Cu-F Interactions between Cationic Linear N-Heterocyclic Carbene Copper(I) Pyridine Complexes and Their Counterions Greatly Enhance Blue Luminescence Efficiency.

A series of easily accessible linear N-heterocyclic carbene (NHC) copper(I) complexes, bearing pyridine (py) and its derivatives as chromophore ligands, are barely emissive in the single-crystalline solid state. However, their powders, neat films, and dilute doped films of poly(methyl methacrylate) (PMMA; 1-10%) show very intense blue-to-blue-green photoluminescence with remarkable quantum yields φ of up to 87% and microsecond lifetimes, indicative of triplet states being involved. These luminescence properties are similar to trigonal coordinated NHC copper(I) bis(pyridine) complexes, which we have also isolated and characterized with respect to their structures and photophysics.