.Solid solutions of redox-isomeric bis-o-semiquinonato cobalt complex with zinc, nickel and manganese compounds having the same composition

Bis-o-semiquinonato cobalt complex (2,2 '-bpy)Co(3,6-DBSQ)2 (1) is known to be redox-isomeric (valence tautomeric), i. e. undergo reversible ligand-metal electron transfer accompanied with spin crossover of metal ion under external excitation (2,2 '-bpy - 2,2 '-bipyridine; 3,6-DBSQ - 3,6-di-tert-butyl-o-benzosemiquinone). The using of one pot reaction allowed us to obtain the number of solid solutions of cobalt complex 1 with similar complexes (2,2 '-bpy)M(dioxolene)2 of M = zinc (2), M = nickel (3) and M = manganese (4) in the ratios 1:1 and 1:5 (dioxolene = redox forms of 3,6-di-tert-butyl-o-benzosemiquinone). Composition of solid solutions was established by X-ray spectral microanalysis and confirmed by magnetic measurements. The metals ratio taken into reaction is well reproduced in solid solution. Crystal structures of solid solutions were established by single crystal X-ray diffraction study. X-ray diffraction pattern allows to observe the superpositions of two structures. Variable temperature magnetic susceptibility measurements show that magnetizations of solid solutions are additive and are composed of magnetizations of both complexes. Redox-isomeric transformation occurs in all solid solutions independently of their compositions. The dilution of redox-isomeric compound 1 by inert components 2 and 3 (with zinc and nickel complexes) results in diminishing of transition temperature whereas the dilution by manganese compound does not affect the transition temperature. The reason of this result is proposed to be the maximal difference in molecules volumes (which is determined by ionic radii and charge distributions between metal and ligands) in cobalt/zinc and cobalt/nickel pairs being compared to cobalt/manganese one.