Upon photon absorption, polynuclear gold complexes undergo metal-centered excitation, resulting in long-lived triplets with an increasing coordination number. This feature facilitates direct binding with substrates in the inner coordination sphere. The formed exciplex can undergo inner-sphere electron transfer to reduce or oxidize molecules, even in cases where the redox potentials do not match.

Abstract

Photo-induced electron transfer is a fundamental step in photochemical reactions, where light energy is used to drive chemical transformations. However, conventional outer-sphere single electron transfer mechanisms encounter multiple limitations, notably requiring redox potential matching between photocatalysts and substrates, thereby impeding the activation of non-activated carbon-halogen bonds. In this concept review, we present an elucidation of the photophysical and photochemical properties exhibited by polynuclear gold photocatalysts, with a particular emphasis on their inner-sphere single electron transfer mechanism. By exploring these intricate aspects, we endeavor to furnish readers with a more profound insight into the remarkable potential of polynuclear gold photocatalysts and the indispensable role played by inner-sphere electron transfer in the realm of photocatalysis.