The emergence of photoredox catalysis over the last decade has facilitated small molecule activation under mild reaction conditions with minimal equipment overheads. This synthetic approach exploits the ability of predominantly homogenous d6 transition metal complexes to absorb visible-light and generate an excited state capable of single-electron transfer (SET) reactions that either donate an electron to, or remove an electron from, simple organic substrates. Research efforts typically focus on the development of new synthetic methodologies, with often only a cursory investigation of the fundamental light-dependent interactions. This work presents a unique photoredox reaction cycle comprised of two photoactive iridium(III) complexes working together. Following the first photoinduced electron transfer (PET) between the off-the-shelf catalyst [Ir(ppy)2(dtb-bpy)]+ and a sacrificial donor, subsequent reactions generate a previously unknown species distinguished by reduction and semi-saturation of the ancillary ligand. Rigorous structural characterization confirmed the nature of this new highly reducing metal complex and spectroscopic measurements demonstrated the PET properties of its excited state. Turnover of this new photocatalytic cycle occurs along with the reformation of [Ir(ppy)2(dtb-bpy)]+. These observations were rationalized by a mechanism containing two distinct yet interconnected photoredox cycles that provide access to an extended potential window. Understanding the photochemical properties of this new metal complex help to both rationalize fringe cases of unexpected reactivity as well as expand the potential synthetic utility of this system. The application of this newly discovered photocatalytic cycle in other synthetic transformations will also be presented.

Opening a can of glow-worms: Tandem photoredox catalysis of [Ir(ppy)2(dtb-bpy)]+

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.