Mark Murrie

Cobalt(II) single-molecule magnets

This short tutorial review covers recent progress in the field of polynuclear cobalt(ii)-based complexes, which display slow magnetic relaxation at low temperature. Cobalt(ii) single-molecule magnets (SMMs) can display much larger magnetic anisotropies and hence, potentially higher blocking temperatures than SMMs based on ions where the zero-field splitting originates from a second order spin-orbit coupling, such as manganese(iii).

Polyoxometalate‐Mediated Self‐Assembly of Single‐Molecule Magnets: {[XW9O34]2[MnIII4MnII2O4(H2O)4]}12−

Last night of the POMs: The title compound (X=GeIV) exhibits slow relaxation of magnetization and quantum tunneling with a single-molecule magnetic behavior. Significant structural differences in the [MnIII4MnII2O4(H2O)4]8+ cluster core of the X=SiIV analogue modify the magnetic properties, thereby illustrating how polyoxometalate (POM) ligands can help in the systematic construction of nanoscale magnets.

Studies of a nickel-based single molecule magnet: resonant quantum tunnelling in an S = 12 moleculeElectronic supplementary information (ESI) available: saturation magnetisation at 150 mK; 1/χ′ vs. T. See http://www.rsc.org/suppdata/cc/b1/b108894g/

A cyclic complex [Ni(12)(chp)(12)(O(2)CMe)(12)(thf)(6)(H(2)O)(6)] (1) has been synthesised and studied (chp=6-chloro-2-pyridonate). Complex 1 exhibits ferromagnetic exchange between the S=1 centres, giving an S=12 spin ground state. Detailed studies demonstrate that it is a single-molecule magnet with an energy barrier of approximately 10 K for reorientation of magnetisation. Resonant quantum tunnelling is also observed. The field between resonances allows accurate measurement of D, which is 0.067 K. Inelastic neutron scattering studies have allowed exchange parameters to be derived accurately, which was impossible from susceptibility data alone. Three exchange interactions are required: two ferromagnetic nearest neighbour interactions of approximately 11 and 2 cm(-1) and an anti-ferromagnetic next nearest neighbour interaction of -0.9 cm(-1).

Studies of a Nickel-Based Single-Molecule Magnet

A cyclic complex [Ni12(chp)12(O2CMe)12(thf)6(H2O)6] (1) has been synthesised and studied (chp=6-chloro-2-pyridonate). Complex 1 exhibits ferromagnetic exchange between the S=1 centres, giving an S=12 spin ground state. Detailed studies demonstrate that it is a single-molecule magnet with an energy barrier of approximately 10 K for reorientation of magnetisation. Resonant quantum tunnelling is also observed. The field between resonances allows accurate measurement of D, which is 0.067 K. Inelastic neutron scattering studies have allowed exchange parameters to be derived accurately, which was impossible from susceptibility data alone. Three exchange interactions are required: two ferromagnetic nearest neighbour interactions of approximately 11 and 2 cm−1 and an anti-ferromagnetic next nearest neighbour interaction of −0.9 cm−1.

A mixed-valence Co-7 single-molecule magnet with C-3 symmetry

The synthesis, structure and magnetic properties of [Co(II)(4)Co(III)(3)(HL)(6)(NO(3))(3)(H(2)O)(3)](2+) [H(3)L = H(2)NC(CH(2)OH)(3)] are reported: the complex is an exchange-biased single molecule magnet.

Synthesis and characterisation of a Ni(4) single-molecule magnet with S(4) symmetry

[Ni4Cl4(HL)4] () {H2L=HN(CH2CH2OH)2} has S4 symmetry and crystallises in the tetragonal space group I4(1)/a. Two exchange couplings are observed between the four Ni(II) centres, with J1=7.29 cm(-1) and J2=-2.08 cm(-1), leading to an S=4 ground state. The Ni4 complex shows the onset of frequency dependent signals in the out-of-phase ac susceptibility below 3 K. In single-crystal measurements carried out using a micro-SQUID, hysteresis loops are observed below 0.5 K, confirming that shows slow relaxation of magnetisation. The loops are temperature dependent but only weakly sweep rate dependent due to the presence of small intermolecular interactions, which hinder quantum tunnelling. This exchange bias between Ni4 molecules is also seen in high-frequency high-field EPR measurements, which give the parameters D=-0.75 cm(-1), B4 degrees=-6.7x10(-5) cm(-1) and gz=2.275.

[Mn6] under Pressure: A Combined Crystallographic and Magnetic Study†

Folding under pressure: Crystallographic studies on a Mn6 single-molecule magnet under high pressure conditions show the drastic structural changes of the magnetic core (see picture, Mn purple, O red, N blue), which impact on the magnetic properties of ferromagnetic exchange between the metal atoms will be in booster weaker, and under extremely high pressure, a transition to antiferromagnetic behavior.

Directed assembly of nanoscale Co(II)-substituted {Co9[P2W15]3} and {Co14[P2W15]4} polyoxometalates

Herein we report two structurally intriguing Co(ii)-substituted polyoxometalates, a {Co(9)[P(2)W(15)](3)} and {Co(14)[P(2)W(15)](4)} (compounds 1 and 2) that are formed from the same building blocks under subtly different conditions. Compound 1 displays a structure previously predicted but never before realised, whilst compound 2 is the first Co-containing Dawson-based single-molecule magnet and has a unique cruciform structure.

Field-Induced Slow Relaxation in a Monometallic Manganese(III) Single-Molecule Magnet

High-field electron paramagnetic resonance spectroscopy shows that the structurally distorted Mn(III) ion in Na5[Mn(L-tart)2]·12H2O (1; L-tart = L-tartrate) has a significant negative axial zero-field splitting and a small rhombic anisotropy (∼1% of D). Alternating-current magnetic susceptibility measurements demonstrate that 1, which contains isolated Mn(III) centers, displays slow relaxation of its magnetization under an applied direct-current magnetic field.

Pressure-induced Jahn–Teller switching in a Mn12 nanomagnet

Pressure-induced switching of a fast-relaxing single-molecule magnet to a slow-relaxing isomer is observed for the first time by using a combination of high pressure single-crystal X-ray diffraction and high pressure magnetic measurements.