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

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)1(ClO4) (2), [Cu(Dpq)(POP)](ClO4) (3), [Cu(Dppz)(POP)](ClO4) (4), [Cu (Dpq)(xantphos)](ClO4).0.843CH(2)Cl(2) (5), [Cu(Dppz)(xantphos)](ClO4)center dot 2CH(2)Cl(2) (6), [Ag(Dpq)(xantphos)] (ClO4) (7), [Ag(Dpq)(xantphos)](CF3SO)(3) (8), [Ag(Dpq)(POP)1(CF3SO3) (9). (Dpq = pyrazino[2,3-f][1,10] phenanthroline, Dppz = dipyrido[3,2-a:2',3'-clphenazine, 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, H-1 NMR and P-31 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 center dot center dot center dot pi interactions between each adjacent molecule while complexes 1, 2, 5, 6, 8 are of 2D network structures because of hydrogen bonds, C-H center dot center dot center dot pi interactions and pi center dot center dot center dot pi interactions. However, complex 4 is complicated three-dimensional structure formed by C-H center dot center dot center dot pi 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. (C) 2019 Elsevier Ltd. All rights reserved.