Spin Crossover in an Iron(II) Complex with a Radical Iminosemiquinonate Ligand

Abstract

Abstract Metal complexes that exhibit spin crossover (SCO) or valence tautomerism (VT) are promising candidates for molecular materials. In an exploration of the interplay between SCO and VT in iron chemistry, we combined redox-active aminophenol derivatives (4,6-di-tert-butylphenol (H2LH) or 2-anilino-4,6-di-tert-butylphenol (H2LPh)) with iron to prepare: [FeII(HLPhAP)−(tpa)]BPh4 (1), [FeII(LPhISQ)•–(tpa)]BPh4 (2), [FeII(HLHAP)−(tpa)]BPh4 (3), and [FeIII(LHISQ)•–(tpa)](BPh4)2 (4) (tpa = tris(2-pyridylmethyl)amine). The aminophenol derivatives were found to adopt either closed-shell monoanionic aminophenolate (HLAP)− or open-shell monoanionic radical iminosemiquinonate (LIS..