Controlling the Photofunctionality of a Polyanionic Heteroleptic Copper(I) Photosensitizer for CO2 Reduction Using Its Ion‐pair Formation with Polycationic Ammonium in Aqueous Media

Abstract A water‐soluble trianionic heteroleptic copper(I) photosensitizer having four sulfonate groups ( CuPS 3− ) was found to afford the 1 : 2 ion‐pair adduct with dicationic alkylammonium (hexamethonium) cations ( HM 2+ ) in aqueous media, leading to exhibit excellent photophysical and photocatalytic performances owing to the substantial suppression of water‐derived non‐radiative decay of the photoexcited state.