Orbital-Dependent Magnetic Properties of Molecular Cluster Containing High-Spin Co(II) Ions

To shed light on magnetic properties of the magnetic exchange molecular cluster containing the constituent metal ion with unquenched orbital angular momentum, as representative examples two octahedrally coordinated high-spin Co(II)-cluster complexes were synthesized and characterized: complex (1) [Co-3(Hbzp)(6)] [ClO4]2 center dot 2CH(3)OH center dot H2O (bzp = 2-benzoylpyridine) with a linear core Co(III)-Co(II)-Co(III) and complex (2) [Co4L(N-3)(4)(CH3CN)(4)](ClO4)(4)center dot 2H(2)O (L = Macrocyclic schiff base of tetra-2,6-pyridinedicarboxaldehyde-tetra-ethane-1,2-diamine) comprised by two nearly independent Co(II)-dimers. Following Lines' isotropic exchange approximation the magnetic interaction effective Hamiltonian was introduced, which includes the exchange interactions, the spin-orbit coupling, the low-symmetry crystal field, and the intercluster exchange interaction. On the basis of the irreducible tensor operator approach to solve Hamiltonian we have coded the software, BJMAG package, and performed the best-fit procedure for experimentally temperature variable magnetic susceptibilities for the complexes (1) and (2). The best-fit parameters were obtained as follows: lambda = -126 cm(-1), Delta = 432 cm(-1), kappa = 0.96, mJ' = 2.7 cm(-1) for the complex (1) and lambda = -165 cm(-1), Delta = 960 cm(-1), kappa = 0.95, J' = 9 cm(-1), mJ' = -0.1 cm(-1) for the complex (2). To further elucidate the individual role of each interaction in the employed model, the effects of the key factors governing the magnetic properties on temperature variable magnetic susceptibilities were examined in detail. The significance of the intercluster exchange interactions at low temperatures was briefly discussed and a self-consistent molecular field to calculate the thermally average spin of the nearest neighbor in the intercluster interaction was proposed. (C) 2009 Wiley Periodicals, Inc. Int J Quantum Chem 109: 3368-3378, 2009