Ferroverdin: cation variation and recognition of isomerictris chelate geometries by iron oxidation states

Abstract

Synthetic ferroverdins, NaFe¹¹(RQ₎₃ afford trinuclear M[Fe(RQ)₃]₂ upon reaction with bivalent ions (M²⁺). A probable bonding mode is considered. Ferric ions oxidise ferroverdin to ferriverdin, Fe^III(RQ)₃. Both fac and mer isomers can be observed for ferro- and ferriverdins but at equilibrium the preferred isomers are fac for ferro- and mer for ferriverdin. Mismatch in geometry with oxidation state gets spontaneously corrected by isomerisation. Equilibrium constants, isomerisation rates, redox potentials and EPR spectra are examined. A study on the pattern of isomer population as a function of oxidation for other 3d analogues of ferro- and ferriverdin is initiated.