH2]- [Cr7NiF8(O2C4H5)16]} (Cr7Ni) into poly(methyl methacrylate) (PMMA) and the characterization of the dielectric properties of the obtained material is described. By an optimized copolymerization of the methacrylate-functionalized chromium–nickel wheel with methyl methacrylate in a cluster/monomer 1:200 molar mixture, a homogeneous hybrid material CrNi_MMA200 is obtained. The electrical responses of the non-doped PMMA and of the hybrid material were studied by broadband dielectric spectroscopy (BDS) from 0.01 Hz to 10 MHz and over the temperature range of 5–115 °C. The permittivity profiles reveal two relaxation peaks in the materials, which correspond to the α and β relaxation modes of the PMMA matrix. The position of these modes shifts toward higher frequencies as temperature increases. BDS is a powerful tool revealing the intimate miscibility of the various components of the hybrid material, thus indicating that, on a molecular scale, the material proposed is a homogeneous system. Finally, a value of the dielectric constant of 2.9 at 25 °C and 1 kHz is determined. This value is noticeably lower than the value of 3.2 obtained for pristine PMMA prepared following the same synthesis protocol. Thus, these results classify the hybrid CrNi_MMA200 as an appealing starting material for the development of dielectric polymeric layers for the development of innovative capacitors, transistors, and other microelectronic devices. The vibrational properties of the hybrid materials are investigated by Fourier-transform infrared (FT-IR) and Raman spectroscopy, whereas the thermal behavior is analyzed by thermogravimetric analysis (TGA). Swelling experiments are used to qualitatively evaluate the crosslinking density of the hybrid materials. The integrity of the wheels once embedded in the macromolecular backbone is confirmed by extended X-ray absorption fine structure (EXAFS) and electron spin resonance (EPR) spectroscopic measurements.
Co-reporter:Sumit Khanra, Sanjit Konar, Abraham Clearfield, Madeleine Helliwell, Eric J. L. McInnes, Evangelos Tolis, Floriana Tuna and Richard E. P. Winpenny
Inorganic Chemistry 2009 Volume 48(Issue 12) pp:5338-5349
Publication Date(Web):May 11, 2009
DOI:10.1021/ic9003214
We report the synthesis, structures, and magnetic properties of twelve iron(III) phosphonate cages: [Fe4(μ3-O)Cl(PhCO2)3(PhPO3)3(py)5] 1, [Fe4(μ3-O)(tBuCO2)4(C10H17PO3)3(py)4] 2 (C10H17PO3H2 = camphylphosphonic acid), [Fe7(μ3-O)2(PhPO3)4(MeCO2)9(py)6] 3, [Fe7(μ3-O)2(PhPO3)4(PhCO2)9(py)6] 4, [Fe7(μ3-O)2(tBuPO3)4(tBuCO2)8(py)8](NO3) 5, [Fe7(μ3-O)2(PhPO3)4(MeCO2)8(py)8] 6, [Fe9(μ3-O)2(μ2-OH)(PhPO3)6(tBuCO2)10(MeCN)(H2O)5] 7, [Fe9(μ3-O)2(μ2-OH)(C10H17PO3)6(PhCO2)10(H2O)6] 8, [Fe6(μ3-O)2(O2)(tBuCO2)8(PhPO3)2(H2O)2] 9, [Fe6(μ3-O)2(O2)(tBuCO2)8(C10H17PO3)2(H2O)2] 10, [Fe6(μ3-O)2(O2)(tBuCO2)8(tBuPO3)2(py)2] 11, and [Fe14(μ3-O)4(O2)2(PhPO3)8(tBuCO2)12(H2O)12](NO3)2 12. The results have allowed us to compare the magnetic exchange found with magneto-structural correlations found previously for iron-oxo cages.
Co-reporter:Stuart Langley, Madeleine Helliwell, Roberta Sessoli, Simon J. Teat and Richard E. P. Winpenny
Dalton Transactions 2009 (Issue 16) pp:3102-3110
Publication Date(Web):06 Mar 2009
DOI:10.1039/B819976K
The reaction of cobalt salts with phosphonic acids in the presence of 6-chloro-2-hydroxypyridine as a co-ligand, using sodium methoxide as a base, leads to a series of new polymetallic cobalt cages. Variation of the phosphonate present and the cobalt salt leads to {Co6Na8}, {Co12}, {Co13Na6}, {Co14Na4} and {Co15Na} cages, all of which have been characterized by X-ray crystallography. Using lithium methoxide produces a sixth cage with a {Co6Li9} core. The structures are, in general, extremely irregular with no structural motifs common to the six cages. Magnetic studies of these cages show a general decline in the product χmT with T, but for {Co13Na6}, {Co15Na} and {Co12} there are maxima at low temperature, which suggest non-diamagnetic ground states. Investigation of the dynamic behaviour of the magnetisation of these complexes shows that the {Co13Na6}, and possibly the {Co12} cage, appear to display slow relaxation of magnetisation.
Co-reporter:Sumit Khanra, Madeleine Helliwell, Floriana Tuna, Eric J. L. McInnes and Richard E. P. Winpenny
Dalton Transactions 2009 (Issue 31) pp:6166-6174
Publication Date(Web):19 Jun 2009
DOI:10.1039/B903600H
Four new polymetallic iron(III) phosphonate cages have been made and structurally characterised. These are an octanuclear cage [Fe8O3(OH)2(O2CtBu)11(PhCH2PO3)3(py)3], a decanuclear cage [Fe10O2(OH)8(O2CtBu)10(PhCH2PO3)4(pip)2], a heterometallic cage [Fe6Li5(μ3-O)2(tBuPO3)6(O2CtBu)8(MeOH)2(Py)4] and a tridecanuclear cage [Et3NH]2[Fe13(μ3-O)3(μ2-OH)7(tBuPO3)7(Me3CCO2)14(H2O)] (pip = piperidine, py = pyridine). Magnetic studies of the first three compounds show anti-ferromagnetic exchange between the iron(III) centers leading to diamagnetic ground states for the homometallic cages. For the heterometallic cage, the six Fe(III) centers are arranged in two triangles, and each triangle has an S = 1/2 spin ground state.
Co-reporter:Chin-Fa Lee,
David A. Leigh,
Robin G. Pritchard,
David Schultz,
Simon J. Teat,
Grigore A. Timco
&
Richard E. P. Winpenny
Nature 2009 458(7236) pp:314
Publication Date(Web):2009-03-19
DOI:10.1038/nature07847
The tetravalency of carbon and its ability to form covalent bonds with itself and other elements enables large organic molecules with complex structures, functions and dynamics to be constructed. The varied electronic configurations and bonding patterns of inorganic elements, on the other hand, can impart diverse electronic, magnetic, catalytic and other useful properties to molecular-level structures. Some hybrid organic–inorganic materials that combine features of both chemistries have been developed, most notably metal–organic frameworks1, dense and extended organic–inorganic frameworks2 and coordination polymers3. Metal ions have also been incorporated into molecules that contain interlocked subunits, such as rotaxanes4, 5, 6, 7 and catenanes6, 8, and structures in which many inorganic clusters encircle polymer chains have been described9. Here we report the synthesis of a series of discrete rotaxane molecules in which inorganic and organic structural units are linked together mechanically at the molecular level. Structural units (dialkyammonium groups) in dumb-bell-shaped organic molecules template the assembly of essentially inorganic ‘rings’ about ‘axles’ to form rotaxanes consisting of various numbers of rings and axles. One of the rotaxanes behaves as a ‘molecular shuttle’10: the ring moves between two binding sites on the axle in a large-amplitude motion typical of some synthetic molecular machine systems11, 12, 13, 14, 15. The architecture of the rotaxanes ensures that the electronic, magnetic and paramagnetic characteristics of the inorganic rings—properties that could make them suitable as qubits for quantum computers16, 17, 18—can influence, and potentially be influenced by, the organic portion of the molecule.
Co-reporter:Shoaib Ali, Viswanathan Baskar, Christopher A. Muryn and Richard E. P. Winpenny
Chemical Communications 2008 (Issue 47) pp:6375-6377
Publication Date(Web):04 Nov 2008
DOI:10.1039/B815270E
A new class of oxygen donor ligands is described and preliminary results using these ligands are given which show they can be used to make polymetallic cages.
Co-reporter:Szymon W. Przybylak, Floriana Tuna, Simon J. Teat and Richard E. P. Winpenny
Chemical Communications 2008 (Issue 17) pp:1983-1985
Publication Date(Web):22 Feb 2008
DOI:10.1039/B717277J
Synthetic, structural and magnetic studies of a new Fe(II) single chain magnet are reported.
Co-reporter:Marzio Rancan, Graham N. Newton, Christopher A. Muryn, Robin G. Pritchard, Grigore A. Timco, Leroy Cronin and Richard E. P. Winpenny
Chemical Communications 2008 (Issue 13) pp:1560-1562
Publication Date(Web):20 Feb 2008
DOI:10.1039/B718282A
Synthetic and structural studies of Cr horseshoes are reported which show that these compounds demonstrate a rich supramolecular chemistry through H-bonding interactions, and can act as ligands for metal clusters.
Co-reporter:LarryP. Engelhardt Dr.;ChristopherA. Muryn Dr.;RobinG. Pritchard Dr.;GrigoreA. Timco Dr.;Floriana Tuna Dr.;RichardE.P. Winpenny
Angewandte Chemie International Edition 2008 Volume 47( Issue 5) pp:924-927
Publication Date(Web):
DOI:10.1002/anie.200704132
Co-reporter:RichardE.P. Winpenny
Angewandte Chemie International Edition 2008 Volume 47( Issue 42) pp:7992-7994
Publication Date(Web):
DOI:10.1002/anie.200802742
Co-reporter:GrigoreA. Timco Dr.;EricJ.L. McInnes ;RobinG. Pritchard Dr.;Floriana Tuna Dr. ;RichardE.P. Winpenny
Angewandte Chemie International Edition 2008 Volume 47( Issue 50) pp:9681-9684
Publication Date(Web):
DOI:10.1002/anie.200803637
Co-reporter:RichardE.P. Winpenny
Angewandte Chemie 2008 Volume 120( Issue 42) pp:8112-8114
Publication Date(Web):
DOI:10.1002/ange.200802742
Co-reporter:Barbara A. Breeze, Muralidharan Shanmugam, Floriana Tuna and Richard E. P. Winpenny
Chemical Communications 2007 (Issue 48) pp:5185-5187
Publication Date(Web):19 Oct 2007
DOI:10.1039/B711650K
Three new polymetallic nickel(II) phosphonate complexes are reported; in one cage the twelve nickel centres are arranged at the vertices of a truncated tetrahedron in a similar manner to a Keggin ion.
Co-reporter:E. Carolina Sañudo, Christopher A. Muryn, Madeleine A. Helliwell, Grigore A. Timco, Wolfgang Wernsdorfer and Richard E. P. Winpenny
Chemical Communications 2007 (Issue 8) pp:801-803
Publication Date(Web):23 Nov 2006
DOI:10.1039/B613877B
Cyclic octanuclear complexes, each containing seven group 13 metals and one d-block metal are reported and preliminary physical characterisation of the compounds discussed.
Co-reporter:Marco Affronte, Stefano Carretta, Grigore A. Timco and Richard E. P. Winpenny
Chemical Communications 2007 (Issue 18) pp:1789-1797
Publication Date(Web):02 Feb 2007
DOI:10.1039/B615543J
The synthesis of a series of heterometallic rings and chains is reported. The family is based on the octanuclear cages of general formula [H2NR2][M7M′F8(O2CR′)16], where M is a trivalent metal (Cr, Fe, V, Al, Ga or In), M′ is a divalent metal (Mn, Fe, Co, Ni, Mg, Zn, Cd), R is a linear alkyl chain and O2CR′ is one of around twenty carboxylates. Other members of the family with nonametallic and decametallic cores are described, and some new physics is outlined, including initial investigations of the proposed application of {Cr7Ni} rings as Qubits in quantum information processing.
Co-reporter:E. Carolina Sañudo, Joan Ribas and Richard E. P. Winpenny
New Journal of Chemistry 2007 vol. 31(Issue 8) pp:1421-1423
Publication Date(Web):26 Jun 2007
DOI:10.1039/B704191H
The synthesis of a new pentanuclear V(III) complex [V5O2(Me3CCO2)9Cl2] (1) by solid state methods is described.
Co-reporter:Sumit Khanra Dr.;Marc Kloth Dr.;Hassanatu Mansaray;Christopher A. Muryn Dr.;Floriana Tuna Dr.;E. Carolina Sañudo Dr.;Madeleine Helliwell Dr.;Eric J. L. McInnes ;Richard E. P. Winpenny
Angewandte Chemie 2007 Volume 119(Issue 29) pp:
Publication Date(Web):19 JUN 2007
DOI:10.1002/ange.200701115
Eine ganze Familie: Organophosphonatkomplexe des Vanadiums in hoher Oxidationsstufe sind verbreitet, ihre VIII-Analoga sind dagegen äußerst dünn gesäht. Aus VCl3 und Phosphonaten entsteht unter Solvothermalbedingungen eine ganze Familie entsprechender Vanadium(III)-phosphonate, darunter der schichtförmige Cluster {VIII12(VIVO)} im Bild (V grün, P violett, O rot, C schwarz). Erste Untersuchungen zum magnetischen Verhalten werden ebenfalls beschrieben.
Co-reporter:Sumit Khanra Dr.;Marc Kloth Dr.;Hassanatu Mansaray;Christopher A. Muryn Dr.;Floriana Tuna Dr.;E. Carolina Sañudo Dr.;Madeleine Helliwell Dr.;Eric J. L. McInnes ;Richard E. P. Winpenny
Angewandte Chemie International Edition 2007 Volume 46(Issue 29) pp:
Publication Date(Web):19 JUN 2007
DOI:10.1002/anie.200701115
All in the family: Organophosphonate complexes of high-valent vanadium are common, but their VIII analogues are few and far between. Reaction of VCl3 precursors and phosphonates under solvothermal conditions leads to a family of corresponding vanadium(III)-based phosphonates, including the layered {VIII12(VIVO)} cluster shown in the picture (V green, P purple, O red, C black). Preliminary magnetic studies are also reported.
Co-reporter:Maheswaran Shanmugam, Muralidharan Shanmugam, Guillaume Chastanet, Roberta Sessoli, Talal Mallah, Wolfgang Wernsdorfer and Richard E. P. Winpenny
Journal of Materials Chemistry A 2006 vol. 16(Issue 26) pp:2576-2578
Publication Date(Web):07 Jun 2006
DOI:10.1039/B606571F
Drastic changes in the structure of manganese clusters are observed from a minor modification of a phosphonate ligand.
Co-reporter:Marco Affronte, Filippo Troiani, Alberto Ghirri, Stefano Carretta, Paolo Santini, Valdis Corradini, Raffael Schuecker, Chris Muryn, Grigore Timco and Richard E. Winpenny
Dalton Transactions 2006 (Issue 23) pp:2810-2817
Publication Date(Web):05 May 2006
DOI:10.1039/B515731E
We report on real molecular complexes and propose strategies that explore the possibility of implementation of specific quantum computation architectures with molecular spin systems. We focus on Cr3+ carboxylate derivatives and use the Loss–DiVincenzo scheme as reference.
Co-reporter:Muralidharan Shanmugam;Larry P. Engelhardt;Finn K. Larsen ;Marshall Luban Dr.;Eric J. L. McInnes Dr.;Christopher A. Muryn Dr.;Jacob Overgaard;Eva Rentschler Dr.;Grigore A. Timco Dr.
Chemistry - A European Journal 2006 Volume 12(Issue 32) pp:
Publication Date(Web):29 SEP 2006
DOI:10.1002/chem.200600827
The synthesis, structure, EPR, and magnetic studies of two dodecanuclear heterometallic cyclic clusters are reported. The compounds have the general formula [R2NH2]2[Cr10Cu2F14(O2CCMe3)22] (R=Me, 1 or iPr, 2). Both structures contain an array of metal centers which describe an approximate “hourglass”, with an ammonium cation in the center of each half of the figure. The chromium sites are all six-coordinate, with the two copper sites five-coordinate. The majority of metal–metal edges are bridged by a single fluoride and two pivalate ligands, while two CrCu edges are bridged by a single fluoride and a single pivalate. Magnetic studies show that 1 and 2 exhibit similar (but not identical) behavior, which can be attributed to ten antiferromagnetic and two ferromagnetic exchange interactions around the ring which gives an S=0 ground state. Quantum Monte Carlo calculations have been used to quantify the exchange interactions by successfully simulating the susceptibility for the full temperature range and thus clarifying the distinction between 1 and 2. EPR spectroscopy shows signals due to excited states, and a variable-temperature study has provided an estimate of the energy gap between the first excited state (S=1) and second excited state (S=2) for 1 that is consistent with the value obtained using the QMC method.
Co-reporter:Gopalan Rajaraman, Kirsten E. Christensen, Finn K. Larsen, Grigore A. Timco and R. E. P. Winpenny
Chemical Communications 2005 (Issue 24) pp:3053-3055
Publication Date(Web):06 May 2005
DOI:10.1039/B502115D
A combination of DFT calculations and magnetic studies allow structural features of di- and tetra-nuclear nickel pivalate cage complexes to be deduced.
Co-reporter:Rebecca H. Laye, Finn K. Larsen, Jacob Overgaard, Christopher A. Muryn, Eric J. L. McInnes, Eva Rentschler, Veronica Sanchez, Simon J. Teat, Hans U. Güdel, Oliver Waldmann, Grigore A. Timco and Richard E. P. Winpenny
Chemical Communications 2005 (Issue 9) pp:1125-1127
Publication Date(Web):13 Jan 2005
DOI:10.1039/B416770H
The synthesis and structure of new heterometallic wheels are reported, with preliminary studies of selected compounds.
Co-reporter:Marco Affronte ;Ian Casson;Marco Evangelisti Dr.;Andrea Cini;Stefano Carretta Dr.;Christopher A. Muryn Dr.;Simon J. Teat Dr.;Grigore A. Timco Dr.;Wolfgang Wernsdorfer Dr.
Angewandte Chemie 2005 Volume 117(Issue 40) pp:
Publication Date(Web):13 SEP 2005
DOI:10.1002/ange.200502505
Käfige, aus denen Türen führen: Verknüpfte paramagnetische Käfigkomplexe eignen sich potenziell als Quanten-Gates für die Verarbeitung von Quanteninformationen. In Experimenten konnten achtkernige {Cr7Ni}-Ringe durch organische wie metall-organische Fragmente zu supramolekularen Dimeren verknüpft werden (siehe Struktur; Cr grün, Ni hellgrün, Cu orange, F gelb, O rot, N blau, C schwarz).
Co-reporter:Marco Affronte ;Ian Casson;Marco Evangelisti Dr.;Andrea Cini;Stefano Carretta Dr.;Christopher A. Muryn Dr.;Simon J. Teat Dr.;Grigore A. Timco Dr.;Wolfgang Wernsdorfer Dr.
Angewandte Chemie 2005 Volume 117(Issue 40) pp:
Publication Date(Web):7 OCT 2005
DOI:10.1002/ange.200590133
Co-reporter:Shanmugam Maheswaran;Guillaume Chastanet Dr.;Simon J. Teat Dr.;Talal Mallah ;Roberta Sessoli ;Wolfgang Wernsdorfer Dr.
Angewandte Chemie 2005 Volume 117(Issue 32) pp:
Publication Date(Web):19 JUL 2005
DOI:10.1002/ange.200501265
Riesenspins: Die Strukturen der gemischtvalenten {MnIII20−xMnIIx}-Käfigkomplexe (x=2–6) entsprechen einem Fragment des kubisch-dichtgepackten Gitters (siehe Bild; Mn große Kugeln, O kleine Kugeln). Magnetismusuntersuchungen ergaben für den Käfig mit x=2 bei schwachem Feld einen Grundzustandsspin S von 19±1, der bei stärkeren Feldern auf etwa S=30 steigt. Der Käfig ist ein „Einzelmolekülmagnet“ mit hoher Energiebarriere (43 K) für die Reorientierung der Magnetisierung.
Co-reporter:Shanmugam Maheswaran;Guillaume Chastanet Dr.;Simon J. Teat Dr.;Talal Mallah ;Roberta Sessoli ;Wolfgang Wernsdorfer Dr.
Angewandte Chemie International Edition 2005 Volume 44(Issue 32) pp:
Publication Date(Web):20 JUL 2005
DOI:10.1002/anie.200501265
In a spin: The mixed-valent {MnIII20−xMnIIx} cage complexes (x=2–6) have structures corresponding to a fragment of a cubic close-packed lattice (see picture, Mn large sphere, O small sphere). Magnetic studies show for the cage with x=2 that the ground state has a spin (S) of 19±1 in low field, which increases to about S=30 at higher fields. The cage is a “single molecule magnet” with a high energy barrier (43 K) to reorientation of the magnetization.
Co-reporter:Marco Affronte, Ian Casson, Marco Evangelisti, Andrea Candini, Stefano Carretta, Christopher A. Muryn, Simon J. Teat, Grigore A. Timco, Wolfgang Wernsdorfer,Richard E. P. Winpenny
Angewandte Chemie International Edition 2005 44(40) pp:6496-6500
Publication Date(Web):
DOI:10.1002/anie.200502505
Co-reporter:Marco Affronte, Ian Casson, Marco Evangelisti, Andrea Candini, Stefano Carretta, Christopher A. Muryn, Simon J. Teat, Grigore A. Timco, Wolfgang Wernsdorfer,Richard E. P. Winpenny
Angewandte Chemie International Edition 2005 44(40) pp:6427
Publication Date(Web):
DOI:10.1002/anie.200590133
Co-reporter:Karzan H. Zangana, Eufemio Moreno Pineda, Jürgen Schnack and Richard E. P. Winpenny
Dalton Transactions 2013 - vol. 42(Issue 39) pp:NaN14048-14048
Publication Date(Web):2013/08/22
DOI:10.1039/C3DT52086B
Three octanuclear phosphonate clusters, formulated as [Ln8(O3PtBu)6(μ3-OH)2(H2O)2(HOiBu)(O2CtBu)12](NH3iPr)2 (Ln = Gd, Dy and Tb), were synthesised by refluxing a mixture of pivalic acid (HO2CtBu), Ln(NO3)3·6H2O, tert-Butyl phosphonic acid (H2O3PtBu) and isopropylamine (iPrNH2) in isobutyl alcoholiBuOH.
Co-reporter:Karzan H. Zangana, Eufemio Moreno Pineda, Iñigo J. Vitorica-Yrezabal, Eric J. L. McInnes and Richard E. P. Winpenny
Dalton Transactions 2014 - vol. 43(Issue 35) pp:NaN13249-13249
Publication Date(Web):2014/07/29
DOI:10.1039/C4DT01264J
The preparation and structural characterisation of five 3d–4f mixed metal phosphonate cages with general formula [CrIII6LnIII2(μ3-O)2(H2O)2(O3PtBu)4(O2CtBu)12(HOiBu)2(iPrNH2)2] where LnIII = La, 1; Tb, 3; Dy, 4; Ho, 5 and [CrIII6GdIII2(μ3-O)2(H2O)2(O3PtBu)4(O2CtBu)12(HOiBu)4] (2) are reported. The structure contains two oxo-centred {Cr3} triangles, bridged by phosphonates and lanthanides. The magnetic behaviour of 1 has been modelled as two non-interacting isosceles triangles, involving two antiferromagnetic interactions (J1 = −8.8 cm−1) with a smaller ferromagnetic interaction for the unique edge of the triangle (J2 = +1.3 cm−1) giving an isolated S = 3/2 ground state per triangle. The quartet ground state has been proven through simulation of electron paramagnetic resonance (EPR) spectra obtained at the X- and Q-band. EPR simulations have also resulted in the introduction of small single-ion Zero Field Splitting (ZFS) parameters D = ±0.19 cm−1 and rhombic term E = ±0.02 cm−1, which are consistent with strong exchange limit calculations for an isolated S = 3/2 (D = ±0.22 and E = ±0.018 cm−1).
Co-reporter:Yan-Zhen Zheng, Barbara A. Breeze, Grigore A. Timco, Floriana Tuna and Richard E. P. Winpenny
Dalton Transactions 2010 - vol. 39(Issue 27) pp:NaN6177-6177
Publication Date(Web):2010/06/07
DOI:10.1039/C0DT00017E
Two new Co(II)–Cr(III) phosphonate clusters with [CoII4CrIII4] and [CoII8CrIII4] cores have been synthesized by a displacement reaction from a pre-formed heterometallic carboxylate cage. Magnetic studies show overall antiferromagnetic interactions are present in these clusters.
Co-reporter:Thomas B. Faust, Floriana Tuna, Grigore A. Timco, Marco Affronte, Valerio Bellini, Wolfgang Wernsdorfer and Richard E. P. Winpenny
Dalton Transactions 2012 - vol. 41(Issue 44) pp:NaN13631-13631
Publication Date(Web):2012/06/21
DOI:10.1039/C2DT31292A
A series of heteroaromatic bridging ligands are employed in the synthesis of a family of paramagnetic, heterometallic ring dimers. The extent of spin propagation between the rings via the organic conduit is investigated through micro-SQUID magnetometry and EPR spectroscopy from which conclusions over the mechanism of spin-communication are drawn.
Co-reporter:Shoaib Ali, Viswanathan Baskar, Christopher A. Muryn and Richard E. P. Winpenny
Chemical Communications 2008(Issue 47) pp:NaN6377-6377
Publication Date(Web):2008/11/04
DOI:10.1039/B815270E
A new class of oxygen donor ligands is described and preliminary results using these ligands are given which show they can be used to make polymetallic cages.
Co-reporter:Grigore A. Timco, Eric J. L. McInnes and Richard E. P. Winpenny
Chemical Society Reviews 2013 - vol. 42(Issue 4) pp:NaN1806-1806
Publication Date(Web):2012/09/18
DOI:10.1039/C2CS35232J
Heterometallic rings of general formula [Cat][M7M′F8(O2CtBu)8] (M = a trivalent metal, M′ = a divalent metal, cat = a secondary ammonium cation, caesium or rubidium) contain an octagon of metal centres with each metal–metal edge bridged by a fluoride and two carboxylates. The rings when M = CrIII give remarkably beautiful EPR and INS spectra, and allow us to examine new techniques. Use of these techniques allows us to study the models used to describe magnetic behaviour in exchange coupled systems. In this tutorial review we discuss the two main approaches to modelling magnetic data – the strong exchange limit and the microscopic Hamiltonian approaches, aiming to explain the major differences between the two approaches. We also describe some more esoteric measurements and theories.
Co-reporter:Andrew McRobbie, Asad R. Sarwar, Steven Yeninas, Harriott Nowell, Michael L. Baker, David Allan, Marshall Luban, Christopher A. Muryn, Robin G. Pritchard, Ruslan Prozorov, Grigore A. Timco, Floriana Tuna, George F. S. Whitehead and Richard E. P. Winpenny
Chemical Communications 2011 - vol. 47(Issue 22) pp:NaN6253-6253
Publication Date(Web):2011/05/06
DOI:10.1039/C1CC11516B
Hexametallic chromium(III) chains can act as fluoride donor ligands to lanthanide ions giving {(Cr6)Lnx}n complexes; preliminary spectroscopic studies are reported.
Co-reporter:Yan-Zhen Zheng, Marco Evangelisti and Richard E. P. Winpenny
Chemical Science (2010-Present) 2011 - vol. 2(Issue 1) pp:NaN102-102
Publication Date(Web):2010/09/24
DOI:10.1039/C0SC00371A
Three 3d–4f phosphonate complexes, [CoII8GdIII8(μ3-OH)4(NO3)4(O3PtBu)8(O2CtBu)16], [CoII8GdIII4(O3PtBu)6(O2CtBu)16] and [CoII4GdIII6(O3PCH2Ph)6(O2CtBu)14(MeCN)2], have been synthesized and have structures that can be related to molecular grids. Magnetic studies show they have promise as low temperature magnetic refrigerants.
Co-reporter:Shoaib Ali, Christopher A. Muryn, Floriana Tuna and Richard E. P. Winpenny
Dalton Transactions 2010 - vol. 39(Issue 40) pp:NaN9597-9597
Publication Date(Web):2010/09/03
DOI:10.1039/C0DT00482K
The polynucleating oxygen donor ligands, [(SbAr)4O2(PhPO3H)4(PhPO3)4] 1 and [(SbAr)2O(HO3PtBu)6] 2, based on condensation of p-chlorophenylstibonic acid (ArSbO3H2) and phosphonic acids, were used to prepare polymetallic cobalt(II) complexes. Reaction of 1 with cobalt acetate under solvothermal conditions produces three different types of polymetallic cobalt complexes. With LiOMe/pyridine as base in MeOH a dinuclear cobalt cage, [Co2(SbAr)4O4(O3PPh)4(OMe)4py2] 3, is formed, with four Sb(II) and two Co(II) centres bridged by μ3-oxides and phosphonates. The pyridine in the structure can be replaced by 3-picoline 4, 4-picoline 5, quinoline 6, 1,2-diazole 7, 4-phenylpyridine 8, 4-ethyl pyridine 9 and methanol 10. Using pyrazine (pyz) instead of pyridine under the same conditions a polymer, [Co2(SbAr)4O4(O3PPh)4(OMe)4(C4H4N2)]n11, is formed. A similar 1D-polymer forms with 4,4′-bipyridyl-ethylene 12 in place of pyrazine. With Et3N/pyridine as base in MeCN a tetranuclear cobalt cage, [Co4(SbAr)5O9(O3PPh)6(py)4] 13, with five Sb(II) centres forming a “bowtie” and bridging to four Co(II) centres by phosphonates and μ3-oxides, is formed. The reaction of 2 with cobalt acetate using LiOMe/pyridine as base in methanol, under solvothermal conditions, produces a dinuclear Co(II) complex, [Co2(SbAr)2(O3PtBu)3O2(OMe)2(py)2] 14, with two CoII and two Sb centres at the vertices of a distorted tetrahedron. Magnetic measurements on selected number of these cobalt cages are reported.
Co-reporter:Karzan H. Zangana, Eufemio Moreno Pineda and Richard E. P. Winpenny
Dalton Transactions 2015 - vol. 44(Issue 28) pp:NaN12525-12525
Publication Date(Web):2015/06/10
DOI:10.1039/C5DT01786F
Two new tetrametallic lanthanide-phosphonate complexes have been structurally and magnetically characterised. The {Dy4} complex is a single molecule magnet.
Co-reporter:George F. S. Whitehead, Simon J. Teat, Kevin J. Gagnon, Grigore A. Timco and Richard E. P. Winpenny
Chemical Communications 2015 - vol. 51(Issue 17) pp:NaN3536-3536
Publication Date(Web):2015/02/03
DOI:10.1039/C4CC10035B
We present the first example of an extended 3D framework synthesised without the use of an isolable organic component. This is achieved by the combination of two cage complexes isolated and functionalised prior to synthesis; [nPr2NH2][Cr7NiF8(O2CtBu)14(O2CC5H4N)2] and [Fe2CoO(O2CtBu)6(HO2CtBu)3], where the former is as a bidentate linker, bridging between three nodes of the latter.
Co-reporter:George F. S. Whitehead, Bryony Cross, Laura Carthy, Victoria A. Milway, Harapriya Rath, Antonio Fernandez, Sarah L. Heath, Christopher A. Muryn, Robin G. Pritchard, Simon J. Teat, Grigore A. Timco and Richard E. P. Winpenny
Chemical Communications 2013 - vol. 49(Issue 65) pp:NaN7197-7197
Publication Date(Web):2013/06/20
DOI:10.1039/C3CC42300J
Coordination polymers and metal–organic rotaxane frameworks are reported where the organic linker is replaced by functionalised inorganic clusters that act as bridging ligands.
Co-reporter:Karzan H. Zangana, Eufemio Moreno Pineda, Eric J. L. McInnes, Jürgen Schnack and Richard E. P. Winpenny
Chemical Communications 2014 - vol. 50(Issue 12) pp:NaN1440-1440
Publication Date(Web):2013/12/20
DOI:10.1039/C3CC48708C
Two {Ln10} cages are reported (Ln = Dy or Gd) which feature a nine-metal ring surrounding a central metal site. Magnetic studies show weak anti-ferromagnetic exchange around the nine-metal ring, which should create spin frustration.
Co-reporter:Robin J. Blagg, Floriana Tuna, Eric J. L. McInnes and Richard E. P. Winpenny
Chemical Communications 2011 - vol. 47(Issue 38) pp:NaN10589-10589
Publication Date(Web):2011/09/01
DOI:10.1039/C1CC14186D
Pentametallic Ln complexes of formula [Ln5O(OiPr)13] have been made, where LnIII = Sm, Gd, Tb, Ho and Er; slow magnetisation relaxation to 33 K is observed for the Ho complex with an energy barrier of ca. 400 K.
Co-reporter:Scott A. Sulway, Richard A. Layfield, Floriana Tuna, Wolfgang Wernsdorfer and Richard E. P. Winpenny
Chemical Communications 2012 - vol. 48(Issue 10) pp:NaN1510-1510
Publication Date(Web):2011/09/16
DOI:10.1039/C1CC14643B
[Cp2Dy(thf)(μ-Cl)]2 (2) was synthesized from [Cp2Dy(μ-Cl)]n, which crystalizes as two polymorphs, with n = 2 (1a) or ∞ (1b). All three compounds show slow relaxation of magnetization, and in 2 the quantum tunnelling was found to be exchange-biased.
Co-reporter:Karzan H. Zangana, Eufemio Moreno Pineda and Richard E. P. Winpenny
Dalton Transactions 2014 - vol. 43(Issue 45) pp:NaN17107-17107
Publication Date(Web):2014/10/13
DOI:10.1039/C4DT02630F
The synthesis, structures and magnetic properties of a family of lanthanide complexes containing phosphonate ligands are reported. Reaction of hydrated lanthanide nitrate and tbutylphosphonic acid under reflux conditions in iso-butanol, in the presence of pivalic acid as a co-ligand produced five new lanthanide complexes; pyridine (py) was present as a base. The compounds formed are tetrametallic, with the general formula [pyH]4[Ln4(μ3-OH)(O3PtBu)3(HO3PtBu)(O2CtBu)2(NO3)6] where Ln = GdIII, 1; TbIII, 2; DyIII, 3; HoIII, 4 and ErIII, 5. The metal sites within the complexes lie on the vertices of a triangle-based pyramid, with phosphonate ligands on the triangular faces linking the apical Ln site to the Ln sites in the base. Each lanthanide(III) site is eight-coordinate. Magnetic studies of the compounds show a decline in the product χMT with T; modelling the behaviour of 1 shows anti-ferromagnetic exchange between GdIII centres within the triangle with a negligible interaction to the fourth GdIII centre at the apex of the trigonal pyramid.
Co-reporter:Harapriya Rath, Grigore A. Timco, Valdis Corradini, Alberto Ghirri, Umberto del Pennino, Antonio Fernandez, Robin G. Pritchard, Christopher A. Muryn, Marco Affronte and Richard E. P. Winpenny
Chemical Communications 2013 - vol. 49(Issue 33) pp:NaN3406-3406
Publication Date(Web):2013/03/19
DOI:10.1039/C3CC38699F
Hybrid organic–inorganic [2]- and [3]rotaxanes have been synthesised, and their ability to bind to Au surfaces studied; the length of the tethering group is found to control how the supramolecular assembly binds to the surface and we find that [2]rotaxanes show improved stability over previous studies of simple inorganic rings.
Co-reporter:E. Carolina Sañudo, Christopher A. Muryn, Madeleine A. Helliwell, Grigore A. Timco, Wolfgang Wernsdorfer and Richard E. P. Winpenny
Chemical Communications 2007(Issue 8) pp:NaN803-803
Publication Date(Web):2006/11/23
DOI:10.1039/B613877B
Cyclic octanuclear complexes, each containing seven group 13 metals and one d-block metal are reported and preliminary physical characterisation of the compounds discussed.
Co-reporter:Stuart Langley, Madeleine Helliwell, Roberta Sessoli, Simon J. Teat and Richard E. P. Winpenny
Dalton Transactions 2009(Issue 16) pp:NaN3110-3110
Publication Date(Web):2009/03/06
DOI:10.1039/B819976K
The reaction of cobalt salts with phosphonic acids in the presence of 6-chloro-2-hydroxypyridine as a co-ligand, using sodium methoxide as a base, leads to a series of new polymetallic cobalt cages. Variation of the phosphonate present and the cobalt salt leads to {Co6Na8}, {Co12}, {Co13Na6}, {Co14Na4} and {Co15Na} cages, all of which have been characterized by X-ray crystallography. Using lithium methoxide produces a sixth cage with a {Co6Li9} core. The structures are, in general, extremely irregular with no structural motifs common to the six cages. Magnetic studies of these cages show a general decline in the product χmT with T, but for {Co13Na6}, {Co15Na} and {Co12} there are maxima at low temperature, which suggest non-diamagnetic ground states. Investigation of the dynamic behaviour of the magnetisation of these complexes shows that the {Co13Na6}, and possibly the {Co12} cage, appear to display slow relaxation of magnetisation.
Co-reporter:Barbara A. Breeze, Muralidharan Shanmugam, Floriana Tuna and Richard E. P. Winpenny
Chemical Communications 2007(Issue 48) pp:NaN5187-5187
Publication Date(Web):2007/10/19
DOI:10.1039/B711650K
Three new polymetallic nickel(II) phosphonate complexes are reported; in one cage the twelve nickel centres are arranged at the vertices of a truncated tetrahedron in a similar manner to a Keggin ion.
Co-reporter:Grigore Timco, Simone Marocchi, Elena Garlatti, Claire Barker, Morten Albring, Valerio Bellini, Franca Manghi, Eric J. L. McInnes, Robin G. Pritchard, Floriana Tuna, Wolfgang Wernsdorfer, Giulia Lorusso, Giuseppe Amoretti, Stefano Carretta, Marco Affronte and Richard E. P. Winpenny
Dalton Transactions 2016 - vol. 45(Issue 42) pp:NaN16615-16615
Publication Date(Web):2016/07/21
DOI:10.1039/C6DT01941B
Nine new complexes are reported involving linked heterometallic rings; one ring is designed as a ligand for the second, and the compounds produced can be regarded as molecular prototypes for implementing quantum gates featuring two subtly different qubits.
Co-reporter:Szymon W. Przybylak, Floriana Tuna, Simon J. Teat and Richard E. P. Winpenny
Chemical Communications 2008(Issue 17) pp:NaN1985-1985
Publication Date(Web):2008/02/22
DOI:10.1039/B717277J
Synthetic, structural and magnetic studies of a new Fe(II) single chain magnet are reported.
Co-reporter:Michael L. Baker, Stergios Piligkos, Alberto Bianchi, Stefano Carretta, David Collison, Joseph J. W. McDouall, Eric J. L. McInnes, Hannu Mutka, Grigore A. Timco, Floriana Tuna, Prabha Vadivelu, Høgni Weihe, Hans U. Güdel and Richard E. P. Winpenny
Dalton Transactions 2011 - vol. 40(Issue 34) pp:NaN8539-8539
Publication Date(Web):2011/07/05
DOI:10.1039/C1DT10547G
An investigation into the physical consequences of including a Jahn–Teller distorted CuII ion within an antiferromagnetically coupled ring, [R2NH2][Cr7CuF8((O2CtBu)16)] is reported. Inelastic neutron scattering (INS) and electron paramagnetic resonance (EPR) spectroscopic data are simulated using a microscopic spin Hamiltonian, and show that the two Cr–Cu exchange interactions must be inequivalent. One Cr–Cu exchange is found to be antiferromagnetic and the other ferromagnetic. The geometry of the Jahn–Teller elongation is deduced from these results, and shows that a Jahn–Teller elongation axis must lie in the plane of the Cr7Cu wheel; the elongation is not observed by X-ray crystallography, due to positional disorder of the Cu site within the wheel. An electronic structure calculation confirms the structural distortion of the Cu site.
Co-reporter:Marzio Rancan, Graham N. Newton, Christopher A. Muryn, Robin G. Pritchard, Grigore A. Timco, Leroy Cronin and Richard E. P. Winpenny
Chemical Communications 2008(Issue 13) pp:NaN1562-1562
Publication Date(Web):2008/02/20
DOI:10.1039/B718282A
Synthetic and structural studies of Cr horseshoes are reported which show that these compounds demonstrate a rich supramolecular chemistry through H-bonding interactions, and can act as ligands for metal clusters.
Co-reporter:Sumit Khanra, Madeleine Helliwell, Floriana Tuna, Eric J. L. McInnes and Richard E. P. Winpenny
Dalton Transactions 2009(Issue 31) pp:NaN6174-6174
Publication Date(Web):2009/06/19
DOI:10.1039/B903600H
Four new polymetallic iron(III) phosphonate cages have been made and structurally characterised. These are an octanuclear cage [Fe8O3(OH)2(O2CtBu)11(PhCH2PO3)3(py)3], a decanuclear cage [Fe10O2(OH)8(O2CtBu)10(PhCH2PO3)4(pip)2], a heterometallic cage [Fe6Li5(μ3-O)2(tBuPO3)6(O2CtBu)8(MeOH)2(Py)4] and a tridecanuclear cage [Et3NH]2[Fe13(μ3-O)3(μ2-OH)7(tBuPO3)7(Me3CCO2)14(H2O)] (pip = piperidine, py = pyridine). Magnetic studies of the first three compounds show anti-ferromagnetic exchange between the iron(III) centers leading to diamagnetic ground states for the homometallic cages. For the heterometallic cage, the six Fe(III) centers are arranged in two triangles, and each triangle has an S = 1/2 spin ground state.
Co-reporter:Marco Affronte, Stefano Carretta, Grigore A. Timco and Richard E. P. Winpenny
Chemical Communications 2007(Issue 18) pp:NaN1797-1797
Publication Date(Web):2007/02/02
DOI:10.1039/B615543J
The synthesis of a series of heterometallic rings and chains is reported. The family is based on the octanuclear cages of general formula [H2NR2][M7M′F8(O2CR′)16], where M is a trivalent metal (Cr, Fe, V, Al, Ga or In), M′ is a divalent metal (Mn, Fe, Co, Ni, Mg, Zn, Cd), R is a linear alkyl chain and O2CR′ is one of around twenty carboxylates. Other members of the family with nonametallic and decametallic cores are described, and some new physics is outlined, including initial investigations of the proposed application of {Cr7Ni} rings as Qubits in quantum information processing.
Co-reporter:Antonio Fernandez, Eufemio Moreno Pineda, Jesùs Ferrando-Soria, Eric J. L. McInnes, Grigore A. Timco and Richard E. P. Winpenny
Chemical Communications 2015 - vol. 51(Issue 55) pp:NaN11129-11129
Publication Date(Web):2015/06/15
DOI:10.1039/C5CC02216A
A hybrid organic–inorganic molecular daisy chain has been synthesised in one pot reaction. The molecule contains two {Cr6Zn2} rings linked through an organic molecule that acts as both template and ligand. Magnetic and spectroscopic data reveal the magnetic complexity of the daisy chain, which can be casted to two magnetic isomers through comparison of experimental and simulated data for Cr(III) chains.
Co-reporter:George F. S. Whitehead, Jesús Ferrando-Soria, Laura Carthy, Robin G. Pritchard, Simon J. Teat, Grigore A. Timco and Richard E. P. Winpenny
Dalton Transactions 2016 - vol. 45(Issue 4) pp:NaN1647-1647
Publication Date(Web):2015/12/22
DOI:10.1039/C5DT04062K
Here we present a series of linked cage complexes of functionalised variants of the octametallic ring {Cr7Ni} with the general formula [nPr2NH2][Cr7NiF8(O2CtBu)15(O2CR)], where HO2CR is a N-heterocycle containing carboxylic acid. These compounds are made by reacting [nPr2NH2][Cr7NiF8(O2CtBu)15(O2CR)] with a variety of simple metal salts and metal dimers. The carboxylic acids studied include iso-nicotinic acid, 3-(4-pyridyl)acrylic acid and 4-pyridazine carboxylic acid. These new linked cage complexes have been studied structurally and the study highlights the versatility of functionalised {Cr7Ni} as a Lewis base ligand. As {Cr7Ni} is a putative molecular electron spin qubit this work contributes to our understanding of the chemistry that might be required to assemble molecular spin qubits.
Co-reporter:Shoaib Ali, Christopher A. Muryn, Floriana Tuna and Richard E. P. Winpenny
Dalton Transactions 2010 - vol. 39(Issue 1) pp:NaN131-131
Publication Date(Web):2009/11/20
DOI:10.1039/B913467K
A polynucleating oxygen donor ligand based on condensation of p-chlorophenylstibonic acid (ArSbO3H2) and t-butylphosphonic acid is reported. [(SbAr)2O(HO3PtBu)6] contains two antimony centres, bridged by an oxide and two hydrogen phosphonates. Reaction with copper acetate under solvothermal conditions produces four new polymetallic copper complexes. With pyridine used as a base the major product is a tetracopper cage, [Cu4O2(SbAr)2(O3PtBu)2(O2CMe)2(OMe)6], with the four copper centres arranged in a rhombus; a minor product is a tricopper complex, [Cu3O4(SbAr)2(O3PtBu)4(py)3]. With LiOMe as base the major product is again the tetranuclear cage, but the minor product is a heterometallic cage, [Cu5Li4O6(SbAr)4(O3PtBu)6(O2CMe)2(OMe)4 (MeOH)4]. With 2,6-lutidine as base an octametallic complex is formed, [Cu8O4(SbAr)2(O3PtBu)6(O2CMe)4(lutidine)2]. Magnetic studies show both anti-ferromagnetic and weak ferromagnetic exchange between the copper centres in these new complexes.
Co-reporter:Matthew Gregson, Nicholas F. Chilton, Ana-Maria Ariciu, Floriana Tuna, Iain F. Crowe, William Lewis, Alexander J. Blake, David Collison, Eric J. L. McInnes, Richard E. P. Winpenny and Stephen T. Liddle
Chemical Science (2010-Present) 2016 - vol. 7(Issue 1) pp:NaN165-165
Publication Date(Web):2015/11/23
DOI:10.1039/C5SC03111G
We report a dysprosium(III) bis(methanediide) single molecule magnet (SMM) where stabilisation of the highly magnetic states and suppression of mixing of opposite magnetic projections is imposed by a linear arrangement of negatively-charged donor atoms supported by weak neutral donors. Treatment of [Ln(BIPMTMS)(BIPMTMSH)] [Ln = Dy, 1Dy; Y, 1Y; BIPMTMS = {C(PPh2NSiMe3)2}2−; BIPMTMSH = {HC(PPh2NSiMe3)2}−] with benzyl potassium/18-crown-6 ether (18C6) in THF afforded [Ln(BIPMTMS)2][K(18C6)(THF)2] [Ln = Dy, 2Dy; Y, 2Y]. AC magnetic measurements of 2Dy in zero DC field show temperature- and frequency-dependent SMM behaviour. Orbach relaxation dominates at high temperature, but at lower temperatures a second-order Raman process dominates. Complex 2Dy exhibits two thermally activated energy barriers (Ueff) of 721 and 813 K, the largest Ueff values for any monometallic dysprosium(III) complex. Dilution experiments confirm the molecular origin of this phenomenon. Complex 2Dy has rich magnetic dynamics; field-cooled (FC)/zero-field cooled (ZFC) susceptibility measurements show a clear divergence at 16 K, meaning the magnetic observables are out-of-equilibrium below this temperature, however the maximum in ZFC, which conventionally defines the blocking temperature, TB, is found at 10 K. Magnetic hysteresis is also observed in 10% 2Dy@2Y at these temperatures. Ab initio calculations suggest the lowest three Kramers doublets of the ground 6H15/2 multiplet of 2Dy are essentially pure, well-isolated |±15/2〉, |±13/2〉 and |±11/2〉 states quantised along the CDyC axis. Thermal relaxation occurs via the 4th and 5th doublets, verified experimentally for the first time, and calculated Ueff values of 742 and 810 K compare very well to experimental magnetism and luminescence data. This work validates a design strategy towards realising high-temperature SMMs and produces unusual spin relaxation behaviour where the magnetic observables are out-of-equilibrium some 6 K above the formal blocking temperature.
Co-reporter:Eufemio Moreno Pineda, Giulia Lorusso, Karzan H. Zangana, Elias Palacios, Jürgen Schnack, Marco Evangelisti, Richard E. P. Winpenny and Eric J. L. McInnes
Chemical Science (2010-Present) 2016 - vol. 7(Issue 8) pp:NaN4895-4895
Publication Date(Web):2016/04/25
DOI:10.1039/C6SC01415A
We report the synthesis and structure of a molecular {Gd7} cage of the formula (iPr2NH2)6[Gd7(μ3-OH)3(CO3)6(O2CtBu)12] which has crystallographic C3h symmetry. Low temperature specific heat and adiabatic demagnetization experiments (the latter achieving temperatures below 100 mK), lead to the observation of the effects of both intramolecular dipolar interactions and geometric spin frustration. The dipolar interaction leads to a massive rearrangement of energy levels such that specific heat and entropy below 2 K are strongly modified while magnetic susceptibility and magnetization above 2 K are not affected. The consequences of these phenomena for low temperature magnetocaloric applications are discussed.
Co-reporter:Kandasamy Gopal, Floriana Tuna and Richard E. P. Winpenny
Dalton Transactions 2011 - vol. 40(Issue 45) pp:NaN12047-12047
Publication Date(Web):2011/09/07
DOI:10.1039/C1DT10855G
Two new iron(III)-potassium phosphonate cage complexes with {K2Fe6} and {K2Fe4} cores are reported. Magnetic studies reveal antiferromagnetic interactions between the Fe(III) centres occur in these cages.
Co-reporter:Grigore A. Timco, Thomas B. Faust, Floriana Tuna and Richard E. P. Winpenny
Chemical Society Reviews 2011 - vol. 40(Issue 6) pp:NaN3075-3075
Publication Date(Web):2011/01/17
DOI:10.1039/C0CS00151A
Linking polymetallic cages can be a method for creating new structures and new properties. In this tutorial review we use heterometallic anti-ferromagnetically coupled rings (AF-rings) as exemplars for three approaches that can be used to link cage compounds. The first of three routes involves an ion-pair interaction supported by hydrogen-bonding interactions, which allows the synthesis of hybrid rotaxanes among other materials. The second route involves functionalising the exterior of the AF-ring so that it will act as a Lewis base; complexes involving coordination of pyridine to bridging monometallic and dimetallic fragments are discussed. The third route involves creating a vacancy on one site of the AF-ring, and then using the ring as a Lewis acid. Di-imine ligands can then be used to link the AF-rings into dimers. A brief discussion of the physical properties of these systems is also included.
Co-reporter:Thomas B. Faust, Paul G. Heath, Christopher A. Muryn, Grigore A. Timco and Richard E. P. Winpenny
Chemical Communications 2010 - vol. 46(Issue 34) pp:NaN6260-6260
Publication Date(Web):2010/08/09
DOI:10.1039/C0CC01188F
A fluoro-metallocrown selectively binds caesium, extracting it from aqueous solutions into an organic layer; the binding of Cs is monitored by 1H-NMR of the paramagnetic complexes.
Co-reporter:Viswanathan Baskar, Kandasamy Gopal, Madeleine Helliwell, Floriana Tuna, Wolfgang Wernsdorfer and Richard E. P. Winpenny
Dalton Transactions 2010 - vol. 39(Issue 20) pp:NaN4750-4750
Publication Date(Web):2010/04/12
DOI:10.1039/B927114G
Three new Cu–Ln cage complexes bridged by phosphonates and acetates are reported; one—a Cu24Dy8 cage—is a new single molecule magnet (SMM).
Co-reporter:Ze-Min Zhang, Karzan H. Zangana, Andreas K. Kostopoulos, Ming-Liang Tong and Richard E. P. Winpenny
Dalton Transactions 2016 - vol. 45(Issue 22) pp:NaN9044-9044
Publication Date(Web):2016/05/10
DOI:10.1039/C6DT00876C
Reaction of (aminomethyl)phosphonic acid (ampH2) with a mixture of gadolinium and cobalt pivalates under solvothermal conditions, led to a pseudo-icosahedral cage {Gd12}, which shows a large magnetocaloric effect (MCE).
Co-reporter:George F. S. Whitehead, Jesùs Ferrando-Soria, Lorna G. Christie, Nicholas F. Chilton, Grigore A. Timco, Fabrizio Moro and Richard E. P. Winpenny
Chemical Science (2010-Present) 2014 - vol. 5(Issue 1) pp:NaN239-239
Publication Date(Web):2013/10/22
DOI:10.1039/C3SC52095A
The synthesis, structures and magnetism of a new nano-scale constructs using carboxylic acid functionalised {Cr7Ni} rings are reported. Well-established carboxylate chemistry is used to synthesise of spectacular assemblies including a {Zn4O} tetrahedron surrounded by an octahedron of {Cr7Ni} rings.
Co-reporter:Nicholas F. Chilton, Conrad A. P. Goodwin, David P. Mills and Richard E. P. Winpenny
Chemical Communications 2015 - vol. 51(Issue 1) pp:NaN103-103
Publication Date(Web):2014/11/05
DOI:10.1039/C4CC08312A
We report the first near-linear bis(amide) 4f-block compound and show that this novel structure, if implemented with dysprosium(III), would have unprecedented single molecule magnet (SMM) properties with an energy barrier, Ueff, for reorientation of magnetization of 1800 cm−1.
![Poly[thio(methyl-1,2-ethanediyl)]](http://img.cochemist.com/ccimg/9100/9064-17-9.png)
![Poly[thio(methyl-1,2-ethanediyl)]](http://img.cochemist.com/ccimg/9100/9064-17-9_b.png)
![Methanone, bis[2-(methylthio)-4-pyrimidinyl]-](http://img.cochemist.com/ccimg/388600/388573-29-3.png)
![Methanone, bis[2-(methylthio)-4-pyrimidinyl]-](http://img.cochemist.com/ccimg/388600/388573-29-3_b.png)
![5H-Benzo[a]phenoxazin-5-one,9-(diethylamino)-](http://img.cochemist.com/ccimg/7400/7385-67-3.png)
![5H-Benzo[a]phenoxazin-5-one,9-(diethylamino)-](http://img.cochemist.com/ccimg/7400/7385-67-3_b.png)
