Abstract
We have prepared the (5-chloro-quinolin-8-yloxy) acetic acid and characterized it by using infrared, Raman and multi-dimensional nuclear magnetic resonance spectroscopies. 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. Three stable conformations of the compound were theoretically determined in 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 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. Besides, the force constants of the three conformers of (5-chloro-quinolin-8-yloxy) acetic acid were calculated and compared with those obtained by us for the 2-(quinolin-8-yloxy) acetic acid. In addition, the characteristics of the electronic delocalization of those structures were performed by using natural bond orbital (NBO), while the corresponding topological properties of electronic charge density are analysed by employing Bader’s atoms in molecules theory (AIM).
Highlights
Heterocyclic compounds that contain the moiety exhibit a wide range of biological properties [1,2,3,4,5], such as the 2-(quinolin-8-yloxy) acetohydrazones that have antiamoebic activities [5] for which, the structural and vibrational study of these types of compounds are of great chemical and pharmaceutical importance
A complete vibrational analysis of all observed bands in the vibrational spectra of 2-(quinolin8-yloxy)-acetic acid [6] was performed by means of the density functional theory (DFT) calculations combined with Pulay’s scaled quantum mechanical force field (SQMFF) methodology [7,8,9]
As in 2-(quinolin-8-yloxy)-acetic acid [6], the higher NPA charges observed on the O17 and O22 atoms in the CII structure justified the repulsion between those atoms
Summary
Heterocyclic compounds that contain the (quinolin-8yloxy) moiety exhibit a wide range of biological properties [1,2,3,4,5], such as the 2-(quinolin-8-yloxy) acetohydrazones that have antiamoebic activities [5] for which, the structural and vibrational study of these types of compounds are of great chemical and pharmaceutical importance. A complete vibrational analysis of all observed bands in the vibrational spectra of 2-(quinolin8-yloxy)-acetic acid [6] was performed by means of the DFT calculations combined with Pulay’s scaled quantum mechanical force field (SQMFF) methodology [7,8,9]. We have synthesized and characterized the compound and the optimized geometries and frequencies for the normal modes of vibration of CQA considering three different stable structures were calculated in order to carry out a complete assignment of all observed bands in the infrared and Raman spectra. The nature of the different rings and bonds of the three studied structures of (5-chloro-quinolin-8-yloxy) acetic acid were analyzed by means of the NBO studies [10,11,12] while the topological properties of electronic charge density were determined employing the Bader’s atoms in molecules theory (AIM) [13]
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