Ferromagnetically Coupled Hydroxo-bridged Heptanuclear Ni(II) Wheel Cluster with S=7 Ground Spin State

A wheel-like heptanuclear Ni(II) cluster, [Ni7L61(mu(3)-OH)(6)]Cl-2 center dot 6MeOH (1) (HL1 = N-(3-amino-2,2-dimethylpropyl)-2-hydroxybenzamide), was synthesized, and its crystal structure and magnetic properties were investigated in detail. Magnetic characterization revealed the presence of intra-cluster ferro-magnetic coupling and the best fit for the data gave the following parameters: J(1) = +7.24 cm(-1), J(2) = +0.31 cm(-1), g = 2.16. The magnetization versus field measurements revealed that the saturated value is in accordance with an S = 7 ground state (M-5T = 14.5 mu(beta)). This appears to be the first reported example of an oxo-bridged Ni-7 wheel system with all metal centers ferromagnetically coupled and with an S = 7.