Tailoring Gold Corroles via Regioselective Nitration: Near Infrared Emission, Singlet Oxygen Sensitization, and Photocatalytic Oxidation of Sulfides

A regioselective nitration at the β-positions of gold(III) corrole has been developed using the nitrosonium ion as a nitrating reagent, constituting the earliest reported example of gold(III) corrole nitration. The mechanism underlying this nitration process has also been elucidated. The reaction proceeds via the formation of a one-electron oxidized, [(corrolato^<b>•</b>2-)Au^III]^<b>•</b>+ species. Which has been characterized by UV-vis, EPR, and DFT calculations. The incorporation of two nitro groups into the bipyrrole unit of the corrole markedly enhances the electron-withdrawing character of the corrole ligand, resulting in a pronounced upshift in both oxidation and reduction potentials of the corresponding metal complex compared to its non-nitrated analogs. The 3,17-dinitro-corrolato-gold(III) complex is best described as exhibiting partial inverse hypercorrole character, with the lowest-energy transition involving partial corrole-to-nitro charge transfer. The synthesized compounds display near-infrared phosphorescence under ambient conditions, with emission maxima red-shifted to ∼920 nm in the nitrated gold(III) corrole. They exhibit ∼50% singlet oxygen sensitization quantum yields and catalyze selective sulfide oxidation to sulfoxides under ambient conditions with air and light as cofactors. It shows a broad substrate scope, achieving over 99% selectivity and a TON of 1300-1800, outperforming many literature examples by preventing sulfone formation.