Synthesis and Characterization of Three New Emissive Mononuclear CuI Heteroleptic Complexes with Functionalized 6-Cyano-2,2′-bipyridine Chelating Ligands

A new series of luminescent mononuclear CuI complexes with functionalized 6-cyano-2,2′-bipyridine chelating ligands, [Cu(xantphos)(cbpy)]ClO4 (1), [Cu(xantphos)(4,4’-Me2cbpy)]ClO4·CH2Cl2·H2O (2), and [Cu(POP)(cbpy)]ClO4·CH2Cl2 (3) (xantphos=4,5-bis(diphenylphosphino)-9,9-dimethylxanthene; POP=bis(2-diphenylphosphinophenyl)ether; 4,4’-Me2cbpy=4,4’-dimethyl-6-cyano-2,2′-bipyridine; cbpy=6-cyano-2,2′-bipyridine) have been successfully prepared, and their structures and photophysical properties are investigated. Single crystal structures of the three complexes reveal a distorted tetrahedral coordination geometry around the CuI centres with the P atoms of diphosphane ligands and N donors of 2,2′-bipyridine ring. Luminescence measurements indicate that these CuI complexes display good emission properties both in the solution and solid states at room temperature, which can be well modulated through modifying the structure of 6-cyano-2,2′-bipyridine. It is shown that the introduction of two electron-donating methyl groups at the 4,4’-positions of the 6-cyano-2,2′-bipyridine is favourable to enhance the luminescence properties of the CuI complexes.