NMR Parameters and Vibrational Investigation of 2-Dicyanovinyl-5-（4-ethoxyphenyl） thiophene by ab initio HF and DFT Calculations

Optimized geometry and harmonic vibrational frequency of 2-dicyanovinyl-5-(4- ethoxyphenyl)thiophene (C16H12N2OS) are calculated at the HF/6-31++G(d,p) and B3LYP/6- 311++G(d,p) levels. Mulliken charges in the ground state are also calculated. The research shows the presence of intermolecular interaction in the title compound. The scaled harmonic vibrational frequencies have been compared with experimental FT-IR spectra. A detailed interpretation of the infrared spectra of the title compound is reported. The theoretical spectrograms for IR spectra of the title compound have been constructed. The isotropic chemical shift computed by 13C and 1H NMR analyses also shows good agreement with the experimental observations.     

FT-IR, FT-Raman spectra and quantum chemical calculations of 3,4-dimethoxyaniline

In this work, we will report a combined experimental and theoretical study on molecular and vibrational structure of 3,4-dimethoxyaniline (3,4-DMA). The Fourier transform infrared and Fourier transform Raman spectra of 3,4-DMA was recorded in the solid phase. The optimized geometry was calculated by HF and B3LYP methods using 6-31G(d,p) and 6-311++G(d,p) basis sets. The harmonic vibrational frequencies, infrared intensities, Raman scattering activities and the thermodynamic functions of the title compound were performed at and HF/B3LYP/6-311++G(d,p) level of theories. The scaled theoretical wavenumber showed very good agreement with the experimental values. A detailed interpretation of the infrared and Raman spectra of 3,4-DMA was reported. The theoretical spectrograms for IR and Raman spectra of the title molecule have been constructed.     

Molecular structure, vibrational spectra and NBO analysis of phenylisothiocyanate by density functional method

The molecular geometry, vibrational frequencies and NBO analysis of phenylisothiocyanate (PITC) in the ground state have been calculated by using density functional theory calculation (B3LYP) with 6-311++G(d,p) basis set. The optimized geometrical parameters obtained by DFT calculations are in good agreement with experimental values. Comparison of the observed fundamental vibrational frequencies of the PITC and calculated result by density functional theory (B3LYP) indicates B3LYP is superior for molecular vibrational problems. The entropy of the title compound was also performed at HF/B3LYP/6-311++G(d,p) levels of theory. Natural bond orbital (NBO) analysis of title molecule is also carried out. A detailed interpretation of the IR and Raman spectra of PITC is reported on the basis of the calculated potential energy distribution (PED). The theoretical spectrogram for IR spectrum of the title molecule has been constructed.     

Comparison of experimental and ab initio HF and DFT vibrational spectra of benzimidazole

In this work, we will report a combined experimental and theoretical study on molecular and vibrational structure of benzimidazole. The laser Raman and Fourier transform infrared spectra of benzimidazole were recorded in the solid phase. The equilibrium geometry, harmonic vibrational frequencies, infrared intensities, Raman scattering activities, depolarization ratios and reduced masses were calculated by HF and density functional B3LYP method with the 6-311G(d,p) basis set. The scaled theoretical wavenumbers showed very good agreement with the experimental values. The thermodynamic functions of the title compound were also performed at HF/6-31G(d,p)/6-311G(d,p) and B3LYP/6-31G(d,p)/6-311G(d,p) levels of theory. A detailed interpretations of the infrared and Raman spectra of benzimidazole is reported. The theoretical spectrograms for FT-IR spectra of the title molecule have been constructed.     

Vibrational spectroscopy investigation using ab initio and density functional theory analysis on the structure of 2-amino-5-methylphenol

The laser Raman and Fourier transform infrared spectra of 2-amino-5-methylphenol were recorded in the solid phase. The equilibrium geometry, harmonic vibrational frequencies, infrared intensities, Raman scattering activities, depolarization ratios and reduced masses were calculated by HF and density functional B3LYP methods by using 6-311+G(d,p) basis set. The scaled theoretical wavenumbers showed very good agreement with the experimental values. The thermodynamic functions of the title compound were also performed at HF/6-31G(d,p)/6-311+G(d,p) and B3LYP/6-31G(d,p)/6-311+G(d,p) levels of theory. A detailed interpretations of the infrared and Raman spectra of 2-amino-5-methylphenol is reported. The theoretical spectrograms for FT-IR spectra of the title molecule have been constructed.     

Molecular structure, vibrational spectroscopic, first-order hyperpolarizability and HOMO, LUMO studies of 2-aminobenzimidazole

In the present work, we reported a combined experimental and theoretical study on molecular structure, vibrational spectra and HOMO-LUMO analysis of 2-aminobenzimidazole (2-ABD). The FTIR (400-4000 cm(-1)) and FT-Raman spectra (50-3500 cm(-1)) of 2-ABD were recorded. The molecular geometry, harmonic vibrational wavenumbers and bonding features of 2-ABD in the ground-state have been calculated by using the density functional B3LYP method with 6-311++G(d,p) and 6-31G(d) as basis sets. The energy and oscillator strength were calculated by time-dependent density functional theory (TD-DFT) result complements with the experimental findings. The calculated HOMO and LUMO energies showed that charge transfer occurs within the molecule. Finally, the calculation results were applied to simulate infrared and Raman spectra of the title compound which showed good agreement with the observed spectra.     

Vibrational spectroscopy investigation using ab initio and density functional theory analysis on the structure of 3-(6-benzoyl-2-oxobenzo[d]oxazol-3(2H)-yl)propanoic acid

The molecular structure, vibrational frequencies and infrared intensities of the 3-(6-benzoyl-2-oxobenzo[d]oxazol-3(2H)-yl)propanoic acid were calculated by the HF and DFT methods using 6-31G(d) basis set. The FT-infrared spectra have been measured for the title compound in the solid state. We obtained 11 stable conformers for the title compound, however the Conformer 1 is approximately 3.88 kcal/mol more stable than the Conformer 11. The comparison of the theoretical and experimental geometry of the title compound shows that the X-ray parameters fairly well reproduce the geometry of the Conformer 1. The harmonic vibrations computed of this compound by the B3LYP/6-31G(d) method are in a good agreement with the observed IR spectral data. Theoretical vibrational spectra of the title compound were interpreted by means of PEDs using VEDA 4 program.     

Vibrational spectra and assignments of 3-aminobenzyl alcohol by ab initio Hartree-Fock and density functional method

In this work, we will report a combined experimental and theoretical study on molecular and vibrational structure of 3-aminobenzyl alcohol. The FT-Raman and FT-IR spectra of 3-aminobenzyl alcohol were recorded in the solid phase. The equilibrium geometry, harmonic vibrational frequencies, infrared intensities, Raman scattering activities, depolarization ratios and reduced masses were calculated by ab initio HF and density functional B3LYP method with 6-311+G(d,p) basis sets. The scaled theoretical wavenumbers showed very good agreement with the experimental values. The thermodynamic functions of the title compound were also performed at HF/6-311+G(d,p) and B3LYP/6-311+G(d,p) levels of theory. A detailed interpretation of the infrared and Raman spectra of 3-aminobenzyl alcohol is reported. The theoretical spectrograms for FT-IR spectra of the title molecule have been constructed.     

Vibrational spectroscopy investigation using ab initio and density functional theory analysis on the structure of 5-amino-o-cresol

The Fourier transform Raman and Fourier transform infrared spectra of 5-amino-o-cresol (5AOC) were recorded in the solid phase. The equilibrium geometry, harmonic vibrational frequencies, infrared intensities and Raman scattering activities were calculated by HF and density functional B3LYP method with the 6-311G(d,p) basis set. The scaled theoretical wavenumbers showed very good agreement with the experimental values. The thermodynamic functions of the title compound were also performed at HF/6-311G(d,p) and B3LYP/6-311G(d,p) levels of theory. A detailed interpretation of the infrared and Raman spectra of 5-amino-o-cresol is reported. The theoretical spectrograms for FT-IR spectra of the title molecule have been constructed.     

FT-IR, FT-Raman spectra and ab initio HF and DFT calculations of 4-N,N'-dimethylamino pyridine

In this work, we will report a combined experimental and theoretical study on molecular and vibrational structure of 4-N,N'-dimethylamino pyridine (4NN'DMAP). The Fourier transform infrared and Fourier transform Raman spectra of 4NN'DMAP was recorded in the solid phase. The optimized geometry was calculated by HF and B3LYP methods with 6-31G(d,p) and 6-311++G(d,p) basis sets. The harmonic vibrational frequencies, infrared intensities and Raman scattering activities of the title compound were performed at same level of theories. The scaled theoretical wavenumber showed very good agreement with the experimental values. The thermodynamic functions of the title compound was also performed at HF/6-31G(d,p) and B3LYP/6-311++G(d,p) level of theories. A detailed interpretation of the infrared and Raman spectra of 4NN'DMAP was reported. The theoretical spectrograms for FT-IR and FT-Raman spectra of the title molecule have been constructed.     

FT-Raman and FT-IR spectra, ab initio and density functional studies of 2-amino-4,5-difluorobenzoic acid

The Fourier transform Raman and Fourier transform infrared spectra of 2-amino-4,5-difluorobenzoic acid (2A45DFBA) were recorded in the solid phase. The equilibrium geometry, harmonic vibrational frequencies, infrared intensities and Raman scattering activities, depolarization ratios were calculated by HF and density functional B3LYP method with the 6-31+G(d, p) and 6-311+G(d, p) basis sets. The scaled theoretical wavenumbers showed very good agreement with the experimental values. The thermodynamic functions of the title compound were also performed at HF/6-31+G(d, p)/6-311+G(d, p) and B3LYP/6-31+G(d, p)/6-311+G(d, p) levels of theory. A detailed interpretations of the infrared and Raman spectra of 2-amino-4,5-difluorobenzoic acid is reported. The theoretical spectrograms for FT-IR spectra of the title molecule have been constructed.     

Vibrational spectra and assignments using ab initio and density functional theory analysis on the structure of biotin

Density functional theory (DFT) and Hartree-Fock calculations were performed using the following models: HF/6-311G(d), B3LYP/6-311G(d), B3LYP/6-311+G(d) and B3PW91/6-311G(d) calculations were performed for biotin. It has been characterized by IR and X-ray. The calculated results show that the predicted geometry can well reproduce the structural parameters. Predicted vibrational frequencies have been assigned and compared with experimental IR spectra and they supported each other. On the basis of vibrational analyses, the thermodynamic properties of the title compound at different temperatures have been calculated, revealing the correlations between Cp,m degrees, Sm degrees, Hm degrees and temperatures.     

Molecular structure and vibrational spectra of phenobaraitone by density functional theory and ab initio hartree-Fock calculations

Quantum chemistry calculations have been performed using Gaussian03 program to compute optimized geometry, harmonic vibrational frequency along with intensities in IR and Raman spectra at RHF/6-31++G** and B3LYP/6-31++G** levels for phenobarbitone (C₁₂H₁₂N₂O₃) in the ground state. The scaled harmonic vibrational frequencies have been compared with experimental FT-IR and FT-Raman spectra. Theoretical vibrational spectra of the title compound were interpreted by means of potential energy distributions (PEDs) using MOLVIB program. A detailed interpretation of the infrared spectra of the title compound is reported. On the basis of the agreement between the calculated and observed results, the assignments of fundamental vibrational modes of phenobarbitone were examined and some assignments were proposed. The theoretical spectrograms for FT-IR and FT-Raman spectra of the title compound have been constructed.     

Molecular structure, vibrational, UV and NBO analysis of 4-chloro-7-nitrobenzofurazan by DFT calculations

In the present work, we reported a combined experimental and theoretical study on molecular structure, vibrational spectra and NBO analysis of 4-chloro-7-nitrobenzofurazan (NBD-Chloride). The FT-IR (400-4000 cm(-1)) and FT-Raman spectra (50-4000 cm(-1)) of NBD-Chloride were recorded. The molecular geometry, harmonic vibrational frequencies and bonding features of NBD-Chloride in the ground-state have been calculated by using the density functional B3LYP method with 6-311++G (d, p) as higher basis set. The energy and oscillator strength calculated by time-dependent density functional theory (TD-DFT) result in DMSO and CDCl3 solvents complements with each other. The calculated HOMO and LUMO energies show that charge transfer occurs within the molecule. Finally the calculation results were applied to simulate infrared and Raman spectra of the title compound which show good agreement with observed spectra.     

Vibrational spectroscopy investigation using ab initio and density functional theory analysis on the structure of 3-aminobenzotrifluoride

In this work, we will report a combined experimental and theoretical study on molecular and vibrational structure of 3-aminobenzotrifluoride. The FT-Raman and Fourier transform infrared spectra of 3-aminobenzotrifluoride (3ABTF) were recorded in the liquid phase. The equilibrium geometry, harmonic vibrational frequencies, infrared intensities and Raman scattering activities, depolarization ratios, reduced masses were calculated by HF and density functional B3LYP method with the 6-31G(d,p) and 6-311G(d,p) basis sets. The scaled theoretical wavenumbers showed very good agreement with the experimental values. The thermodynamic functions of the title compound were also performed at HF/6-31G(d,p)/6-311G(d,p) and B3LYP/6-31G(d,p)/6-311G(d,p) levels of theory. A detailed interpretations of the infrared and Raman spectra of 3ABTF is reported. The theoretical spectrograms for FT-IR spectra of the title molecule have been constructed.     

Vibrational spectra and fundamental structural assignments from HF and DFT calculations of methyl benzoate

The Fourier transform Raman and Fourier transform infrared spectra of methyl benzoate (MB) were recorded in the liquid phase. The equilibrium geometry, harmonic vibrational frequencies, infrared intensities and Raman scattering activities, depolarization ratios, reduced masses were calculated by Hartree-Fock (HF) and density functional B3LYP method with the 6-311+G(d,p) basis set. The scaled theoretical wavenumbers showed very good agreement with the experimental values. The thermodynamic functions of the title compound were also performed at HF/6-311+G(d,p) and B3LYP/6-311+G(d,p) levels of theory. A detailed interpretations of the infrared and Raman spectra of methyl benzoate is reported. The theoretical spectrograms for FT-IR spectra of the title molecule have been constructed.     

Vibrational assignment of the spectral data and thermodynamic properties of 2-chloro-4-fluorobenzophenone using DFT quantum chemical calculations

The FT-Raman (3500-100 cm⁻¹) and FT-IR (4000-450 cm⁻¹) spectra of 2-chloro-4-fluorobenzophenone were recorded in the solid phase. Density functional theory calculations with B3LYP/6-31G (d, p) basis set was used to determine the ground state molecular geometries (bond lengths and bond angles), harmonic vibrational frequencies, infrared intensities and Raman activities of this compound. Potential energy distributions (PEDs) and normal modes, for the spectral data computed at B3LYP/6-31G (d, p) level, have also been obtained from force-field calculations. The wavenumbers found after scaling of the force field showed very good agreement with the experimentally determined values. A comparison of the theoretical spectra and experimental FT-IR and FT-Raman spectra of the title molecule has been made and full vibrational assignments of the observed spectra have been proposed. On the basis of vibrational analyses, the thermodynamic properties of title compound at different temperatures have been calculated.     

Synthesis, IR spectra, crystal structure and DFT studies on 1-acetyl-3-(4-chlorophenyl)-5-(4-methylphenyl)-2-pyrazoline

1-Acetyl-3-(4-chlorophenyl)-5-(4-methylphenyl)-2-pyrazoline has been synthesized and characterized by elemental analysis, IR and X-ray single crystal diffraction. Density functional (DFT) calculations have been carried out for the title compound by using the B3LYP method at the 6-311G** basis set level. The calculated results show that the predicted geometry can reproduce well the structural parameters. Predicted vibrational frequencies have been assigned and compared with experimental IR spectra and they are supported each other. On the basis of vibrational analyses, the thermodynamic properties of the title compound at different temperatures have been calculated, revealing the correlations between C(0)(p, m), S(0)(m), H(0)(m) and temperatures.     

Molecular structure and vibrational analysis of 3-Ethylpyridine using ab initio HF and density functional theory (B3LYP) calculations

The FT-Raman and FT-IR spectra for 3-Ethylpyridine (3-EP) have been recorded in the region 4000-100 cm(-1) and compared with the harmonic vibrational frequencies calculated using HF/DFT (B3LYP) method by employing 6-31G(d,p) and 6-311++G(d,p) basis set with appropriate scale factors. IR intensities and Raman activities are also calculated by HF and DFT (B3LYP) methods. Optimized geometries of the molecule have been interpreted and compared with the reported experimental values of some substituted benzene. The experimental geometrical parameters show satisfactory agreement with the theoretical prediction from HF and DFT. The scaled vibrational frequencies at B3LYP/6-311++G(d,p) seem to coincide with the experimentally observed values with acceptable deviations. The theoretical spectrograms (IR and Raman) have been constructed and compared with the experimental FT-IR and FT-Raman spectra. Some of the vibrational frequencies of the pyridine are effected upon profusely with the C2H5 substitutions in comparison to pyridine and these differences are interpreted.     

Structural and vibrational investigation of para-nitraminopyridine N-oxide. A combined experimental and theoretical studies

The X-ray and vibrational spectroscopic analysis of para-nitraminopyridine N-oxide are reported. The crystals of investigated compound belong to P2(1) of the monoclinic system, Z=4, a=3.735 A, b=11.767 A, c=14.679 A and beta=93.27 degrees . Room temperature powder infrared and Raman spectra of the title compound and its deuterated analogue were measured. The molecular structure of p-nitraminopyridine N-oxide has been calculated with the aid of density functional (B3LYP) method with the extended 6-311++G(d,p) basis set. The calculated geometrical parameters of investigated molecule in gas phase were compared with experimental X-ray data. The harmonic frequencies, potential energy distribution (PED) and IR intensities of p-nitroaminopyridine N-oxide and its deuterated analogue were calculated with B3LYP method. The assignment of the experimental spectra has been made on the basis of the calculated PED. The time depend Hartree-Fock (TDHF) method was used for calculations of hyperpolarizability beta coefficient.