Switching to green: green-light hydrosilylation photocatalysis with metalla-N-heterocyclic carbene complexes

We recently reported the first green-light-driven photocatalytic system for alkyne hydrosilylation utilizing platinum(II)-metallaNHC complexes (Chem. Eur. J. 2024, 30(65), e202403264). Featuring an elegant, atom-efficient synthesis and outstanding efficiency at an unprecedentedly low loading of 0.01 mol%, these complexes represent a superior, sustainable alternative to traditional transition-metal photocatalysts. Chemical tuning of the these complexes was achieved using rational design by starting from the original blue-light-operating platinum(II)-metallaNHC phtocatalysts (Chem. Commun., 2018, 54, 9450-9453).

By combining various experimental methods—including UV-Vis and emission spectroscopy alongside cyclic voltammetry—with advanced theoretical analyses such as DFT/TD-DFT and IFCT, we rationalized their exceptional photocatalytic properties through photo-induced charge transfer within the extended condensed system. Specifically, the amino-functionalized photocatalysts exhibit remarkably high positive excited-state reduction potentials and sufficiently long triplet-state lifetimes. These electronic features provide robust oxidative capabilities in the photoexcited state, enabling highly efficient participation in bimolecular electron-transfer reactions that successfully outcompete deleterious non-radiative deactivation pathways.

Building upon these insights, our group is currently investigating the broader utility of these innovative metallaNHC complexes in other photocatalytic transformations. We are particularly focused on exploiting their strong oxidative capabilities and long-lived excited states to develop highly controlled, light-driven polymerization protocols, expanding the scope of green-light photoredox catalysis in macromolecular synthesis.