Synthesis, characterization, and luminescence properties of mononuclear copper(I) halide complexes of 2-(2-benzimidazolyl)-6-methylpyridine.

Three new mononuclear copper(I) halide complexes of 2-(2-benzimidazoly)-6-methylpyridine (Hbmp), [Cu(Hbmp)(PPh3)X] (X = I (1); Br (2); Cl (3)), have been synthesized and structurally characterized by X-ray crystallography. It is revealed that the most significant impact of the auxiliary halide ligand on the structure is on the Cu一Npyridyl and Cu一P bond lengths. Complexes 1–3 show a weak low-energy absorption band at 350–600 nm in CH2Cl2, ascribed to the Cu(I) to Hbmp metal-to-ligand charge-transfer (MLCT) transitions, perhaps mixed with some halide-to-ligand charge-transfer (XLCT) character. The solid-state emissions of 1–3 are observed at ambient temperature, markedly depending on the halide ancillary ligand bound to the {Cu(Hbmp)(PPh3)} unit, which are assigned to the MLCT excited states with some mixing of the XLCT characters. [ABSTRACT FROM AUTHOR]