Absorption and luminescence spectra of 5-aryl-3-methyl-1,2,4-oxadiazoles and their chelate complexes with Zinc(II) and copper(II)

Abstract

5-(2-Hydroxyphenyl)-3-methyl-1,2,4-oxadiazole and its O-methyl and O-acyl derivatives, as well as zinc(II) and copper(II) chelates, were synthesized. All these compounds showed luminescence with the emission maxima ranging from λ = 332 to 490 nm, but only 5-(2-methoxyphenyl)- and 5-(2-acetoxyphenyl)-3-methyl-1,2,4-oxadiazoles and zinc(II) complex of 5-(2-hydroxyphenyl)-3-methyl-1,2,4-oxadiazole were characterized by high luminescence quantum yield (φ = 0.308–0.452, 0.089–0.153, and 0.115–0.334, respectively). Stable conformers of 5-(2-hydroxyphenyl)-3-methyl-1,2,4-oxadiazole with different structures of the coordination entity were identified by DFT quantum chemical calculations.