Abstract
A series of heteroleptic copper(I) complexes of the type [Cu(bpg)(P-P)]PF6 (1-4) have been synthesized where bpg = [4b,5,7,7a-tetrahydro-4b,7a-epiminomethanoimino-6H-imidazo[4,5-f] [1,10]-phenanthroline-6,13dione] and P-P are phosphine derived ancillary ligands (triphenyl phosphine (PPh3), 1,2 bis(diphenylphosphino)ethane (dppe), bis[(2-diphenylphosphino)phenyl]ether (POP) and 1,3 bis(diphenylphosphino)propane (dppp)). All copper(I)-phosphine complexes were thoroughly characterized by elemental analyses, IR, H-1 NMR, C-13 NMR,P- 31 NMR and ESI-MS, UV-visible, emission spectroscopy and DFT calculations. The crystal structure of 1 contains two Cu(I) molecules in asymmetric unit which localizes in distorted tetrahedral geometry with N2P2 coordination core. The UV-visible spectra indicated that ancillary phosphine ligands significantly affect the MLCT band of the copper(I) complexes. The bands in the UV-visible spectra fit well with the TD-DFT calculations and are assigned to the contribution of HOMO-2 -> LUMO, HOMO-1 -> LUMO and HOMO -> LUMO orbitals. These Cu(I) complexes exhibit green emission in CH2Cl2 at room temperature with emission wavelengths at 545-572 nm. Cyclic voltammetric data revealed that steric hindrance of diphosphine ligands affected the oxidation potential of Cu(I) complexes.