Synthesis, characterization, quantum chemical calculations and evaluation of antioxidant properties of 1,3,4-thiadiazole derivatives including 2-and 3-methoxy cinnamic acids

Abstract

A series of 1,3,4-thiadiazole derivatives including 2- and 3-methoxy cinnamic acids were synthesized, and their structures were elucidated by the UV, IR, H-1 NMR, C-13 NMR spectroscopies and elemental analysis. The UV and IR calculations of the molecules were performed by using B3LYP, HF and MP2 methods with selected 6-3++G(2d,2p), 6-311++G(3df,3pd) and cc-pvtz basis sets. Dipole moment, polarizability, chemical hardness/softness and electronegativity were also calculated and analyzed. Experimental FT-IR spectra and UV Vis spectrum of the compounds were compared with theoretical data. Furthermore, antioxidant activities of the compounds were practised via different test methods such as 2,2-diphenyl-1-picryl-hydrazyl (DPPH center dot), N,N-dimethyl-p-phenylenediamine (DMPD center dot+), and 2,2'azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS(center dot+)) scavenging activity assays. When compared with standards (BHA-Butylated hydroxyanisole, RUT-Rutin, and TRO-Trolox), it was observed that especially XIII and XIV which include methoxy groups at the o- and m-positions, respectively, had effective activities.