A computational perspective on equilibrium geometry, vibrational spectra and electronic structure of antioxidant active Mannich base 1-[(Pyridin-2-yl amino) methyl] pyrrolidine-2,5-dione

Abstract

The 1-[(pyridin-2-yl amino) methyl] pyrrolidine-2,5-dione (SFAP) is a class of organic Mannich base system which has been identified for its effective performance in favor of antioxidant activity. An intensified vibrational analysis has been carried out for SFAP by comparing the experimental FT-IR and FT-Raman spectra with computed IR and Raman spectra. The feasible tautomeric forms were generated and the most stable tautomer was compared with experimental crystal structure of SFAP. 1H and 13C NMR spectral analysis were assisting on determining structure property relationship via chemical shifts and magnetic shielding effects of title compound. The natural bond orbital (NBO) analysis provides insight on bonding, anti-bonding behavior and its nature in hybridization. The frontier molecular orbital approach suggests the nature of intra molecular charge transfer and the participation of individual moieties and atoms in SFAP. The trend of thermodynamic properties such as enthalpy, entropy and heat capacity of SFAP at different temperature were derived and related in the manner of quadratic equation. The Molecular Electrostatic Potential (MEP) imprint in relation with different charges such as atomic polar tensor (APT), electrostatic potential (ESP), Hirshfeld, natural bond orbital analysis (NBO), Mulliken were interpreted. The magnitude of charge was compared to find probable electrophilic and nucleophilic reactive sites in SFAP. All the theoretical calculations were performed at HF/6-31+G/6-311++G(d,p), B3LYP/6-31+G/6-311++G(d,p) model chemistry.