Hanspeter Andres, Reto Basler, Alexander J. Blake, Cyril Cadiou, Gregory Chaboussant, Craig M. Grant, Hans-Ulrich Güdel, Mark Murrie, Simon Parsons, Carley Paulsen, Fabrizzio Semadini, Vincent Villar, Wolfgang Wernsdorfer and Richard E. P. Winpenny
Studies of a Nickel-Based Single-Molecule Magnet
Chem. Eur. J. 8, 4867-4876 (2002)                       

Abstract: 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.