Synthesis and Luminescent Properties of Copper(I) Complexes with 3-Pyridin-2-yl-5-(4-R-phenyl)-1H-1,2,4-Triazoles

A series of heteroligand copper(I) complexes with 3-pyridin-2-yl-5-(4-R-phenyl)-1H-1,2,4-triazoles (R = H, CH3, CH3O) and PPh3 of general composition CuIL(PPh3) have been synthesized and studied. The compounds have been characterized by elemental analysis, IR spectroscopy, and diffusion reflectance spectra. The structure of the complex with 3-pyridin-2-yl-5-phenyl-1H-1,2,4-triazole has been determined by single-crystal X-ray diffraction analysis. The complex is mononuclear and has a tetrahedral environment of the central atom. The compounds exhibit strong visible photoluminescence (lambda(max) = 599-609 nm). Quantum-chemical calculations at the B3LYP/DGDZVP level have demonstrated that the short phosphorescence life-time of the CuIL(PPh3) compounds is caused by intensity transfer from the S-0-S-2 transition through spinorbit coupling induced by the rotation of the iodine 5p orbital upon the T-1-S-2 transition.