Thermal- and light-induced valence tautomerism with a concerted spin transition in an iron tris(diimine) complex

Abstract

The switching phenomena of spin crossover (SCO) and valence tautomerism (VT) are respectively dominated by iron(ii) and cobalt-dioxolene systems. To explore new possibilities for SCO or VT, the redox-active α-diimine ligand bis((phenyl)imino)acenaphthene (Ph-BIAN), which can adopt neutral (L0), monoanionic (L˙−), and dianionic (L2−) states, was paired with zinc, cobalt, manganese and iron to give [M(Ph-BIAN)3](BPh4)2 (M = Zn (1), Co (2), Mn (3), Fe (4)). Compounds 1, 2 and 3 adopt a temperature invariant MII-(L0)3 state, (2 and 3 are high spin (HS)) in the solid- and solution-states. Electrochemical measurements show the metal controls the degree of electronic communication between the Ph-BI..