Synthesis of new azo schiff bases of pyrazole derivatives and their spectroscopic and theoretical investigations

Abstract

New pyrazole Schiff bases containing azo groups, 4-((E)-phenyldiazenyl)-3-(4-nitrobenzylidene)-1-phenyl-pyrazole-5-amine and its series, were synthesized using the condensation reaction between p-nitrobenzaldehyde and (E)-1-phenyl-4-(phenyldiazenyl)-1H-pyrazole-3,5-diamine in the molar ratio of 1:1. The compounds were characterized using IR, UV–Vis, 1H-NMR and 13C-NMR spectroscopies. The UV–Vis spectral data were obtained in ethanol, chloroform, N,N-dimethylformamide (DMF), DMF (pH = 2) and DMF (pH = 12), which have different polarity and pH values. Meanwhile, the experimental spectral analyses were supported by the theoretical calculations based on the density functional theory (DFT) using the B3LYP/cc-pvtz level. Structural analyses, vibrational frequencies, UV, and NMR calculations were performed at the same level of the theory. In addition, via using HOMO-LUMO energies, the electrochemical quantities such as chemical hardness and electronegativity were calculated and analyzed. © 2018 Elsevier B.V.