Vibrational spectroscopic investigation of free and coordinated 5-aminoquinoline: The IR, Raman and DFT studies (original) (raw)
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Chemical Physics, 2005
The solid phase FTIR and FT-Raman spectra of 2,4-diaminoquinazoline and 4-amino-2-methylquinoline have been recorded in the regions 4000-50 and 3500-100 cm À1 , respectively. The spectra were interpreted with the aid of normal coordinate analysis following full structure optimization and force field calculations based on density functional theory using standard B3LYP/6-31G* and B3LYP/6-311 + G** methods and basis set combinations and was scaled using various scale factors yielding fairly good agreement between observed and calculated frequencies. Based on the present good quality scaled quantum mechanical force field, a reliable description of the fundamentals was provided and the assignments have been proposed with the aid of normal coordinate analysis. The infrared and Raman spectra were also predicted from the calculated intensities. Comparison of the simulated spectra with the experimental spectra provides important information about the ability of the computational method to describe the vibrational modes.
Central European Journal of Chemistry, 2007
The geometry, frequency and intensity of the vibrational bands of 8-hydroxyquinoline and its 5,7-dichloro, 5,7-dibromo, 5,7-diiodo and 5,7-dinitro derivatives were obtained by the density functional theory (DFT) calculations with Becke3-Lee-Parr (B3LYP) functional and 6-31G* basis set. The effects of chloride, bromide, iodide and nitro substituent on the vibrational frequencies of 8-hydroxyquinoline have been investigated. The assignments have been proposed with aid of the results of normal coordinate analysis. The observed and calculated spectra are found to be in good agreement.
Vibrational Spectroscopy, 2008
The molecular structure, vibrational frequencies and the corresponding vibrational assignment of Zn(biq)X 2 (X = Cl and Br; biq = 2,2 0biquinoline) have been studied by employing the hybrid density functional theory (B3LYP) method and the complete basis set (DFT) method together with the 6-31G(d,p) basis set for X = Cl and Br. The FT-IR (400-4000 cm À1) and Raman (100-3200 cm À1) spectra of compounds were recorded and compared with that of the calculated spectra, which allowed authors to assign most of the observed bands. It was demonstrated that cis conformer is suitable for the Zn(biq)X 2 compounds. The fundamental vibrational modes were characterized by their total energy distribution. The coordination effects on vibrational wavenumbers of biq were discussed in detail.
Quantum Chemical and Spectroscopic Investigations of 5-quinolinamine
2010
The Fourier transform infrared (FTIR) and FT-Raman spectra of 5-aminoquinoline (5AQ) have been recorded in the range 4000-400 and 3500-100 cm −1 , respectively. The complete vibrational assignment and analysis of the fundamental modes of the compounds were carried out using the observed FTIR and FT-Raman data. 1 H and 13 C nuclear magnetic resonance (NMR) chemical shifts of the molecule were calculated by using the gauge independent atomic orbital (GIAO) method. UV-vis spectrum of the compound was recorded and the electronic properties, such as HOMO and LUMO energies, were performed by time-dependent DFT (TD-DFT) approach. The geometric parameters, chemical shifts and absorption wavelengths were compared with the experimental data of the molecule. The vibrational frequencies which were determined experimentally are compared with those obtained theoretically from ab initio HF and DFT-B3LYP gradient calculations employing the 6-31G** and 6-311++G** basis sets for optimized geometries of the compound. The interactions of NH-and the influence of amino group on the skeletal modes are investigated.
Journal of Raman Spectroscopy, 2009
phenylquinazolin-4(3H)-one were recorded and analyzed. The vibrational wavenumbers of the title compound were computed using HF/6-31G * and 6-311G * basis sets and compared with experimental data. The assignments of the normal modes are done by potential energy distribution (PED)calculations. The prepared compound was identified by nuclear magnetic resonance (NMR) and mass spectra. Optimized geometrical parameters of the title compound are in agreement with reported structures.
Tautomerism of 4-hydrazinoquinazolines: vibrational spectra and computational study
Vìsnik Dnìpropetrovsʹkogo Unìversitetu: Serìâ Hìmìâ, 2014
The tautomerism of 4-hydrazinoquinazoline and its derivatives was investigated. Geometry and thermodynamic parameters were computed theoretically using Gaussian 03 software. All calculations were performed at the MP2 level of theory using the standard 6-31G(d) basis. Energetics and relative stabilities of tautomers were compared and analyzed in a gas phase. The effect of solvents (1,4-dioxane, acetic acid, ethanol and water) on the tautomeric equlibria was evaluated using PCM. It was determined that solvents induced slight changes in the relative stability. In all cases 4-hydrazinoquinazoline exists predominantly as the amino form. The variation of dipole moments was studied. The anharmonic vibrational wavenumbers for unsubstituted 4-hydrazinoquinazoline were calculated at MP2/6-31G(d) level and compared with experimental data. The modes of IR spectra were assigned. The calculated herein wavenumbers and intensities of amino form are in good agreement with those observed experimentally.
Vibrational spectroscopic study of some quinoline derivatives
Vibrational Spectroscopy, 2016
This work deals with the successful synthesis, spectroscopic properties (Raman and infrared) and theoretical calculations of some quinoline derivatives, namely 4-azido-7chloroquinoline and the commercially available 4,7-dichloroquinoline, quinolin-8-ol. The analysis of the Raman and infrared spectra of the quinoline derivatives, supported by DFT calculations, for the first time has afforded the opportunity to characterize unambiguously the main vibrational bands for these important molecules, which are mainly used as anti-malaria compounds. Despite the very similar structures of these quinolines the Raman and infrared spectra exhibit significant wavenumber shifts for several key bands. A characteristic band at ca. 1580 cm-1 can be assigned involving a δ(OH) mode for quinolin-8-ol (QNO) as well as the band at ca. 1090 cm-1 attributed to δ(CCl) for 4,7-dichloroquinoline (DCQN). The compound 4-azido-7-chloroquinoline (ACQN) shows a very characteristic marker band at ca. 1300 cm-1 , which has been assigned to the ν(NN) mode of the azide group.
Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy, 2014
FT-IR, FT-Raman and (1)H NMR spectra of 4-hydroxy-2-oxo-1,2-dihydroquinoline-8-carboxylic acid were recorded and obtained data were confronted with the computed using Gaussian09 software package. DFT/B3LYP, B3PW91 calculations have been done using 6-31G* and SDD basis sets, to investigate the vibrational frequencies and geometrical parameters. The assignments of the normal modes are done by potential energy distribution (PED) calculations. The calculated first hyperpolarizability is comparable with the reported values of similar quinoline derivatives and is an attractive object for future studies of non-linear optics. The stability of the molecule arising from hyperconjugative interaction and charge delocalization has been analyzed using NBO analysis. MEP predicts the most reactive part in the molecule. The calculated (1)H NMR results are in good agreement with experimental data.