Dinuclear cobalt bis(dioxolene) complex exhibiting two sequential thermally induced valence tautomeric transitions

4,6-Di-2'-pyridylpyrimidine is employed as a bis(diimine) ligand bridging two cobalt bis(dioxolene) centers. The thermally induced valence tautomeric transitions of these two metal centers are coupled through the ligand. The result is that sequential switching from high-spin Co(II) to low-spin Co(III) of one center, followed by the onset of switching of the other center at lower temperature, is observed in a solid amorphous thin film by IR absorption spectroscopy.