Synthesis, characterization and computational studies of three α-amino-phosphonic acids derivatives from Meta, Ortho and Para aminophenol

•Three α-aminophosphonic acids were synthesized from three aminophenol isomers.•The possible optimized geometric structures of mAPac, oAPac and pAPac were researched.•FT-IR spectroscopic properties of the synthesized α-aminophosphonic acids were examined by experimental and theoretical methods.•HOMO and LUMO energies, MEP distribution of the molecule were calculated.•Thermodynamic parameters were determined.

In this paper, we report first, the synthesis of three α-aminophosphonic acids from Meta-aminophenol, Ortho-aminophenol and Para-aminophenol. Then, we present a detailed DFT study based on B3LYP/6-31G (d, p) of geometrical structures and electronic properties of these compounds. The vibrational frequencies determined experimentally were compared with DFT gradient calculations which were obtained theoretically employing the B3LYP/6-31G (d, p) basis set method for the optimized geometry of the compound. The vibrations obtained from DFT method were found in good agreement with the experimental data. The study was extended to the HOMO-LUMO analysis to calculate the energy gap (Δ), Ionization potential (I), Electron Affinity (A), Global Hardness (η), Chemical Potential (μ) and Global Electrophilicity (ω). The calculated HOMO and LUMO energy reveals shows that the charge transfers occurring within the molecule. On the basis of vibrational analyses, the thermodynamic properties of the titles compound were also calculated.