Synthesis, Characterization, and Photophysical Properties of Heteroleptic Copper(I) Complexes with Functionalized 3-(2'-PyridyI)-1,2,4-triazole Chelating Ligands

A new series of mononuclear copper(I) complexes. (1, 9) with functionalized 3-(2'-pyridyl)-1,2,4-triazole chelating ligands, as well as the halide and/or phosphine ancillary ligands, have been synthesized. Complexes 1-9 were fully characterized by elemental analysis, NMR spectroscopy, mass spectroscopy, electronic absorption spectroscopy, fluorescence spectroscopy, cyclic voltammetry, and X-ray crystallography (1-8). They adopt a distorted tetrahedral configuration, and are considerably air stable in solid state and in solution. All these Cu(I) complexes display a comparatively weak low energy absorption in CH2Cl2 solution, assigned to charge transfer transitions with appreciable MLCT character, as supported by TD-DFT studies. Cu(I) :halide complexes 1-4 each shows bright solid-state emission at room temperature, although they are nonemissive in fluid solutions, in which the emission markedly depends on the halide and the substituent on the 2-pyridyl ring. Complexes 5-9 bearing 2-Pyridyl functionalized 1,2,4-triazole and phosphine exhibit good photoluminescence properties in solution. and solid states at ambient temperature, which are well modulated via the alteration of the auxiliary phosphine ligand. and the structural modification of 3-(2'-pyridyl)-1,2,4-triazole. Interestingly, cationic complex 6 and neutral derivative 7 can readily be interconverted through the ring inversion of the 1,2,4-triazolyl regulated by the NH <-> N- transformation.