Antioxidant activity of new synthesized imine and its corresponding α-aminophosphonic acid: Experimental and theoretical evaluation

•New Schiff base and its corresponding α-aminophosphonate acid have been synthesised.•Antioxidant activities have been evaluated using the DPPH radical scavenging method.•A computentional DFT study of the antioxidant activity has been carried out.•Comparative experimental and computentional studies have been performed.•Global reactivity and Fukui indices have been calculated. A Schiff base (I1) and its corresponding α-aminophosphonic acid (P1) were synthesized using a simple and rapid preparation method and with a chemical yield of up to 75% and 68%, respectively. The structures of I1 and P1 were experimentally characterized by IR, 1H NMR, 13C NMR and 31P NMR spectroscopic methods. A test of their antioxidant activities was carried out and indicated that I1 and P1 were able to scavenge the DPPH radical. The main objective of this research was the theoretical study of the antioxidant power of I1 and P1. Density functional theory (DFT) calculations at the B3LYP/6-311+G(d, p) level were performed to determine BDE, PA, ETE, IP, PDE, spin density distribution parameters and HOMO-LUMO energies in order to study the antioxidant potential of the title products in the gas phase. According to the theoretical results, the abstraction of H atoms from the 2-OH and 1-OH groups of I1 and P1 compounds, respectively, is most preferable during the free radical scavenging process. In addition, it was shown that HAT is the thermodynamically dominant mechanism compared to SPLET and SET-PT. The calculated data of the antioxidant activity of I1 and P1 are consistent with the experimental results. A study of the chemical reactivity of these molecules was carried out. Calculations of the global parameters (chemical potential (μ), hardness (η), softness (S) and electrophilicity index (ω)) and Fukui indices of the studied compounds were done and discussed. These molecules have an electrophilic character. The Fukui functions were calculated to specify the interaction sites of these products. [Display omitted]