Synthesis, structure and photoluminescence of Cu(I) complexes containing new functionalized 1,2,3-triazole ligands.

The reaction of a triazole ligand, 2-(1-1,2,3-triazol-4-yl)pyridine (L1), with 2-bromopyridine afforded three new ligands, 2,2'-(1-1,2,3-triazole-1,4-diyl)dipyridine (L2), 2,2'-(2-1,2,3-triazole-2,4-diyl)dipyridine (L3) and 2,2'-(1-1,2,3-triazole-1,5-diyl)dipyridine (L4). A series of luminescent mononuclear copper(I) complexes of these ligands [Cu(Ln)(P^P)](ClO) [ = 1, P^P = (PPh) (1); = 1, P^P = POP (2); = 2, P^P = (PPh) (3); = 2, P^P = POP (4); = 3, P^P = (PPh) (5); = 3, P^P = POP (6); = 4, P^P = (PPh) (9); = 4, P^P = POP (10)] have been obtained from the reaction of Ln with [Cu(MeCN)]ClO in the presence of PPh and POP. L3 was also found to form dinuclear compounds [Cu(L3)(PPh)](ClO) (7) and [Cu(L3)(POP)](ClO) (8). All of the Cu(I) compounds have been characterized by IR, UV/vis, CV, H NMR, and P{H} NMR. The molecular structures of 1-3, 5, and 7 have been further determined by X-ray crystallography. In CHCl solutions, these Cu(I) complexes exhibit tunable green to orange emissions (563-621 nm) upon excitation at = 380 nm. In the solid state, these complexes show intense emissions and it is interesting to note that 1 and 3 are blue-light emitters. Density functional theory (DFT) calculations revealed that the lowest energy electronic transition associated with these complexes predominantly originates from metal-to-ligand charge transfer transitions (MLCT).