Development of metal complexes containing redox active ligands

Abstract

Transition metal complexes with 1,2-dithiolenes are a subject of high research interest as a consequence of their rich redox chemistry, versatility in the coordination modes, biological models1,2, as well as their well-known magnetic and electrical conducting properties. Dithiolene ligands have more than one resonant form: dianionic, radical monoanionic and neutral; and the oxidation state assignment of the metal is sometimes ambiguous in these complexes. For this reason, dithiolene ligands are considered as non-innocent. As expected, the dithione form is not feasible in aromatic dithiolenes. Bis(dithiolene) complexes possess an extended electronically delocalized core comprising the central metal, the four sulphurs and the carbon-carbon units.4 Delocalization can be further extended by functionalization of the ligand. This delocalization can lead to a number of important properties: Electrochemical behavior often which one or more reversible redox processes, Low energy absorption in the visible or NIR region, distribution of the frontier orbitals over much, or all, of the molecules. In most cases, a planar arrangement of the complex with a variety of central metals. Examples include Ni, Pd, Pt, Co, Fe, Au and Cu.  The large sulphur atoms compose part of the delocalized core and as such can mediate intermolecular interactions.