Structural analysis and investigation of molecular properties of Cefpodoxime acid, a third generation antibiotic

Extensive quantum mechanical studies are carried out on Cefpodoxime acid (CA), a new generation drug by Hartree–Fock (HF) and B3LYP methods to understand the structural and spectral characteristics of the molecule. The most stable geometry of the molecule was optimized and the bond parameters were reported. The spectroscopic properties of this pharmaceutically important compound were investigated by FT-IR, FT-Raman, UV and 1H NMR techniques. The scaled vibrational frequencies of CA in the ground state are calculated by HF and B3LYP methods with 6–311++G (d, p) basis set and compared with the observed FT-IR and FT-Raman spectra. The vibrational spectral analysis indicates the presence of two intra molecular hydrogen bonds in the molecule which is supported by theoretical study. 1H NMR chemical shifts (δ) were calculated for the CA molecule and compared with the experimental values. The theoretical electronic absorption spectral data in water and ethanol solvents were computed by TD-DFT method. UV–Vis absorption spectra of CA are recorded in these two solvents and compared with theoretical spectra. The spectral data and natural bond orbital (NBO) analysis confirm the occurrence of intra molecular interactions in CA. The electronic distribution, in conjunction with electrophilicity index of CA was used to establish the active site and type of interaction between CA and beta lactamases. Mulliken population analysis on atomic charges is also carried out and thermodynamic properties of the title compound are calculated. [Display omitted] •Structural analysis of Cefpodoxime acid is done extensively by experimental and theoretical studies.•The intra-molecular delocalization in the molecule is established by NBO analysis.•Two intra molecular hydrogen bonds are identified theoretically in the optimized structure of CA.•The thermodynamic functions ZPVE, thermal energies, Cv, S, H and dipole moment of CA are computed.•The electronic distribution and electrophilicity index are used to identify the active drug action site in CA.