The spectroscopic investigation of 3-amino-2-pyrazinecarboxylicacid and methyl-3-amino-2-pyrazinecarboxylate - A Comparative Study

The FTIR and FT-Raman spectra of 3-amino-2-pyrazinecarboxylicacid (APC) and methyl-3-amino-2-pyrazinecarboxylate (MAPC) have been recorded in the region 4000-400 cm-1 and 3500-100 cm-1, respectively. The optimized geometry, frequency and intensity of the vibrational bands of the compounds were obtained by the density functional theory using 6-311++G(d,p) basis set. The harmonic vibrational frequencies were calculated and the scaled values have been compared with experimental FTIR and FT-Raman spectra. The observed and the calculated frequencies are found to be in good agreement. A detailed interpretation of the infrared and Raman spectra were also reported based on potential energy distribution (PED). 1H and 13C NMR spectra were recorded and its corresponding nuclear magnetic resonance chemical shifts of the molecule were also calculated using the gauge independent atomic orbital (GIAO) method. UV-Visible spectrum of these compounds was recorded and the electronic properties HOMO and LUMO energies were measured by TD-DFT approach. The calculated HOMO and LUMO energies show that charge transfer occurs within the molecule. Furthermore, molecular electrostatic potential was performed. Molecular stability and bond strength were investigated by applying the natural bond orbital analysis (NBO).