Structural, Spectroscopic, and Chemical Properties of the First Low-Spin Iron(III) Semiquinonate Complexes in the Solid State and in Solution

Abstract

A strong antiferromagnetic coupling between the S=1/2 spin of the low-spin iron(III) ion and the S=1/2 spin of the coordinated semiquinonate radical ligand characterizes 1. Its solution chemistry and its solid-state properties were investigated by various spectroscopic and electrochemical methods as well as by structure analysis. The reactivities with molecular oxygen and superoxide anions rule out any involvement of the iron(III) semiquinonate complex in the mechanism of the reaction of molecular oxygen with iron(III) catecholate complexes, which serve as functional model complexes for intradiol-cleaving catechol dioxygenases.