Synthesis, DFT Calculations to Investigate the Electronic Structure, Absorption Electronic Spectra, Antimicrobial Activity Application, and Non-Linear Optical Analysis of Pyridinyl and Pyrimidinyl Phosphonates Schemes

In this study, the structure optimized and calculations of the electronic properties for the study of two compounds which are 2 is Diethyl {5-[(2-hydroxy-5-methylphenyl) carbonyl] -2-thioxo-1,2,3,4-tetrahydropyrimidin-4-yl}-phosphonate (2), compound 4 is Diethyl {6-amino -1-(4-chlorophenyl) -5-cyano-3- [(2-hydroxy-5-methylphenyl)carbonyl] -1,2- dihydropyridin-2-yl]}phosphonate (4) have been performed by using the DFT method at the B3LYP/6-311++G (d, p) theory level. UV-Vis spectra, in both methanol and dioxane solvents, have been employed for two compounds 2 and 4 by density functional time-dependent theory (TD-DFT) calculations at the same level of calculation. The method of Coulomb-attenuating (CAM-B3LYP) and Corrected Linear Response Polarizable Continuum Model (CLR) PCM studied for theoretically obtaining the absorption electronic spectra in the gas phase, methanol, and dioxane, respectively; indicate a good agreement with the observed spectra and FT-IR, vibrational spectra were calculated. The GIAO method calculated the 1H and 13C NMR chemical shifts theoretically values which reflect better coincidence with the experimental chemical shifts. The dihedral angles result of calculations shows that two compounds 2 and 4 are non-planar. The stability of the two compounds 2 and 4, the hyper conjugative interactions, and the delocalization of the atomic charges was analyzed with the Natural Orbital Bond analysis (NBO). The relocation of electronic density and electronic structures were discussed. Studied functional density local descriptors, (MEP) Molecular Electrostatic Potential, molecular border orbitals, and absorption spectral. Analysis of the global descriptors revealed that compound 4 is the most reactive with an energy difference between the border orbital of ΔEgap = 3.605 eV. Furthermore, this compound 4 is the less stable, the softest, and has the greatest electronic exchange capacity of the other compound 2 studied. Studied by DFT calculations (SAR) structure-activity relationship and contacted with practical antimicrobial results for compounds 2 and 4.