Observing the Entry Events of a Titanium‐Based Photoredox Catalytic Cycle in Real Time

Abstract

AbstractTitanium‐based catalysis in single electron transfer (SET) steps has evolved into a versatile approach for the synthesis of fine chemicals and first attempts have recently been made to enhance its sustainability by merging it with photo‐redox (PR) catalysis. Here, we explore the photochemical principles of all‐Ti‐based SET‐PR‐catalysis, i.e. in the absence of a precious metal PR‐co‐catalyst. By combining time‐resolved emission with ultraviolet‐pump/mid‐infrared‐probe (UV/MIR) spectroscopy on femtosecond‐to‐microsecond time scales we quantify the dynamics of the critical events of entry into the catalytic cycle; namely, the singlet‐triplet interconversion of the do‐it‐all titanocene(IV) PR‐catalyst and its one‐electron reduction by a sacrificial amine electron donor. The results highlight the importance of the PR‐catalyst's singlet‐triplet gap as a design guide for future improvements.