Singlet, Doublet, and Triplet Emissions of Diarylamine-Modified Bismuth Pincer Complexes

We present six bismuth complexes (NC^RN)BiX₂ (X = Cl, I) with diarylamine-modified pincer ligands (NC^RN = (4-R-C₆H₄)₂N-C₆H₂-(CH₂NMe₂)₂-1,3; R = Me, O, NMe₂) and report on their optoelectronic, photophysical, and electrochemical properties. The complexes exhibit intriguing photophysical behavior, with the p-tolyl and p-anisyl derivatives showing phosphorescence at 77 K in frozen solvent matrices and at room temperature (r.t.) in the solid state. In THF solutions at r.t., only ligand-based fluorescence is observed with strongly reduced quantum yields compared to free proligands NCH^RN. Electrochemical studies reveal up to three reversible one-electron oxidations. The NMe₂-substituted complexes display the lowest oxidation potentials and the largest number of redox waves. Radical cations [NCH^NMe2N]⁺ and [(NC^NMe2N)BiX₂]⁺ are chemically stable and fluoresce weakly in the near-infrared (NIR) at ca. 1200 nm.