Density functional theory studies on vibrational and electronic spectra of 2-chloro-6-methoxypyridine

The Fourier transform infrared (FTIR) and FT-Raman spectra of 2-chloro-6-methoxypyridine have been recorded in the range 3700–400 and 3700–100 cm−1, respectively. The complete vibrational assignment and analysis of the fundamental modes of the compound was carried out using the observed FTIR and FT-Raman data. The vibrational frequencies determined experimentally were compared with the theoretical frequencies computed by DFT gradient calculations (B3LYP method) employing the 6-31G(d,p), cc-pVTZ and/6-311++G(d,p) basis sets for the optimised geometry of the compound. The geometry and normal modes of vibration obtained from the DFT methods are in good agreement with the experimental data. The normal co-ordinate analysis was also carried out using DFT force fields utilising Wilson's FG matrix method. The influence of the substituents bulky chlorine atom and the methoxy group on the spectral characteristics of the compound has been discussed. The electronic spectrum determined by TD-DFT method is compared with the observed electronic spectrum.

The vibrational frequencies of 2-chloro-6-methoxypyridine determined experimentally were compared with the theoretical frequencies computed by DFT gradient calculations (B3LYP method) employing the 6-31G(d,p), cc-pVTZ and/6-311++G(d,p) basis sets for the optimised geometry of the compound. The electronic properties of the compound have been discussed.Figure optionsDownload as PowerPoint slideResearch highlights
► The complete vibrational assignment and analysis of the fundamental modes of 2-chloro-6-methoxypyridine was carried out using the observed FTIR and FT-Raman data.
► The vibrational frequencies determined experimentally were compared with the theoretical frequencies computed by DFT gradient calculations (B3LYP method) employing the 6-31G(d,p), cc-pVTZ and/6-311++G(d,p) basis sets for the optimised geometry of the compound.
► The electronic properties such as HOMO and LUMO energies were determined by time-dependent DFT (TD-DFT) approach, while taking solvent effect into account.
► The strong band system falling on the higher wavelength side with maximum at 254 nm is attributed to the most prominent π → π−* transitions.