Luminescence properties of copper(I), zinc(II) and cadmium(II) coordination compounds with picoline ligands

Abstract

Mononuclear coordination compounds of copper(I) – [Cu(PPh3)2(picoline)(NO3)], zinc(II) – [ZnCl2(picoline)2] (picoline=3– and 4–methylpyridine) and polymeric cadmium(II) – [CdCl2(β-picoline)2]n were prepared and their luminescence properties in solid state and acetonitrile solutions were determined. Single crystal X-ray crystallography revealed distorted tetrahedral geometry around the central ions of the compounds. The compounds exhibit green photoluminescence in solid state and in acetonitrile solutions. The emission of copper(I) compounds originated from metal-to-ligand charge transfer state combined with nitrato-to-picoline charge transfer state i.e. (1(M+X)LCT). The presence of nitrato ligand in the coordination sphere of copper(I) compounds quenches the emission. Luminescence of zinc(II) and cadmium(II) compounds results from chloride-to-picoline charge transfer state and the quantum efficiency in the case of the polymeric Cd(II) compound reaches 39%. The photoluminescence quantum yields of the mononuclear zinc(II) compounds vary from 10 to 16% depending on the conditions (solid state, solution).