Abstract

Recently, phosphonate compounds have got immense attention of the scientific community due to their structural properties. These are inserted in a number of chemical moieties and are associated with important pharmacological activities. Herein, we reported synthesis of the imino phosphonate compounds: (E)-diethyl (3-nitrobenzylideneamino)(phenyl)methylphosphonate (DNBMP), (E)-diethyl (4-hydroxybenzylideneamino) (phenyl) methyl phosphonate) (DHBMP), and (E)-diethyl (4-nitrobenzylideneamino)(phenyl)methylphosphonate (DNPMP) with high yields form the condensation reaction of diethyl (α-aminobenzyl)phosphonate hydrochloride and the corresponding substituted benzaldehyde. The synthesized compounds were analyzed by various spectroscopic techniques such as NMR, MS, UV–Vis, and IR spectroscopy. Moreover, the computational studies were also performed and the experimental and theoretical investigation results were compared. The geometries of the compounds were optimized with B3LYP/6-311+G (d,p) and absence of imaginary frequency confirmed the stability of DNBMP, DHBMP and DNPMP. The FT-IR, natural bond orbital (NBO) analysis, frontier molecular orbitals (FMOs) and nonlinear (NLO) properties of DNBMP, DHBMP, and DNPMP were performed with former level of theory. In addition, UV–Vis spectra were obtained by Time Dependent Density Functional Theory (TD-DFT) approach with former level in Polarizable Continuum Model (PCM) using different solvents. A comparative investigation of FT-IR and UV–Visible spectra of DNBMP, DHBMP and DNPMP revealed that there is a good agreement between DFT and experimental findings. NBO analysis was employed to calculate the atomic charges as well as bonding interactions of the interesting molecules. NBO findings revealed that non-bonding interactions might be one of the most important reasons for stability of DNBMP, DHBMP and DNPMP. Moreover, the energy value of HOMO/LUMO was found to be −6.977/-3.033 eV with ΔE 3.944 eV (DNBMP), −6.300/-1.274 eV with ΔE 5.026 eV (DHBMP) and −6.993/-3.124 eV with a band gap (ΔE) 3.869 eV (DNPMP) and global reactivity parameters (GRP) were also obtained using the HOMO-LUMO energies. It was observed that DNBMP, DHBMP and DNPMP have greater NLO responses than standard molecules.