Vibrational spectroscopy (FTIR and FTRaman) investigation using ab initio (HF) and DFT (B3LYP and B3PW91) analysis on the structure of 2-amino pyridine

The FTIR and FTRaman spectra of 2-amino pyridine (2-AP) molecule have been recorded using Bruker IFS 66 V spectrometer in the range of 4000–100 cm−1. The molecular geometry and vibrational frequencies in the ground state are calculated by using the ab initio Hartree–Fock (HF) and DFT (B3LYP and B3PW91) methods with 6-31++G (d, p) and 6-311++G (d, p) basis sets. The computed values of frequencies are scaled using a suitable scale factor to yield good coherence with the observed values. Making use of the recorded data, the complete vibrational assignments are made and analysis of the observed fundamental bands of molecule is carried out. The geometries and normal modes of vibrations obtained from ab initio HF and B3LYP/B3PW91 calculations are in good agreement with the experimentally observed data. The differences between the observed and scaled wave number values of most of the fundamentals are very small in B3LYP than HF. The influence of N atom and amine group in the skeletal ring vibrations of the title molecule has also been discussed.