Investigation of cobalt (1,10-phenanthroline)-bis-(3,6-di-tert-butyl-o-benzosemiquinolate) by X-ray diffraction, IR and ESR spectroscopy, magnetochemistry, and precision calorimetry

The bistable cobalt complex containing two symmetrical 3,6-di-tert-butyl-o-benzoquinone and one 1,10-phenanthroline moieties as ligands (1) was synthesized. Complex 1 was isolated in the individual state and characterized by IR and ESR spectroscopy, X-ray diffraction, magnetochemical studies, and precision calorimetry. A change in temperature causes the reversible metal-ligand electron transfer and spin crossover (redox isomerism) in complex 1 in the crystalline state. The redox-isomeric transformation at ∼250 K is accompanied by the phase transition. The structural study at two temperatures confirmed the changes in the molecular and crystal structure associated with the redox-isomeric transformation.