New bis 1,3,4-oxadiazole derivatives: syntheses, characterizations, computational studies, and antioxidant activities

Abstract

In this study, two new bis oxadiazole derivatives (2a and 2b) were synthesized. The new compounds were characterized by elemental analyses, IR, 1H NMR, 13C NMR, and mass spectral studies and were tested for their antioxidant activity. According to the results, it was observed that the synthesized compounds (2a and 2b) had a very high activity in both 2,2-diphenyl-1-picrylhydrazyl (DPPH) and ferric reducing ability of plasma (FRAP) tests. The approximate geometries of the compounds 2a and 2b were prepared with GaussView5 visualization program. The optimized molecular geometric parameters, vibrational wavenumbers, UV–vis parameters, and HOMO–LUMO simulations were computed using Gaussian 09W program. The computations were performed at 6-311++G(d,p) basis set using the B3LYP functional in density functional theory (DFT) method. The harmonic vibrational wavenumbers computed in gas phase were scaled with 0.958 (1700–4000 cm−1) and 0.983 (0–1700 cm−1) for the B3LYP/6-311++G(d,p) level. To calculated the UV–vis spectroscopic parameters with TD-DFT method, the compounds 2a and 2b were optimized in DMF and DMSO solvents using the integral equation formalism polarizable continuum model (IEFPCM) method at the B3LYP/6-311++G(d,p) level. The HOMO, LUMO, and UV–vis analyses were studied to interpret intramolecular charge transfers.