Chelating di(N-heterocyclic carbene) complexes of iridium(III): Structural analysis, electrochemical characterisation and catalytic oxidation of water

Abstract

The synthesis of novel iridium(III) complexes of general formula [IrClCp∗(diNHC)](PF6), with chelating di(N-heterocyclic carbene) ligands (diNHC) is reported. The obtained complexes differ for the wingtip substituents at the nitrogen atom of the heterocycles (Me, t-Bu, Cy, n-oct), the linker between the carbene donors (-CH2-, -CH2CH2-, -CH2CH2CH2-) and for the type of heterocyclic rings (imidazole and benzimidazole). The new complexes have been characterised in solution with NMR spectroscopy, ESI-MS spectrometry and cyclic voltammetry and, in the solid state, by single crystal X-ray structure analysis. These techniques allow to evaluate the influence of the dicarbene ligand on the electronic properties of the metal centre. The complexes have been successfully tested as water oxidation catalysts using Ce(IV) as chemical oxidant.