Synthesis, crystal structure and magnetic studies of tetranuclear hydroxo and ligand bridged [Co4(μ3-OH)2(μ2-dea)2(L–L)4]4Cl·8H2O [L–L = 2,2′-bipyridine or 1,10-phenanthroline] complexes with mixed valence defect dicubane core

Abstract

X-ray crystallography of the title complexes indicates a discrete mixed valence (Co₂^II–Co₂^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.