Nine heteroleptic copper(I)/silver(I) complexes prepared from phosphine and diimine ligands: syntheses, structures and terahertz spectra

Abstract

Direct reactions under ambient conditions among copper/silver salts, diimine ligands and diphosphine ligands were carried out at different rations, generating nine novel Cu(I)/Ag(I) complexes, [Cu(Dpq)(dppp)](ClO4) (1), [Cu(Dppz)(dppp)](ClO4) (2), [Cu(Dpq)(POP)](ClO4) (3), [Cu(Dppz)(POP)](ClO4) (4), [Cu(Dpq)(xantphos)](ClO4)·0.843CH2Cl2 (5), [Cu(Dppz)(xantphos)](ClO4)·2CH2Cl2 (6), [Ag(Dpq)(xantphos)](ClO4) (7), [Ag(Dpq)(xantphos)](CF3SO3) (8), [Ag(Dpq)(POP)](CF3SO3) (9). {Dpq = pyrazino[2,3-f][1,10]phenanthroline, Dppz = dipyrido[3,2-a:2′,3′-c]phenazine, POP = 1,1′-[(Oxydi-2,1-phenylene)]bis[1,1-diphenylphosphine], xantphos = 9,9-dimethyl-4,5-bis(diphenylphosphanyl)xanthene, dppp = 1,3-bis(diphenylphosphine)propane). Their crystal structures have been determined by single crystal X-ray diffraction and they were characterized by IR, UV, elemental analysis, fluorescence spectra, 1H NMR and 31P NMR spectroscopy. All above nine Cu(I)/Ag(I) complexes have intriguing crystal stacking structures. Complexes 3, 9 are of 1D infinite chain structures formed by C–H⋯π interactions between each adjacent molecule while complexes 1, 2, 5, 6, 8 are of 2D network structures because of hydrogen bonds, C–H⋯π interactions and π⋯π interactions. However, complex 4 is complicated three-dimensional structure formed by C–H⋯π interactions. Some of the complexes exhibit obvious luminescence in the solid state, and interesting photoluminescence phenomenon are explained in detail. Among these six Cu(I) complexes, complex 5 shows the highest quantum yield up to 17.2%, which is due to the large steric hindrance of xantphos ligand. For these three Ag(I) complexes, complex 8 displays the highest quantum yield of 19.5%. In addition, the terahertz time-domain spectrum (THz-TDS) of these complexes has been investigated in detail leading to the preliminary discovery of correlation between terahertz spectra and crystal packing of complexes.