Mono- and bimetallic Ir(iii) based catalysts for the homogeneous photocatalytic reduction of CO2 under visible light irradiation. New insights into catalyst deactivation

Abstract

Mononuclear iridium(III) complexes [Ir(mppy)(tpy)X] (mppy = 4-methyl-2-phenylpyridine, X = Cl, I) and binuclear analogues with various bis(2-phenylpyridin-4-yl) bridging ligands were synthesized and characterized by their spectroscopic and electrochemical properties. Kinetic measurements concerning the photocatalytic two electron reduction of CO₂ to CO were investigated in order to determine the influence of intermolecular interactions between two active centers. A detailed comparison between the monometallic and the bimetallic complexes indicates an enhanced lifetime (TON) of the covalently linked complexes, causing an increased overall conversion of CO₂. Additionally the deactivation pathways of the catalysts are examined.