Luminescent Ir III –Au I Heterobimetallic Complex with a Carbene Bridging Ligand

Ir III –Au I luminescent bimetallic complexes have drawn growing interest for applications in photonics, catalysis, and biomedicine. Here, we report the synthesis of a new photoluminescent Ir III –Au I complex, the [(ppz) 2 Ir(μ-bbip)AuBr]PF 6, incorporating 1,3-dibenzyl-1H-imidazo[4,5- f ][1,10]phenanthrolin-3-ium bromide (bbip) as a bridging N -heterocyclic carbene (NHC) ligand. Among the various characterizations employed, single-crystal X-ray diffraction (SC-XRD) confirmed the structure of the complex, validating the proposed molecular formulation and coordination sphere. For comparative purposes and under similar conditions, the monometallic Ir III complex [Ir(ppz) 2 (bbip)](PF 6 ) 2 was synthesized and also validated by SC-XRD. Both complexes showed broad UV–vis excitation and orange-to-red emission in all tested solvents. Notably, the Ir III –Au I complex exhibited lower solvent polarity sensitivity than the mono-Ir III analog, with Au I coordination to bbip causing a slight emission blue shift. The incorporation of Au I significantly enhanced the photoluminescent properties, doubling both, the emission lifetime (τ) from 278 to 554 ns and the quantum yield (Φ) from 25 to 61% in degassed DCM. Notably, Φ remained high (30%) even in air-equilibrated DCM.