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

The reaction of a triazole ligand, 2-(1 H -1,2,3-triazol-4-yl)pyridine (L1), with 2-bromopyridine afforded three new ligands, 2,2'-(1 H -1,2,3-triazole-1,4-diyl)dipyridine (L2), 2,2'-(2 H -1,2,3-triazole-2,4-diyl)dipyridine (L3) and 2,2'-(1 H -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 4 ) [ n = 1, P^P = (PPh 3 ) 2 (1); n = 1, P^P = POP (2); n = 2, P^P = (PPh 3 ) 2 (3); n = 2, P^P = POP (4); n = 3, P^P = (PPh 3 ) 2 (5); n = 3, P^P = POP (6); n = 4, P^P = (PPh 3 ) 2 (9); n = 4, P^P = POP (10)] have been obtained from the reaction of Ln with [Cu(MeCN) 4 ]ClO 4 in the presence of PPh 3 and POP. L3 was also found to form dinuclear compounds [Cu 2 (L3)(PPh 3 ) 4 ](ClO 4 ) 2 (7) and [Cu 2 (L3)(POP) 2 ](ClO 4 ) 2 (8). All of the Cu(I) compounds have been characterized by IR, UV/vis, CV, 1 H NMR, and 31 P{ 1 H} NMR. The molecular structures of 1-3, 5, and 7 have been further determined by X-ray crystallography. In CH 2 Cl 2 solutions, these Cu(I) complexes exhibit tunable green to orange emissions (563-621 nm) upon excitation at λ ex = 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).