Organometallic photoreductants

Abstract

We have synthesized and fully characterized several tungsten arylisocyanide complexes, W(CNAr)_6, all of which exhibit intense metal-to-ligand charge transfer (MLCT) absorptions in the visible region of the spectrum. The lowest triplet excited state is emissive, with lifetimes ranging from 17 ns to 3.0 μs depending on the arylisocyanide ligand. A modular synthesis has been developed for tungsten oligoaryl isocyanide complexes whose triplet excited states, *W(CNAr)_6, are extremely powerful reductants: *W(CNAr)_6/[W(CNAr)6]+ potentials are near -2.7 V vs. Cp_2Fe/Cp_2Fe+. *W(CNAr)6 complexes rapidly reduce anthracene, benzophenone, and cobalticenium ion, thereby demonstrating that very challenging electron transfer reactions can be driven by these sensitizers. We are extending our work to include investigations of the photophysics and photochem. of closely related arylisocyanide complexes of chromium and molybdenum.