Tuning the Excited‐state Properties of Cyclometalated Platinum (II) Complexes of 6‐Phenyl‐2,2′‐bipyridine by Ancillary Acetylide Ligand

A series of luminescent cyclometalated platinum (II) complexes, (CNN)Pt(CC) [HCNN = 4-(4-tolyl)-6-phenyl-2,2′-bipyridine; R = 4-chlorophenyl (1), phenyl (2) and 4-tolyl (3)], were synthesized, and their spectroscopic properties have been examined. These complexes are brightly emissive both in fluid solution and in the solid state, attributed to triplet metal-to-ligand charge transfer (3MLCT) state. The excited state energy can be tuned by ancillary acetylide ligands. The emission lifetimes in dichloro-methane solution at room temperature were up to 1.64 μs and the emission quantum yields were in the range of 0.03–0.15.