Synthesis, crystal structure and magnetic studies of tetranuclear hydroxo and ligand bridged [Co_4(μ_3-OH) _2(μ_2-dea)_2(L-L)_4] 4Cl·8H_2O [L-L = 2,2′-bipyridine or 1,10-phenanthroline] complexes with mixed valence defect dicubane core

摘要

X-ray crystallography of the title complexes indicates a discrete mixed valence (Co_2 II-Co_2 III) defect dicubane molecular unit where each cobalt nucleus attains a distorted octahedral geometry. The α-diimine (L-L) chelator coordinated to each cobalt ion stops further polymerization or nuclearization. The water molecules in the lattice play a crucial role in the formation of the supramolecular architectures. Magnetic data were analyzed using the effective spin-1/2 Hamiltonian approach and the parameters are, J = 115(6) K, ΔJ = -57.0(1.2) K, g_(xy) = 3.001(25), and g_z = 7.214(7) for 1 and J = 115(12) K, ΔJ = -58.5(2.5) K, g_(xy) = 3.34(5), and g_z = 6.599(12) for 2 suggesting that only the g matrices are prone to the change of α-diimine chelator.