FT-IR, FT-Raman, ab initio and DFT structural and vibrational frequency analysis of 6-aminopenicillanic acid

Abstract

Quantum mechanical calculations of energies, geometries and vibrational wavenumbers of 6-aminopenicillanic acid were carried Out by using ab initio HF and density functional theory (DFT/B3LYP) methods with 6-311 G(d,p) basis set. The optimized geometrical parameters obtained by HF and DFT calculations are in good agreement with experimental X-ray data. A detailed interpretation of the infrared spectra has also been reported. The theoretical IR and Raman spectrograms have been constructed and compared with the experimental FT-IR and FT-Raman spectra. The differences between the observed and scaled wavenumber Values Of Most Of the fundamentals are very small. The thermodynamic parameters have also been Computed. (C) 2009 Elsevier B.V. All rights reserved.