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

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 Pt-II 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 -2.6V vs. Cp2Fe+/0. The one-electron reduced [Pt](-) species are stronger reductants with E-PC([Pt](0/-)) up to -3.1V 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.