Combined experimental and theoretical studies on the vibrational spectra of 2-quinolinecarboxaldehyde

Combined experimental and theoretical studies have been performed on the structure and vibrational spectra (IR and Raman spectra including far region) of 2-quinolinecarboxaldehyde. Hartree–Fock (HF) and density functional B3LYP calculations have been employed with the 6-311++G(d,p) basis set for investigating the structural and spectroscopic properties of two possible aldehyde rotamers of 2-quinolinecarboxaldehyde. When the O atom of the aldehyde is farther away than the nitrogen atom of the quinoline, 2-quinolinecarboxaldehyde has the lowest possible energy, and thus is in its ground state. The computed vibrational frequencies of this lowest energy rotamer agree also slightly better than those of the higher energy rotamer with the experimental frequencies after the computed frequencies are scaled.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Frequencies and geometries of the possible two conformers of 2-quinolinecarboxaldehyde were calculated. ► The HF and B3LYP results were compared with experimental FT-IR, FT-FIR, and FT-Raman data. ► The conformational analysis of 2-quinolinecarboxaldehyde was performed.