Comparative and DFT antioxidant studies of phenolic group substituted pyridine-based azo derivatives.

Two azo compounds 2-(3-pyridylazo)-3,5-dihydroxybenzoic acid () and 4-(3-pyridylazo)resorcinol () thought to have the potential to be used as antioxidants were designed, synthesized and antioxidant activities were investigated both and . The synthesized compounds were characterized by H-NMR, C-NMR, FT-IR, UV-Vis and mass spectra. The molecular geometry and vibrational frequency calculations of the synthesized compounds in ground state were performed by the density functional theory (DFT) employing B3LYP level with the 6-311 G(d,p) basis set. The gauge independent atomic orbital (GIAO) method was used to determine the chemical shift values of H-NMR and C-NMR. HOMO-LUMO calculations were carried out by time-dependent DFT (TD-DFT) approach. Computational spectroscopic data of the synthesized compounds are fully compatible with experimental ones. The antioxidant activities of the and were investigated by using DPPH assay. It was determined that the molecule showed better antioxidant activity than and, butylated hydroxytoluene (BHT) which is the standard antioxidant. In addition, the thermodynamic stability parameters obtained with the help of DFT calculations were found to be quite compatible with the antioxidant capacity sequence derived from the DPPH assay. HighlightsTwo pyridine derivative azo compounds were synthesized and evaluated for its antioxidant activityMolecular geometry and spectroscopic properties of the molecules were calculated and antioxidant activities were investigated by DPPH free radical scavenging assayThe PAB molecule showed better antioxidant activity than BHTCommunicated by Ramaswamy H. Sarma.