Air-Stable Blue Phosphorescent Tetradentate Platinum(II) Complexes as Strong Photo-Reductant

Abstract

Strong photo‐reductants have applications in photo‐redox organic synthesis involving reductive activation of C−X(halide) and C=O bonds. We report herein air‐stable PtII complexes supported by tetradentate bis(phenolate‐NHC) ligands having peripheral electron‐donating N‐carbazolyl groups. Photo‐physical, electrochemical, and computational studies reveal that the presence of N‐carbazolyl groups enhances the light absorption and redox reversibility because of its involvement into the frontier MOs in both ground and excited states, making the complexes robust strong photo‐reductant with E([Pt]+/*) over −2.6 V vs. Cp2Fe+/0. The one‐electron reduced [Pt]− species are stronger reductants with EPC([Pt]0/−) up to −3.1 V vs. Cp2Fe+/0. By virtue of the strong reducing nature of these species generated upon light excitation, they can be used in light‐driven reductive coupling of carbonyl compounds and reductive debromination of a wide range of unactivated aryl bromides.