Polypyridine Iridium(III) and Ruthenium(II) Complexes for Homogeneous and Graphene-Supported Photoredox Catalysis

Iridium(III) and ruthenium(II) polypyridyl based photocatalysts have been prepared and their structure determined using H-1 NMR, HR-MS and single crystal XRD. Their spectroscopic and electrochemical properties have been studied by UV-vis absorption, emission spectroscopy and cyclic voltammetry. These complexes have been used as photoredox homogeneous catalysts in an intramolecular cyclization model reaction in which they show high activity. They have been covalently anchored on graphene oxide (GO) via an esterification reaction and non-covalently fixed on reduced graphene oxide (rGO) via pyrene moieties. Heterogenized complexes exhibit good photocatalytic activities and, interestingly, the use of a pyrene-derivatized Ir(III) terpyridine-based complex highlights an unexpected "on/off" effect of the photocatalytic activity triggered by the presence or absence of rGO.