Towards controlling the valance tautomer interconversion character by solvation

Abstract

Valence tautomers[1] are bi-stable functional molecular materials in which it is observed charge transference between redox active ligands and a metallic center followed by the change of spin of the metal[2], induced by external stimuli such as illumination[3] and/or changes in temperature and pressure[ 4 ]. Valence tautomerism (VT) interconversion is essentially entropically driven, associated with remarkable variations in optical and/or magnetic properties, and can be modulated with slight chemical changes. Typical examples of VT compounds are coordination compunds of Co and o-dioxolenes ligands[5]. Crystalsof complex [Co III (SQ)(Cat) (4-NO 2 -py) 2 ] (I), where py= pyridine, Cat = 3,5-di-tbutylcatecholate and SQ=3,5-ditbutylsemiquinonate, were first studied with respect to low spin (LS) to high spin (HS) thermo and photoinduced conversion. It was reported that I become HS