Eric J. L. McInnes

Rationalization of Anomalous Pseudocontact Shifts and Their Solvent Dependence in a Series of C3-Symmetric Lanthanide Complexes

Co-reporter:Michele Vonci, Kevin Mason, Elizaveta A. Suturina, Andrew T. Frawley, Steven G. Worswick, Ilya Kuprov, David Parker, Eric J. L. McInnes, and Nicholas F. Chilton

Journal of the American Chemical Society October 11, 2017 Volume 139(Issue 40) pp:14166-14166

Publication Date(Web):September 8, 2017

DOI:10.1021/jacs.7b07094

Bleaney’s long-standing theory of magnetic anisotropy has been employed with some success for many decades to explain paramagnetic NMR pseudocontact shifts, and has been the subject of many subsequent approximations. Here, we present a detailed experimental and theoretical investigation accounting for the anomalous solvent dependence of NMR shifts for a series of lanthanide(III) complexes, namely [LnL1] (Ln = Eu, Tb, Dy, Ho, Er, Tm, and Yb; L1: 1,4,7-tris[(6-carboxypyridin-2-yl)methyl]-1,4,7-triazacyclononane), taking into account the effect of subtle ligand flexibility on the electronic structure. We show that the anisotropy of the room temperature magnetic susceptibility tensor, which in turn affects the sign and magnitude of the pseudocontact chemical shift, is extremely sensitive to minimal structural changes in the first coordination sphere of L1. We show that DFT structural optimizations do not give accurate structural models, as assessed by the experimental chemical shifts, and thus we determine a magnetostructural correlation and employ this to evaluate the accurate solution structure for each [LnL1]. This approach allows us to explain the counterintuitive pseudocontact shift behavior, as well as a striking solvent dependence. These results have important consequences for the analysis and design of novel magnetic resonance shift and optical emission probes that are sensitive to the local solution environment and polarity.

[MIII2MII3]n+ trigonal bipyramidal cages based on diamagnetic and paramagnetic metalloligands

Co-reporter:S. Sanz;H. M. O'Connor;V. Martí-Centelles;P. Comar;M. B. Pitak;S. J. Coles;G. Lorusso;E. Palacios;M. Evangelisti;A. Baldansuren;N. F. Chilton;H. Weihe;E. J. L. McInnes;P. J. Lusby;S. Piligkos;E. K. Brechin

Chemical Science (2010-Present) 2017 vol. 8(Issue 8) pp:5526-5535

Publication Date(Web):2017/07/24

DOI:10.1039/C7SC00487G

A family of five [MIII2MII3]n+ trigonal bipyramidal cages (MIII = Fe, Cr and Al; MII = Co, Zn and Pd; n = 0 for 1–3 and n = 6 for 4–5) of formulae [Fe2Co3L6Cl6] (1), [Fe2Zn3L6Br6] (2), [Cr2Zn3L6Br6] (3), [Cr2Pd3L6(dppp)3](OTf)6 (4) and [Al2Pd3L6(dppp)3](OTf)6 (5) (where HL is 1-(4-pyridyl)butane-1,3-dione and dppp is 1,3-bis(diphenylphosphino)propane) are reported. Neutral cages 1–3 were synthesised using the tritopic [MIIIL3] metalloligand in combination with the salts CoIICl2 and ZnIIBr2, which both act as tetrahedral linkers. The assembly of the cis-protected [PdII(dppp)(OTf)2] with [MIIIL3] afforded the anionic cages 4–5 of general formula [MIII2PdII3](OTf)6. The metallic skeleton of all cages describes a trigonal bipyramid with the MIII ions occupying the two axial sites and the MII ions sitting in the three equatorial positions. Direct current (DC) magnetic susceptibility, magnetisation and heat capacity measurements on 1 reveal weak antiferromagnetic exchange between the FeIII and CoII ions. EPR spectroscopy demonstrates that the distortion imposed on the {MO6} coordination sphere of [MIIIL3] by complexation in the {MIII2MII3} supramolecules results in a small, but measurable, increase of the zero field splitting at MIII. Complete active space self-consistent field (CASSCF) calculations on the three unique CoII sites of 1 suggest DCo ≈ −14 cm−1 and E/D ≈ 0.1, consistent with the magnetothermal and spectroscopic data.

Observation of the influence of dipolar and spin frustration effects on the magnetocaloric properties of a trigonal prismatic {Gd7} molecular nanomagnet

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.

Copper Lanthanide Phosphonate Cages: Highly Symmetric {Cu3Ln9P6} and {Cu6Ln6P6} Clusters with C3v and D3h Symmetry

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.

Systematic Study of a Family of Butterfly-Like {M2Ln2} Molecular Magnets (M = MgII, MnIII, CoII, NiII, and CuII; Ln = YIII, GdIII, TbIII, DyIII, HoIII, and ErIII)

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).

Coherent electron spin manipulation in a dilute oriented ensemble of molecular nanomagnets: pulsed EPR on doped single crystals

Co-reporter:Fabrizio Moro, Danielle Kaminski, Floriana Tuna, George F. S. Whitehead, Grigore A. Timco, David Collison, Richard E. P. Winpenny, Arzhang Ardavan and Eric J. L. McInnes

Chemical Communications 2014 vol. 50(Issue 1) pp:91-93

Publication Date(Web):04 Nov 2013

DOI:10.1039/C3CC46326E

Doping a Cr7Zn molecular nanomagnet into a diamagnetic and isostructural host allows pulsed X-band EPR on single crystals, including relaxation and nutation experiments on the S = 3/2 ground state.

Iron Lanthanide Phosphonate Clusters: {Fe6Ln6P6} Wells—Dawson-like Structures with D3d Symmetry

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.

Large Zero-Field Splittings of the Ground Spin State Arising from Antisymmetric Exchange Effects in Heterometallic Triangles

Co-reporter:Samantha A. Magee;Dr. Stephen Sproules;Dr. Anne-Laure Barra;Dr. Grigore A. Timco;Nicholas F. Chilton; David Collison; Richard E. P. Winpenny; Eric J. L. McInnes

Angewandte Chemie 2014 Volume 126( Issue 21) pp:5414-5417

Publication Date(Web):

DOI:10.1002/ange.201400655

Abstract

[Ru₂Mn(O)(O₂CtBu)₆(py)₃] has an S=⁵/₂ ground state with a very large zero-field splitting (ZFS) of D=2.9 cm⁻¹, as characterized by EPR spectroscopy at 4–330 GHz. This is far too large to be due to the Mn^II ion (D <0.2 cm⁻¹), as shown from the {Fe₂Mn} analogue, but can be modeled by antisymmetric exchange effects.

Rcktitelbild: Large Zero-Field Splittings of the Ground Spin State Arising from Antisymmetric Exchange Effects in Heterometallic Triangles (Angew. Chem. 21/2014)

Co-reporter:Samantha A. Magee;Dr. Stephen Sproules;Dr. Anne-Laure Barra;Dr. Grigore A. Timco;Nicholas F. Chilton; David Collison; Richard E. P. Winpenny; Eric J. L. McInnes

Angewandte Chemie 2014 Volume 126( Issue 21) pp:

Publication Date(Web):

DOI:10.1002/ange.201401141

Back Cover: Large Zero-Field Splittings of the Ground Spin State Arising from Antisymmetric Exchange Effects in Heterometallic Triangles (Angew. Chem. Int. Ed. 21/2014)

Co-reporter:Samantha A. Magee;Dr. Stephen Sproules;Dr. Anne-Laure Barra;Dr. Grigore A. Timco;Nicholas F. Chilton; David Collison; Richard E. P. Winpenny; Eric J. L. McInnes

Angewandte Chemie International Edition 2014 Volume 53( Issue 21) pp:

Publication Date(Web):

DOI:10.1002/anie.201401141

Large Zero-Field Splittings of the Ground Spin State Arising from Antisymmetric Exchange Effects in Heterometallic Triangles

Co-reporter:Samantha A. Magee;Dr. Stephen Sproules;Dr. Anne-Laure Barra;Dr. Grigore A. Timco;Nicholas F. Chilton; David Collison; Richard E. P. Winpenny; Eric J. L. McInnes

Angewandte Chemie International Edition 2014 Volume 53( Issue 21) pp:5310-5313

Publication Date(Web):

DOI:10.1002/anie.201400655

Abstract

[Ru₂Mn(O)(O₂CtBu)₆(py)₃] has an S=⁵/₂ ground state with a very large zero-field splitting (ZFS) of D=2.9 cm⁻¹, as characterized by EPR spectroscopy at 4–330 GHz. This is far too large to be due to the Mn^II ion (D <0.2 cm⁻¹), as shown from the {Fe₂Mn} analogue, but can be modeled by antisymmetric exchange effects.

Molecular amino-phosphonate cobalt–lanthanide clusters

Co-reporter:Eufemio Moreno Pineda, Floriana Tuna, Robin G. Pritchard, Andrew C. Regan, Richard E. P. Winpenny and Eric J. L. McInnes

Chemical Communications 2013 vol. 49(Issue 34) pp:3522-3524

Publication Date(Web):25 Mar 2013

DOI:10.1039/C3CC40907D

The use of 1-amino-1-cyclohexyl phosphonic acid, a functionalised phosphonate, leads to the synthesis of two new structural types for 3d–4f phosphonate cages with unusual structural cores and which show high magnetocaloric effects.

Wells–Dawson Cages as Molecular Refrigerants

Co-reporter:Eufemio Moreno Pineda ; Floriana Tuna ; Yan-Zhen Zheng ; Richard E. P. Winpenny

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.

Single-Molecule Magnetism in a Single-Ion Triamidoamine Uranium(V) Terminal Mono-Oxo Complex

Co-reporter:David M. King;Dr. Floriana Tuna;Dr. Jonathan McMaster;Dr. William Lewis; Alexer J. Blake; Eric J. L. McInnes;Dr. Stephen T. Liddle

Angewandte Chemie International Edition 2013 Volume 52( Issue 18) pp:4921-4924

Publication Date(Web):

DOI:10.1002/anie.201301007

Single-Molecule Magnetism in a Single-Ion Triamidoamine Uranium(V) Terminal Mono-Oxo Complex

Co-reporter:David M. King;Dr. Floriana Tuna;Dr. Jonathan McMaster;Dr. William Lewis; Alexer J. Blake; Eric J. L. McInnes;Dr. Stephen T. Liddle

Angewandte Chemie 2013 Volume 125( Issue 18) pp:5021-5024

Publication Date(Web):

DOI:10.1002/ange.201301007

Suppression of the Jahn–Teller distortion in a six-coordinate copper(II) complex by doping it into a host lattice

Co-reporter:Rebecca Docherty, Floriana Tuna, Colin A. Kilner, Eric J. L. McInnes and Malcolm A. Halcrow

Chemical Communications 2012 vol. 48(Issue 34) pp:4055-4057

Publication Date(Web):06 Mar 2012

DOI:10.1039/C2CC30873H

The electronic structures of [Cu(terpy)2]2+ and [Cu(bpp)2]2+ (bpp = 2,6-di[pyrazol-1-yl]pyridine) are different, when doped into [M(bpp)2][BF4]2 (M2+ = Fe2+ or Zn2+). The [Cu(terpy)2]2+ dopant is a typical pseudo-Jahn–Teller elongated copper(II) center. However, the [Cu(bpp)2]2+ sites show EPR spectra consistent with a tetragonally compressed {dz2}1 configuration.

Chromium(III) stars and butterflies: synthesis, structural and magnetic studies of tetrametallic clusters

Co-reporter:Luke J. Batchelor, Mario Sander, Floriana Tuna, Madeleine Helliwell, Fabrizio Moro, Joris van Slageren, Enrique Burzurí, Oscar Montero, Marco Evangelisti, Fernando Luis and Eric J. L. McInnes

Dalton Transactions 2011 vol. 40(Issue 19) pp:5278-5284

Publication Date(Web):05 Apr 2011

DOI:10.1039/C1DT10172B

We report the synthesis, structures and magnetic properties of a series of chromium(III) metal-centered triangle (or “star”) clusters, [Cr4{RC(CH2O)3}2(4,4′-R′2-bipy)3Cl6] [R = Et, R′ = H (2); R = HOCH2, R′ = H (3); R = Et, R′ = tBu (4)], prepared by two-step solvothermal reactions starting from [CrCl3(thf)3]. The product of the first stage of this reaction is the salt [Cr(bipy)2Cl2]2[Cr2Cl8(MeCN)2] (1). In the absence of the diimine, a different family of tetrametallics is isolated: the butterfly complexes [Cr4{EtC(CH2O)3}2{NH(C(R)NH)2}2Cl6] (R = Me (5), Et (6), Ph (7)] where the chelating N-acetimidoylacetamidine NH(C(R)NH)2 ligands are formed in situ via condensation of the nitrile solvents (RCN) under solvothermal conditions. Magnetic measurements show the chromium stars to have an isolated S = 3 ground state, arising from antiferromagnetic coupling between the central and peripheral metal ions, analogous to the well-known Fe(III) stars. Bulk antiferromagnetic ordering is observed at 0.6 K. The butterfly complexes have a singlet ground state, with a low-lying S = 1 first excited state, due to dominant wing-body antiferromagnetic coupling.

A Spectroscopic Investigation of Magnetic Exchange Between Highly Anisotropic Spin Centers

Co-reporter:Dr. Angelika B. Boeer;Dr. Anne-Laure Barra; Liviu F. Chibotaru; David Collison; Eric J. L. McInnes;Dr. Richard A. Mole;Dr. Giovanna G. Simeoni;Dr. Grigore A. Timco;Dr. Liviu Ungur;Dr. Tobias Unruh; Richard E. P. Winpenny

Angewandte Chemie 2011 Volume 123( Issue 17) pp:4093-4097

Publication Date(Web):

DOI:10.1002/ange.201100306

A Spectroscopic Investigation of Magnetic Exchange Between Highly Anisotropic Spin Centers

Co-reporter:Dr. Angelika B. Boeer;Dr. Anne-Laure Barra; Liviu F. Chibotaru; David Collison; Eric J. L. McInnes;Dr. Richard A. Mole;Dr. Giovanna G. Simeoni;Dr. Grigore A. Timco;Dr. Liviu Ungur;Dr. Tobias Unruh; Richard E. P. Winpenny

Angewandte Chemie International Edition 2011 Volume 50( Issue 17) pp:4007-4011

Publication Date(Web):

DOI:10.1002/anie.201100306

Low-valent vanadium catecholate clusters

Co-reporter:Emma Scales, Lorenzo Sorace, Andrea Dei, Andrea Caneschi, Christopher A. Muryn, David Collison and Eric J. L. McInnes

Chemical Science 2010 vol. 1(Issue 2) pp:221-225

Publication Date(Web):26 May 2010

DOI:10.1039/C0SC00142B

A simple synthetic route to low-valent vanadium catecholate clusters, via solvothermal reaction of [V(acac)3] with catechols in alcohols, is presented. The syntheses and X-ray structures of [VIII6O(dbcat)4(OMe)8(MeOH)2] (1; which has the Lindqvist structure), [VIII6O2(dbcat)2(dbsq)2(acac)2(PhCO2)4(EtO)2] (2; which could alternatively be formulated as [VIII4VIV2O2(dbcat)4(acac)2(PhCO2)4(EtO)2]) and [VIV2(dbcat)4(EtOH)2] (3) are reported (dbcat2− = 3,5-tBu2-catecholate; dbsq− = 3,5-tBu2-semiquinone). The X-ray structures of the primary products of the reactions of 1 and 3 with atmospheric oxygen, [V6O3(“dbcat”)4(OMe)8] (4) and [V2O2(“dbcat”)4] (5), are also reported—the assignments of redox states for these four-electron oxidised species are more ambiguous.

Tripodal Thiols as Ligands for Molecular Magnets: Very Strong Antiferromagnetic Exchange Interactions in Vanadium(III) Clusters

Co-reporter:Luke J. Batchelor;Emma Fitzgerald;Dr. Joanna Wolowska;Dr. Joseph J. W. McDouall ; Eric J. L. McInnes

Chemistry - A European Journal 2010 Volume 16( Issue 36) pp:11082-11088

Publication Date(Web):

DOI:10.1002/chem.201000823

Abstract

The synthesis, structural and magnetic characterisation of [V^III₃O(tmme)₂(diimine)₂Cl] [diimine=2,2′-bipyridine (1) or 1,10-phenanthroline (2)] and (HNEt₃)₂[V^III₄O(tmme)₄] (3) is reported, in which H₃tmme is tris(mercaptomethyl)ethane, MeC(CH₂SH)₃, the thiol analogue of the famous tripodal alcohol ligands typified by H₃thme [tris(hydroxymethyl)ethane, MeC(CH₂OH)₃]. Complexes 1 and 3 have “T-shaped” and square topologies, respectively, and the latter is centred on a rare example of a square-planar oxide. The tri-thiolate ligands bind the periphery of the clusters and provide such strong antiferromagnetic exchange pathways that in both cases only a single total spin state is occupied up to room temperature, in the absence of metal–metal bonding. Magnetic data, electronic structure calculations and electrochemical data are reported.

An All-Vanadium(III) Hexametalate Lindqvist Structure and Its Chromium and Iron Analogues

Co-reporter:LukeJ. Batchelor;Rachel Shaw Dr.;SophieJ. Markey;Madeline Helliwell Dr. ;Eric J.L. McInnes

Chemistry - A European Journal 2010 Volume 16( Issue 19) pp:5554-5557

Publication Date(Web):

DOI:10.1002/chem.201000222

Tri-, tetra- and octa-metallic vanadium(III) clusters from new, simple starting materials: interplay of exchange and anisotropy effects

Co-reporter:Ian S. Tidmarsh, Luke J. Batchelor, Emma Scales, Rebecca H. Laye, Lorenzo Sorace, Andrea Caneschi, Jürgen Schnack and Eric J. L. McInnes

Dalton Transactions 2009 (Issue 43) pp:9402-9409

Publication Date(Web):04 Sep 2009

DOI:10.1039/B911586B

The crystal structure of the monomeric vanadium(III) species mer-[V(bipy)Cl3(MeCN)] (1; bipy = 2,2′-bipyridine) is reported. The solvothermal reaction of [V(bipy)Cl3(MeCN)]with Na(O2CPh) yields the T-shaped cluster [V3(O)Cl3(O2CPh)2(bipy)2(OEt)2], magnetic studies of which show strong intramolecular antiferromagnetic coupling giving a well isolated S = 1 ground state. Solvothermal treatment of 1 with triols yields a series of polymetallic clusters [V4Cl6(thme)2(bipy)3], [V3Cl4(Hcht)2(bipy)2]Cl and [V8(OH)2Cl4(cht)4(O2CPh)6(bipy)2], structurally related to previously reported {M4} centred triangles. Magnetic studies of this series reveal very weak intramolecular antiferromagnetic exchange and very strong local zero-field splitting effects.

Ferromagnetic NiII Discs

Co-reporter:Richard T.W. Scott;LeighF. Jones Dr.;IanS. Tidmarsh Dr.;Barbara Breeze Dr.;RebeccaH. Laye Dr.;Joanna Wolowska Dr.;DanielJ. Stone Dr.;Anna Collins Dr.;Simon Parsons ;Wolfgang Wernsdorfer Dr.;Guillem Aromí Dr.;EricJ.L. McInnes ;EuanK. Brechin Dr.

Chemistry - A European Journal 2009 Volume 15( Issue 45) pp:12389-12398

Publication Date(Web):

DOI:10.1002/chem.200901865

Abstract

A family of planar disc-like hexa-, octa- and decametallic Ni^II complexes exhibit dominant ferromagnetic exchange. The deca- and octametallic clusters [Ni^II₁₀(tmp)₂(N₃)₈(acac)₆(MeOH)₆] (1, H₃tmp=1,1,1-tris(hydroxymethyl)propane; acac=acetylacetonate) and [Ni^II₈(thme)₂(O₂CPh)₄(Cl)₆(MeCN)₆(H₂O)₂] (2, H₃thme=1,1,1-tris(hydroxymethyl)ethane) represent rare examples of Ni^II-based single-molecule magnets, and [Ni^II₁₀] (1) possesses the largest barrier to magnetisation reversal of any Ni^II single-molecule magnet to date.

Solution identification and solid state characterisation of a heterometallic polyoxometalate {Mo11V7}: [MoVI11VV5VIV2O52(μ9-SO3)]7−

Co-reporter:Haralampos N. Miras, Daniel J. Stone, Eric J. L. McInnes, Raphael G. Raptis, Peter Baran, George I. Chilas, Michael P. Sigalas, Themistoklis A. Kabanos and Leroy Cronin

Chemical Communications 2008 (Issue 39) pp:4703-4705

Publication Date(Web):15 Sep 2008

DOI:10.1039/B811279G

A polyoxomolybdenum/vanadium-sulfite {M18} cluster-based compound, [MoVI11VV5VIV2O52(μ9-SO3)]7−, is reported that exhibits a unique structural motif, arising from the incorporation of five VV and two VIV ions into a {M18} cluster framework templated by SO32−; this cluster compostion was first identified using cryospray mass spectrometry.

Synthesis, structural, magnetic and high frequency EPR studies on a hexametallic Fe(III) complex with a highly rhombic S = 5 ground state

Co-reporter:Paul Cooper, Floriana Tuna, Muralidharan Shanmugam, Lorenzo Sorace, Sarah L. Heath, David Collison, Eric J.L. McInnes, Richard E.P. Winpenny

Inorganica Chimica Acta 2008 Volume 361(12–13) pp:3663-3668

Publication Date(Web):1 September 2008

DOI:10.1016/j.ica.2008.03.081

The synthesis, crystal structure and magnetic properties of the hexametallic Fe(III) cluster [Fe6IIIO2(OH)2{(C4N2H2SMe)2C(OH)O}2(tBuCO2)10] (1) are reported. Compound 1 was prepared by reaction of mixed-valent [Fe3O(tBuCO2)6(py)3] with one equivalent of the new ligand di-2-(4-methylthio)pyrimidyl ketone (DTPK) in MeCN solution. Compound 1 consists of a planar array of six Fe(III) ions comprising two [Fe3(μ3-O)]7+ subunits that are related by an inversion centre and linked at two of their apices, each via one μ-hydroxide and two μ-carboxylate groups. Variable temperature magnetic susceptibility and low temperature magnetization measurements show a well isolated S = 5 electronic spin ground state. Variable temperature W-band EPR measurements on a polycrystalline sample give well resolved spectra and simulations confirm a negative zero-field splitting of D = −0.224 cm−1 but also reveal a very rhombic nature (E/|D| = 0.27). Although 1 has a well isolated S = 5 ground state with a negative magnetic anisotropy, it is not a SMM due to this large rhombicity.[Fe6O2(OH)2{C4N2H2SMe}2C(OH)O}2(tBuCO2)10] consists of two co-planar [Fe3(μ3-O)]7+ triangles, a structural type which gives rise to a well isolated S = 5 spin ground state. HF-EPR reveals a substantial negative zero-field splitting but also a high rhombicity (E/|D| = 0.27), explaining the absence of SMM behaviour in this class of complex.

Supertetrahedral and Bi-supertetrahedral Cages: Synthesis, Structures, and Magnetic Properties of Deca- and Enneadecametallic Cobalt(II) Clusters

Co-reporter:Laurent Lisnard Dr.;Floriana Tuna Dr.;Andrea Cini Dr.;Marco Affronte ;RichardE.P. Winpenny ;EricJ.L. McInnes

Angewandte Chemie 2008 Volume 120( Issue 50) pp:9841-9845

Publication Date(Web):

DOI:10.1002/ange.200804147

Supertetrahedral and Bi-supertetrahedral Cages: Synthesis, Structures, and Magnetic Properties of Deca- and Enneadecametallic Cobalt(II) Clusters

Co-reporter:Laurent Lisnard Dr.;Floriana Tuna Dr.;Andrea Cini Dr.;Marco Affronte ;RichardE.P. Winpenny ;EricJ.L. McInnes

Angewandte Chemie International Edition 2008 Volume 47( Issue 50) pp:9695-9699

Publication Date(Web):

DOI:10.1002/anie.200804147

Large spin, magnetically anisotropic, octametallic vanadium(III) clusters with strong ferromagnetic coupling

Co-reporter:Rachel Shaw, Floriana Tuna, Wolfgang Wernsdorfer, Anne-Laure Barra, David Collison and Eric J. L. McInnes

Chemical Communications 2007 (Issue 48) pp:5161-5163

Publication Date(Web):05 Oct 2007

DOI:10.1039/B710732C

Syntheses, structural and magnetic and EPR data are reported for two octametallic VIII clusters with anisotropic S = 4 ground states arising from strong ferromagnetic exchange interactions.

Studies of a linear single-molecule magnet

Co-reporter:Alessandro Prescimone, Joanna Wolowska, Gopalan Rajaraman, Simon Parsons, Wolfgang Wernsdorfer, Murlaee Murugesu, George Christou, Stergios Piligkos, Eric J. L. McInnes and Euan K. Brechin

Dalton Transactions 2007 (Issue 45) pp:5282-5289

Publication Date(Web):15 Oct 2007

DOI:10.1039/B713163A

Reaction of the dinuclear complex [Mn2O2(bpy)4](ClO4)3 with H3cht (cis,cis-1,3,5-cyclohexanetriol) in MeCN produces the complex [Mn3(Hcht)2(bpy)4](ClO4)3·Et2O·2MeCN (1·Et2O·2MeCN). Dc magnetic susceptibility measurements reveal the existence of weak ferromagnetic exchange between the three Mn ions, leading to a spin ground state of S = 7, with D = −0.23 cm−1. W-Band (94 GHz) EPR measurements on restrained powdered crystalline samples confirm the S = 7 ground state and determine the ground state zero-field splitting (ZFS) parameters of D = −0.14 cm−1 and B40= +1.5 × 10−5 cm−1. The apparent 4th order behaviour is due to a breakdown of the strong exchange limit approximation (J ≈ d, the single-ion ZFS). Single crystal dc relaxation decay and hysteresis loop measurements reveal the molecule to have an appreciable energy barrier to magnetization relaxation, displaying low temperature sweep rate and temperature-dependent hysteresis loops. Density functional studies confirm the ferromagnetic exchange coupling between the Mn ions.

Highly Reduced, Polyoxo(alkoxo)vanadium(III/IV) Clusters

Co-reporter:Ian S. Tidmarsh Dr.;Rebecca H. Laye Dr.;Paul R. Brearley;Maheswaran Shanmugam Dr.;E. Carolina Sañudo Dr.;Lorenzo Sorace Dr.;Andrea Caneschi ;Eric J. L. McInnes

Chemistry - A European Journal 2007 Volume 13(Issue 22) pp:

Publication Date(Web):22 MAY 2007

DOI:10.1002/chem.200700247

A family of high nuclearity oxo(alkoxo)vanadium clusters in unprecedentedly low oxidation states is reported, synthesised from simple vanadium diketonate precursors in alcohols under solvothermal conditions. Crystal structures of [V₁₈(O)₁₂(OH)₂(H₂O)₄(EtO)₂₂(O₂CPh)₆(acac)₂] (1), [V₁₆Na₂(O)₁₈(EtO)₁₆(EtOH)₂(O₂CPh)₆(HO₂CPh)₂]_∞ (2), [V₁₃(O)₁₃(EtO)₁₅(EtOH)(RCO₂)₃] in which R=adamantyl (3) or Ph₃C (4), and [V₁₁(O)₁₂(EtO)₁₃(EtOH)(Ph₃CCO₂)₂(MePO₃)] (5) are reported, revealing these to be {V^III₁₆V^IV₂} (1), {V^III₉V^IV₃V^V} (3 and 4) and {V^III₃V^IV₈} (5) clusters, while 2 consists of isolated {V^III₈V^IV₈} clusters bridged into polymeric chains by {Na₂(OEt)₂} fragments. Solvothermal conditions are essential to the formation of these species, and the level of oxidation of the isolated clusters is in part controlled by the crystallisation time, with the lowest mean-oxidation-state species being isolated by direct crystallisation on controlled cooling of the reaction solutions.

Synthesis of Molecular Vanadium(III) Phosphonates

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 V^III 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 {V^III₁₂(V^IVO)} cluster shown in the picture (V green, P purple, O red, C black). Preliminary magnetic studies are also reported.

Synthesis of Molecular Vanadium(III) Phosphonates

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 V^III-Analoga sind dagegen äußerst dünn gesäht. Aus VCl₃ und Phosphonaten entsteht unter Solvothermalbedingungen eine ganze Familie entsprechender Vanadium(III)-phosphonate, darunter der schichtförmige Cluster {V^III₁₂(V^IVO)} im Bild (V grün, P violett, O rot, C schwarz). Erste Untersuchungen zum magnetischen Verhalten werden ebenfalls beschrieben.

A high-nuclearity, beyond “fully reduced” polyoxo(alkoxo)vanadium(III/IV) cage

Co-reporter:Ian S. Tidmarsh, Rebecca H. Laye, Paul R. Brearley, Maheswaran Shanmugam, E. Carolina Sañudo, Lorenzo Sorace, Andrea Caneschi and Eric J. L. McInnes

Chemical Communications 2006 (Issue 24) pp:2560-2562

Publication Date(Web):18 May 2006

DOI:10.1039/B605106E

The solvothermal synthesis, crystal structure and preliminary magnetic studies are reported of the first high nuclearity VIII-based polyoxo(alkoxo)vanadium cage, a VIII16VIV2 complex.

Tetrahedra, Super-Tetrahedra, Bipyramids, Boxes and More: Polymetallic Clusters of Benzotriazole

Co-reporter:David Collison;Euan K. Brechin

European Journal of Inorganic Chemistry 2006 Volume 2006(Issue 14) pp:

Publication Date(Web):1 JUN 2006

DOI:10.1002/ejic.200600206

The syntheses, structures and magnetic properties of a host of polymetallic 3d transition-metal clusters made with the pro-ligand benzotriazole (BtaH) and its analogues are reported. These range from a family of tetradecametallic clusters with spin ground states as large as S ≈ 25, to decametallic vanadium “boxes”, to iron and manganese tetra- and super-tetrahedra, to hexaicosametallic manganese single-molecule magnets. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

A Family of Ferro- and Antiferromagnetically Coupled Decametallic Chromium(III) Wheels

Co-reporter:David M. Low Dr.;Gopalan Rajaraman Dr.;Madeleine Helliwell Dr.;Grigore Timco Dr.;Joris van Slageren Dr.;Roberta Sessoli ;Stefan T. Ochsenbein;Rol Bircher;Christopher Dobe;Oliver Waldmann Dr.;Hans-Ulrich Güdel ;Mark A. Adams Dr.;Eliseo Ruiz ;Santiago Alvarez Dr.

Chemistry - A European Journal 2006 Volume 12(Issue 5) pp:

Publication Date(Web):28 NOV 2005

DOI:10.1002/chem.200501041

The synthesis and crystal structures of a family of decametallic Cr^III “molecular wheels” are reported, namely [Cr₁₀(OR)₂₀(O₂CR′)₁₀] [R′=Me, R=Me (1), Et (2); R′=Et, R=Me (3), Et (4); R′=CMe₃, R=Me (5), Et (6)]. Magnetic studies on 1–6 reveal a remarkable dependence of the magnetic behaviour on the nature of R. In each pair of complexes with a common carboxylate (R′) the nearest neighbour Cr⋅⋅⋅Cr magnetic exchange coupling is more antiferromagnetic for the ethoxide-bridged (R=Et) cluster than for the methoxide analogue. In complexes 2, 4 and 6 the overall coupling is weakly antiferromagnetic resulting in diamagnetic (S=0) ground states for the cluster, whilst in 1 and 5 it is weakly ferromagnetic thus resulting in very high-spin ground states. This ground state has been probed directly in the perdeuterated version of 1 ([D]1) by inelastic neutron scattering experiments, and these support the S=15 ground state expected for ferromagnetic coupling of ten Cr^III ions, and they also indicate that a single J-value model is inadequate. The ground state of 5 is large but not well defined. The trends in J on changing R are further supported by density functional calculations on 1–6, which are in excellent agreement with experiment. The very large changes in the nature of the ground state between 1 and 2, and 5 and 6 are the result of relatively small changes in J that happen to cross J=0, hence changing the sign of J.

Synthesis, structure and magnetic properties of a decametallic Ni single-molecule magnet

Co-reporter:Guillem Aromí, Simon Parsons, Wolfgang Wernsdorfer, Euan K. Brechin and Eric J. L. McInnes

Chemical Communications 2005 (Issue 40) pp:5038-5040

Publication Date(Web):13 Sep 2005

DOI:10.1039/B510097F

Ferromagnetic exchange between the ten Ni2+ ions in the complex [Ni10(tmp)2(N3)8(acac)6(MeOH)6] leads to a spin ground state of S = 10; single crystal Mvs. H studies reveal the temperature and sweep rate dependent hysteresis loops expected for a single-molecule magnet.

A family of heterometallic wheels containing potentially fourteen hundred siblings

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.

Coherent electron spin manipulation in a dilute oriented ensemble of molecular nanomagnets: pulsed EPR on doped single crystals

Co-reporter:Fabrizio Moro, Danielle Kaminski, Floriana Tuna, George F. S. Whitehead, Grigore A. Timco, David Collison, Richard E. P. Winpenny, Arzhang Ardavan and Eric J. L. McInnes

Chemical Communications 2014 - vol. 50(Issue 1) pp:NaN93-93

Publication Date(Web):2013/11/04

DOI:10.1039/C3CC46326E

Doping a Cr7Zn molecular nanomagnet into a diamagnetic and isostructural host allows pulsed X-band EPR on single crystals, including relaxation and nutation experiments on the S = 3/2 ground state.

Tri-, tetra- and octa-metallic vanadium(III) clusters from new, simple starting materials: interplay of exchange and anisotropy effects

Co-reporter:Ian S. Tidmarsh, Luke J. Batchelor, Emma Scales, Rebecca H. Laye, Lorenzo Sorace, Andrea Caneschi, Jürgen Schnack and Eric J. L. McInnes

Dalton Transactions 2009(Issue 43) pp:NaN9409-9409

Publication Date(Web):2009/09/04

DOI:10.1039/B911586B

The crystal structure of the monomeric vanadium(III) species mer-[V(bipy)Cl3(MeCN)] (1; bipy = 2,2′-bipyridine) is reported. The solvothermal reaction of [V(bipy)Cl3(MeCN)]with Na(O2CPh) yields the T-shaped cluster [V3(O)Cl3(O2CPh)2(bipy)2(OEt)2], magnetic studies of which show strong intramolecular antiferromagnetic coupling giving a well isolated S = 1 ground state. Solvothermal treatment of 1 with triols yields a series of polymetallic clusters [V4Cl6(thme)2(bipy)3], [V3Cl4(Hcht)2(bipy)2]Cl and [V8(OH)2Cl4(cht)4(O2CPh)6(bipy)2], structurally related to previously reported {M4} centred triangles. Magnetic studies of this series reveal very weak intramolecular antiferromagnetic exchange and very strong local zero-field splitting effects.

Molecular amino-phosphonate cobalt–lanthanide clusters

Co-reporter:Eufemio Moreno Pineda, Floriana Tuna, Robin G. Pritchard, Andrew C. Regan, Richard E. P. Winpenny and Eric J. L. McInnes

Chemical Communications 2013 - vol. 49(Issue 34) pp:NaN3524-3524

Publication Date(Web):2013/03/25

DOI:10.1039/C3CC40907D

The use of 1-amino-1-cyclohexyl phosphonic acid, a functionalised phosphonate, leads to the synthesis of two new structural types for 3d–4f phosphonate cages with unusual structural cores and which show high magnetocaloric effects.

Chromium(III) stars and butterflies: synthesis, structural and magnetic studies of tetrametallic clusters

Co-reporter:Luke J. Batchelor, Mario Sander, Floriana Tuna, Madeleine Helliwell, Fabrizio Moro, Joris van Slageren, Enrique Burzurí, Oscar Montero, Marco Evangelisti, Fernando Luis and Eric J. L. McInnes

Dalton Transactions 2011 - vol. 40(Issue 19) pp:NaN5284-5284

Publication Date(Web):2011/04/05

DOI:10.1039/C1DT10172B

We report the synthesis, structures and magnetic properties of a series of chromium(III) metal-centered triangle (or “star”) clusters, [Cr4{RC(CH2O)3}2(4,4′-R′2-bipy)3Cl6] [R = Et, R′ = H (2); R = HOCH2, R′ = H (3); R = Et, R′ = tBu (4)], prepared by two-step solvothermal reactions starting from [CrCl3(thf)3]. The product of the first stage of this reaction is the salt [Cr(bipy)2Cl2]2[Cr2Cl8(MeCN)2] (1). In the absence of the diimine, a different family of tetrametallics is isolated: the butterfly complexes [Cr4{EtC(CH2O)3}2{NH(C(R)NH)2}2Cl6] (R = Me (5), Et (6), Ph (7)] where the chelating N-acetimidoylacetamidine NH(C(R)NH)2 ligands are formed in situ via condensation of the nitrile solvents (RCN) under solvothermal conditions. Magnetic measurements show the chromium stars to have an isolated S = 3 ground state, arising from antiferromagnetic coupling between the central and peripheral metal ions, analogous to the well-known Fe(III) stars. Bulk antiferromagnetic ordering is observed at 0.6 K. The butterfly complexes have a singlet ground state, with a low-lying S = 1 first excited state, due to dominant wing-body antiferromagnetic coupling.

Suppression of the Jahn–Teller distortion in a six-coordinate copper(II) complex by doping it into a host lattice

Co-reporter:Rebecca Docherty, Floriana Tuna, Colin A. Kilner, Eric J. L. McInnes and Malcolm A. Halcrow

Chemical Communications 2012 - vol. 48(Issue 34) pp:NaN4057-4057

Publication Date(Web):2012/03/06

DOI:10.1039/C2CC30873H

The electronic structures of [Cu(terpy)2]2+ and [Cu(bpp)2]2+ (bpp = 2,6-di[pyrazol-1-yl]pyridine) are different, when doped into [M(bpp)2][BF4]2 (M2+ = Fe2+ or Zn2+). The [Cu(terpy)2]2+ dopant is a typical pseudo-Jahn–Teller elongated copper(II) center. However, the [Cu(bpp)2]2+ sites show EPR spectra consistent with a tetragonally compressed {dz2}1 configuration.

Low-valent vanadium catecholate clusters

Co-reporter:Emma Scales, Lorenzo Sorace, Andrea Dei, Andrea Caneschi, Christopher A. Muryn, David Collison and Eric J. L. McInnes

Chemical Science (2010-Present) 2010 - vol. 1(Issue 2) pp:NaN225-225

Publication Date(Web):2010/05/26

DOI:10.1039/C0SC00142B

A simple synthetic route to low-valent vanadium catecholate clusters, via solvothermal reaction of [V(acac)3] with catechols in alcohols, is presented. The syntheses and X-ray structures of [VIII6O(dbcat)4(OMe)8(MeOH)2] (1; which has the Lindqvist structure), [VIII6O2(dbcat)2(dbsq)2(acac)2(PhCO2)4(EtO)2] (2; which could alternatively be formulated as [VIII4VIV2O2(dbcat)4(acac)2(PhCO2)4(EtO)2]) and [VIV2(dbcat)4(EtOH)2] (3) are reported (dbcat2− = 3,5-tBu2-catecholate; dbsq− = 3,5-tBu2-semiquinone). The X-ray structures of the primary products of the reactions of 1 and 3 with atmospheric oxygen, [V6O3(“dbcat”)4(OMe)8] (4) and [V2O2(“dbcat”)4] (5), are also reported—the assignments of redox states for these four-electron oxidised species are more ambiguous.

Observation of the influence of dipolar and spin frustration effects on the magnetocaloric properties of a trigonal prismatic {Gd7} molecular nanomagnet

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.

Solution identification and solid state characterisation of a heterometallic polyoxometalate {Mo11V7}: [MoVI11VV5VIV2O52(μ9-SO3)]7−

Co-reporter:Haralampos N. Miras, Daniel J. Stone, Eric J. L. McInnes, Raphael G. Raptis, Peter Baran, George I. Chilas, Michael P. Sigalas, Themistoklis A. Kabanos and Leroy Cronin

Chemical Communications 2008(Issue 39) pp:NaN4705-4705

Publication Date(Web):2008/09/15

DOI:10.1039/B811279G

A polyoxomolybdenum/vanadium-sulfite {M18} cluster-based compound, [MoVI11VV5VIV2O52(μ9-SO3)]7−, is reported that exhibits a unique structural motif, arising from the incorporation of five VV and two VIV ions into a {M18} cluster framework templated by SO32−; this cluster compostion was first identified using cryospray mass spectrometry.

Studies of a linear single-molecule magnet

Co-reporter:Alessandro Prescimone, Joanna Wolowska, Gopalan Rajaraman, Simon Parsons, Wolfgang Wernsdorfer, Murlaee Murugesu, George Christou, Stergios Piligkos, Eric J. L. McInnes and Euan K. Brechin

Dalton Transactions 2007(Issue 45) pp:NaN5289-5289

Publication Date(Web):2007/10/15

DOI:10.1039/B713163A

Reaction of the dinuclear complex [Mn2O2(bpy)4](ClO4)3 with H3cht (cis,cis-1,3,5-cyclohexanetriol) in MeCN produces the complex [Mn3(Hcht)2(bpy)4](ClO4)3·Et2O·2MeCN (1·Et2O·2MeCN). Dc magnetic susceptibility measurements reveal the existence of weak ferromagnetic exchange between the three Mn ions, leading to a spin ground state of S = 7, with D = −0.23 cm−1. W-Band (94 GHz) EPR measurements on restrained powdered crystalline samples confirm the S = 7 ground state and determine the ground state zero-field splitting (ZFS) parameters of D = −0.14 cm−1 and B40= +1.5 × 10−5 cm−1. The apparent 4th order behaviour is due to a breakdown of the strong exchange limit approximation (J ≈ d, the single-ion ZFS). Single crystal dc relaxation decay and hysteresis loop measurements reveal the molecule to have an appreciable energy barrier to magnetization relaxation, displaying low temperature sweep rate and temperature-dependent hysteresis loops. Density functional studies confirm the ferromagnetic exchange coupling between the Mn ions.

[MIII2MII3]n+ trigonal bipyramidal cages based on diamagnetic and paramagnetic metalloligands

Co-reporter:S. Sanz, H. M. O'Connor, V. Martí-Centelles, P. Comar, M. B. Pitak, S. J. Coles, G. Lorusso, E. Palacios, M. Evangelisti, A. Baldansuren, N. F. Chilton, H. Weihe, E. J. L. McInnes, P. J. Lusby, S. Piligkos and E. K. Brechin

Chemical Science (2010-Present) 2017 - vol. 8(Issue 8) pp:NaN5535-5535

Publication Date(Web):2017/05/19

DOI:10.1039/C7SC00487G

A family of five [MIII2MII3]n+ trigonal bipyramidal cages (MIII = Fe, Cr and Al; MII = Co, Zn and Pd; n = 0 for 1–3 and n = 6 for 4–5) of formulae [Fe2Co3L6Cl6] (1), [Fe2Zn3L6Br6] (2), [Cr2Zn3L6Br6] (3), [Cr2Pd3L6(dppp)3](OTf)6 (4) and [Al2Pd3L6(dppp)3](OTf)6 (5) (where HL is 1-(4-pyridyl)butane-1,3-dione and dppp is 1,3-bis(diphenylphosphino)propane) are reported. Neutral cages 1–3 were synthesised using the tritopic [MIIIL3] metalloligand in combination with the salts CoIICl2 and ZnIIBr2, which both act as tetrahedral linkers. The assembly of the cis-protected [PdII(dppp)(OTf)2] with [MIIIL3] afforded the anionic cages 4–5 of general formula [MIII2PdII3](OTf)6. The metallic skeleton of all cages describes a trigonal bipyramid with the MIII ions occupying the two axial sites and the MII ions sitting in the three equatorial positions. Direct current (DC) magnetic susceptibility, magnetisation and heat capacity measurements on 1 reveal weak antiferromagnetic exchange between the FeIII and CoII ions. EPR spectroscopy demonstrates that the distortion imposed on the {MO6} coordination sphere of [MIIIL3] by complexation in the {MIII2MII3} supramolecules results in a small, but measurable, increase of the zero field splitting at MIII. Complete active space self-consistent field (CASSCF) calculations on the three unique CoII sites of 1 suggest DCo ≈ −14 cm−1 and E/D ≈ 0.1, consistent with the magnetothermal and spectroscopic data.

Large spin, magnetically anisotropic, octametallic vanadium(III) clusters with strong ferromagnetic coupling

Co-reporter:Rachel Shaw, Floriana Tuna, Wolfgang Wernsdorfer, Anne-Laure Barra, David Collison and Eric J. L. McInnes

Chemical Communications 2007(Issue 48) pp:NaN5163-5163

Publication Date(Web):2007/10/05

DOI:10.1039/B710732C

Syntheses, structural and magnetic and EPR data are reported for two octametallic VIII clusters with anisotropic S = 4 ground states arising from strong ferromagnetic exchange interactions.

Eric J. L. McInnes

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