Syntheses,steric hindrance effects,luminescent properties and TD-DFT calculations for a series of copper(I) iodide coordination complexes

A series of copper(I) coordination complexes, CuI(Phen)2-(Dpp)bp] (1) (Phen?=?phenanthroline, 2-(Dpp)bp?=?2-(Diphenylphosphino)-biphenyl), Cu₂I₂(Phen)2-(Dpp)bp] (2), CuI(2-PBI)2-(Dpp)bp] (3) and (2-PBI?=?2-(pyridin-2-yl)-1H-benzod]imidazole) and CuI(Bipy)2-(Dpp)bp] (Bipy?=?2,2′-bipyridine) (4) have been synthesized. X-ray crystal structure studies revealed that complexes 1, 3 and 4 showed mononuclear structures with the copper atoms coordinated by iodide, a chelating nitrogen-donor ligand, and a monodentate phosphine ligand. However, the coordination centers display different distortions of their tetrahedral geometries, according to the steric hindrance of the bulky phosphine ligands. Complex 2 has a dinuclear structure, with trigonal and tetrahedral coordination centers. Variations in the aromatic system of the N-heterocyclic ligands result in different luminescence properties. Thus, the emission maxima for these complexes range from 580 to 642 nm, with lifetimes of τ?=?0.6–0.9 and 1.6–4.2 μs. TD-DFT calculations reveal the origin of the luminescence to be metal–ligand charge transfer, as well as halogen–ligand charge transfer. The optical absorption spectra and thermal stabilities of the complexes have also been studied.