Synthesis and structural and vibrational analysis of (5,7-dichloro-quinolin-8-yloxy) acetic acid

We have prepared the (5,7-dichloro-quinolin-8-yloxy) acetic acid and characterized it by infrared and Raman spectroscopies in the solid phase and by nuclear magnetic resonance (NMR) spectroscopy in a CDCl3 solution. The density functional theory (DFT) together with the 6-31G* and 6-311++G** basis sets were used to study its structure and vibrational properties. Two stable conformations of the compound were theoretically determined in the gas phase and probably these conformations are present in the solid phase. The harmonic vibrational wavenumbers for the optimized geometries were calculated at the same theory levels. For a complete assignment of all the observed bands in the vibrational spectra the DFT calculations were combined with Pulay’s scaled quantum mechanical force field (SQMFF) methodology in order to fit the theoretical wavenumber values to the experimental ones. The force constants for the (5,7-dichloro-quinolin-8-yloxy) acetic acid were calculated and compared with those obtained for the (5-chloro-quinolin-8-yloxy) acetic acid and 2-(quinolin-8-yloxy)-acetic acid compounds. Furthermore, the characteristics of the electronic delocalization, the topological properties of the electronic charge density together with the highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) energy gaps were studied.

► The compound was synthesized and characterized by IR, Raman and NMR spectroscopies.
► Two stable conformers for the DQA in gas phase were determined by B3LYP calculations.
► A complete theoretical assignment of the spectral features is proposed.
► The two Cl atoms in the quinoline ring increase the reactivity of the molecule.
► The NBO and AIM analysis confirm the NH bonds in the both DQA conformers.