Experimental and theoretical spectroscopic studies, HOMO–LUMO, NBO and NLMO analysis of 3,5-dibromo-2,6-dimethoxy pyridine

The molecular vibrations of 3,5-dibromo-2,6-dimethoxy pyridine (DBDMP) have been investigated in polycrystalline sample, at room temperature, by Fourier transform infrared (FT-IR) and FT-Raman spectroscopies. The vibrational frequencies of the fundamental modes of the compound have been precisely assigned and theoretical results were compared with the experimental vibrations. Theoretical information on the optimized geometry, harmonic vibrational frequencies, infrared and Raman activities were obtained by means of ab initio and density functional theory (DFT) gradient calculations, using 6-311++G(d,p) basis set. Thermodynamic properties like entropy, heat capacity and zero point energy have been calculated for the molecule. HOMO-LUMO energy gap has been calculated. The intramolecular contacts have been interpreted using Natural Bond Orbital (NBO) and Natural Localized Molecular Orbital (NLMO) analysis. The Molecular Electrostatic Potential (MEP) analysis reveals the sites for electrophilic attack and nucleophilic reactions in the molecule.

Graphical abstractThe molecular vibrations of 3,5-dibromo-2,6-dimethoxy pyridine (DBDMP) have been investigated by FT-IR and FT-Raman spectroscopies. The vibrational frequencies of the fundamental modes of the compound have been precisely assigned and theoretical results were compared with the experimental vibrations. Thermodynamic properties have been calculated for the molecule. HOMO–LUMO energy gap has been calculated. The intramolecular contacts have been interpreted using Natural Bond Orbital (NBO) and Natural Localized Molecular Orbital (NLMO) analysis. The Molecular Electrostatic Potential (MEP) analysis reveals the sites for electrophilic attack and nucleophilic reactions in the molecule.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► The FT-IR and FT-Raman spectra of the title compound have been recorded. ► Optimized geometry, vibrational frequencies, IR and Raman intensities are obtained. ► The HOMO and LUMO energies have been calculated. ► Stability of the molecule has been analyzed using NBO and NLMO analysis.