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Puducherry, India

Nagabalasubramanian P.B.,University | Karabacak M.,Afyon Kocatepe University | Periandy S.,Tagore Arts College
Journal of Molecular Structure | Year: 2012

The FT-IR and FT-Raman spectra of nicotinic acid ethyl ester (abbreviated as NAEE, C8H9NO2) have been recorded in the region 3600-10 cm-1. Potential energy curve was computed by means of scanning CCCO torsion angle. The optimized geometric parameters geometry optimization and the energies associated possible two conformers (C1 and C2) were computed. The computational results diagnose the most stable conformer of NAEE as the C1 form. The optimum molecular geometries, energies, normal mode wavenumbers, infrared and Raman intensities, corresponding vibrational assignments, atomic charges, HOMO-LUMO analysis and thermo-dynamical parameters were investigated with the help of HF, B3LYP and LSDA methods with 6-311G(d,p) and 6-311G++(d,p) basis sets. Reliable vibrational assignments were made on the basis of total energy distribution (TED) calculated with scaled quantum mechanics (SQM) method. Thermodynamic properties of the title compound at different temperatures were calculated. The results of the calculations were applied to simulate infrared and Raman spectra of the title compound which show excellent agreement with the observed spectra. © 2012 Elsevier B.V. All rights reserved. Source


Govindarajan M.,MGGA College | Periandy S.,Tagore Arts College | Carthigayen K.,Bharathiyar University | Carthigayen K.,Dr Br Ambedkar Polytechnic College
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2012

In this work, the vibrational spectral analysis was carried out by using Raman and infrared spectroscopy in the range 100-4000 cm-1 and 50-4000 cm-1, respectively, for the title molecules. The molecular structure, fundamental vibrational frequencies and intensity of the vibrational bands are interpreted with the aid of structure optimizations and normal coordinate force field calculations based on Hartee Fock (HF) and density functional theory (DFT) method and different basis sets combination. The complete vibrational assignments of wavenumbers were made on the basis of potential energy distribution (PED). The scaled B3LYP/6-311++G(d,p) results show the best agreement with the experimental values over the other methods. The calculated HOMO and LUMO energies show that charge transfer occurs within molecule. The influences of bromine atom and methyl group on the geometry of benzene and its normal modes of vibrations have also been discussed. The results of the calculations were applied to simulated spectra of the title compounds, which show excellent agreement with observed spectra. © 2012 Elsevier B.V. All rights reserved. Source


Nagabalasubramanian P.B.,University | Karabacak M.,Afyon Kocatepe University | Periandy S.,Tagore Arts College
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2012

In this work, the FT-IR and FT-Raman spectrum of 1-(chloromethyl)-2-methyl naphthalene (abbreviated as 1-ClM-2MN, C 12H 11Cl) have been recorded in the region 3600-10 cm -1. The optimum molecular geometry, normal mode wavenumbers, infrared and Raman intensities, Raman scattering activities, corresponding vibrational assignments, Mullikan atomic charges and thermo-dynamical parameters were investigated with the help of HF and B3LYP (DFT) method using 6-311G(d,p), 6-311++G(d,p) basis sets. Also, the dipole moment, linear polarizabilities, anisotropy, first and second hyperpolarizabilities values were also computed using the same basis set. Reliable vibrational assignments were made on the basis of total energy distribution (TED) calculated with scaled quantum mechanical (SQM) method. The correlation equations between heat capacities, entropies, enthalpy changes and temperatures were fitted by quadratic formulas. Lower value in the HOMO and LUMO energy gap explains the eventual charge transfer interactions taking place within the molecule. UV-vis spectral analysis of 1-ClM-2MN has been researched by theoretical calculations. In order to understand the electronic transitions of the compound, TD-DFT calculations on electronic absorption spectra in gas phase and solvent (DMSO and chloroform) were performed. The calculated frontier orbital energies, absorption wavelengths (λ), oscillator strengths (f) and excitation energies (E) for gas phase and solvent are also illustrated. © 2011 Elsevier B.V. All rights reserved. Source


Govindarajan M.,MGGA College | Karabacak M.,Afyon Kocatepe University | Udayakumar V.,Thiru A Govindaswamy Arts College | Periandy S.,Tagore Arts College
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2012

In this work, the vibrational spectral analysis was carried out by using FT-Raman and FT-IR spectroscopy in the range 100-4000 cm -1 and 400-4000 cm -1 respectively, for the title molecule. The molecular structure, fundamental vibrational frequencies and intensity of the vibrational bands are interpreted with the aid of structure optimizations and normal coordinate force field calculations based on Hartree Fock (HF) and density functional theory (DFT) method and different basis sets combination. The complete vibrational assignments of wavenumbers were made on the basis of potential energy distribution (PED). The scaled B3LYP/6-311++G(d,p) results show the best agreement with the experimental values over the other methods. The effects due to the substitution of halogen bond were investigated. The results of the calculations were applied to simulated spectra of the title compound, which show excellent agreement with observed spectra. The energy and oscillator strength calculated by Time-Dependent Density Functional Theory (TD-DFT) results complements with the experimental findings. Besides, frontier molecular orbitals (FMO), molecular electrostatic potential (MEP), and thermodynamic properties were performed. The thermodynamic properties of the title compound at different temperatures have been calculated, revealing the correlations between heat capacity (C), entropy (S), and enthalpy changes (H) and temperatures. © 2011 Elsevier B.V. All rights reserved. Source


Govindarajan M.,MGGA College | Karabacak M.,Afyon Kocatepe University | Suvitha A.,Periyar University | Periandy S.,Tagore Arts College
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2012

In this work, the vibrational spectral analysis was carried out by using Raman and infrared spectroscopy in the range 100-4000 cm -1 and 50-4000 cm -1, respectively, for 4-chloro-3-nitrotoluene (C 7H 6NO 2Cl) molecule. The molecular structure, fundamental vibrational frequencies and intensity of the vibrational bands are interpreted with the aid of structure optimizations and normal coordinate force field calculations based on Hartree Fock (HF) and density functional theory (DFT) method and different basis sets combination. The complete vibrational assignments of wavenumbers were made on the basis of potential energy distribution (PED). The scaled B3LYP/6-311++G(d,p) results show the best agreement with the experimental values over the other methods. The calculated HOMO and LUMO energies shows that charge transfer within the molecule. The effects due to the substitutions of methyl group, nitro group and halogen were investigated. The results of the calculations were applied to simulate spectra of the title compound, which show excellent agreement with observed spectra. Besides, frontier molecular orbitals (FMO), molecular electrostatic potential (MEP) and thermodynamic properties were performed. © 2011 Elsevier B.V. Source

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