Spectral investigation and theoretical study of zwitterionic and neutral forms of quinolinic acid
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Date
2015
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Abstract
In this study, molecular structure and vibrational analysis of quinolinic acid (2,3-pyridinedicarboxylic acid), in zwitterionic and neutral forms, were presented using FT-IR, FT-Raman, NMR, UV experimental techniques and quantum chemical calculations. FT-IR and FT-Raman spectra of 2,3-pyridinedicarboxylic acid (2,3-PDCA) in the solid phase were recorded in the region 4000-400 cm-1 and 3500-0 cm-1, respectively. The geometrical parameters and energies were obtained for zwitter and neutral forms by using density functional theory (DFT) at B3LYP/6-311++G(d,p) level of theory. 3D potential energy scan was performed by varying the selected dihedral angles using M06-2X and B3LYP functionals at 6-31G(d) level of theory and thus the most stable conformer of the title compound was determined. The most stable conformer was further optimized at higher level and vibrational wavenumbers were calculated. Theoretical vibrational assignment of 2,3-PDCA, using percentage potential energy distribution (PED) was done with MOLVIB program. 13C and 1H NMR spectra were recorded in DMSO. Chemical shifts were calculated at the same level of theory. The UV absorption spectra of the studied compound in ethanol and water were recorded in the range of 200-400 nm. The optimized geometric parameters were compared with experimental data. © 2015 Elsevier B.V. All rights reserved.
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Keywords
Chemical analysis , Dihedral angle , Molecular physics , Nuclear magnetic resonance spectroscopy , Potential energy , Pyridine , Quantum chemistry , Ultraviolet spectroscopy , Water absorption , DFT , Experimental techniques , FT-Raman , FTIR and FT-Raman spectra , Nmr and uv spectrum , Potential energy distribution , Quantum chemical calculations , Vibrational wavenumbers , Density functional theory