Time filter

Source Type

Gnanasambandan T.,SCSVMV University | Gunasekaran S.,Spectrophysics Research Laboratory | Seshadri S.,Ln Government Arts College
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2013

A combined experimental and theoretical study on molecular structure, vibrational spectra, NBO and UV-spectral analysis of m-nitromethylbenzoate (MNMB) has been reported in the present work. The FT-IR solid phase (4000-400 cm1) and FT-Raman spectra (3500-100 cm1) of MNMB was recorded. The molecular geometry, harmonic vibrational frequencies and bonding features of MNMB in the ground-state have been calculated by using the density functional method B3LYP with 6-31G (d,p) and 6-31+G(d,p) basis sets. The assignments of the vibrational spectra have been carried out with the help of normal co-ordinate analysis (NCA) following the Scaled Quantum Mechanical Force Field Methodology (SQMFF). Stability of the molecule arising from hyperconjugative interactions, charge delocalization has been analyzed using natural bond orbital (NBO) analysis. The results show that charge in electron density (ED) in the ct-antibonding orbitals and E(2) energies confirms the occurrence of ICT (Intra-molecular Charge Transfer) within the molecule. The UV spectrum was measured in ethyl acetate solution. The energy and oscillator strength calculated by Time-Dependent Density Functional Theory (TD-DFT) result complements the experimental findings. The calculated HOMO and LUMO energies show that charge transfer occurs within the molecule. Finally the calculation results were applied to simulated infrared and Raman spectra of the title compound which show good agreement with observed spectra. © 2013 Elsevier B.V. All rights reserved.


Gnanasambandan T.,SCSVMV University | Gunasekaran S.,St Peters University | Seshadri S.,Ln Government Arts College
Journal of Molecular Structure | Year: 2014

The FT-IR (4000-400 cm-1) and FT-Raman spectra (3500-100 cm -1) of chlorzoxazone (CHLZ) have been recorded in the condensed state. Density functional theory calculation with B3LYP/6-31G(d,p) basis set have been used to determine ground state molecular geometries (bond length and bond angle), harmonic vibrational frequencies, infrared intensities, Raman activities and bonding features of the title compound. The assignments of the vibrational spectra have been carried out with the help of normal co-ordinate analysis (NCA) following the scaled quantum mechanical force field (SQMFF) methodology. The first order hyperpolarizability (β0) and related properties (β, α0 and Δα) of CHLZ is calculated using B3LYP/6-31G(d,p) method on the finite-field approach. The stability of molecule has been analyzed by using NBO analysis. The calculated HOMO and LUMO energies show that charge transfer occurs within these molecules. Mulliken population analysis on atomic charges is also calculated. Because of vibrational analyses, the thermodynamic properties of the title compound at different temperatures have been calculated. Finally, the UV-Vis spectra and electronic absorption properties were explained and illustrated from the frontier molecular orbitals. © 2014 Elsevier B.V. All rights reserved.


Gnanasambandan T.,SCSVMV University | Gunasekaran S.,Spectrophysics Research Laboratory | Seshadri S.,Ln Government Arts College
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2014

The spectroscopic properties of the p-nitroacetanilide (PNA) were examined by FT-IR, FT-Raman and UV-Vis techniques. FT-IR and FT-Raman spectra in solid state were observed in the region 4000-400 cm-1 and 3500-100 cm -1, respectively. The UV-Vis absorption spectrum of the compound that dissolved in ethanol was recorded in the range of 200-400 nm. The structural and spectroscopic data of the molecule in the ground state were calculated by using density functional theory (DFT) employing B3LYP methods with the 6-31G(d,p) and 6-311+G(d,p) basis sets. The geometry of the molecule was fully optimized, vibrational spectra were calculated and fundamental vibrations were assigned on the basis of the total energy distribution (TED) of the vibrational modes, calculated with scaled quantum mechanics (SQM) method. Thermodynamic properties like entropy, heat capacity and enthalpy have been calculated for the molecule. HOMO-LUMO energy gap has been calculated. The intramolecular contacts have been interpreted using natural bond orbital (NBO) and natural localized molecular orbital (NLMO) analysis. Important non-linear optical (NLO) properties such as electric dipole moment and first hyperpolarizability have been computed using B3LYP quantum chemical calculation. © 2013 Elsevier B.V. All rights reserved.


Rajesh P.,Pachaiyappas College | Gunasekaran S.,St Peters University | Seshadri S.,Ln Government Arts College
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2014

The complete vibrational assignment and analysis of the fundamental vibrational modes of Trifluoperazine (TFZ) was carried out using the experimental FT-IR, FT-Raman and UV-Vis data and quantum chemical studies. The observed vibrational data were compared with the wavenumbers derived theoretically for the optimized geometry of the compound from the DFT-B3LYP gradient calculations employing 6-31G (d,p) basis set. Thermodynamic properties like entropy, heat capacity and enthalpy have been calculated for the molecule. The HOMO-LUMO energy gap has been calculated. The intramolecular contacts have been interpreted using natural bond orbital (NBO) and natural localized molecular orbital (NLMO) analysis. Important non-linear properties such as first hyperpolarizability of TFZ have been computed using B3LYP quantum chemical calculation. © 2014 Elsevier B.V. All rights reserved.


Gnanasambandan T.,SCSVMV University | Gunasekaran S.,Spectrophysics Research Laboratory | Seshadri S.,Ln Government Arts College
Oriental Journal of Chemistry | Year: 2013

The FT-IR and FT-Raman vibrational spectra of selegiline were recorded. The optimized geometry and wavenumbers in the ground state were calculated using density functional (B3LYP) method with standard 6-31G(d,p) basis set. The computed B3LYP/6-31G(d,p) results show the best agreement with the experimental values over the other methods. Natural bond orbital analysis of selegiline is also carried out, which confirms the occurrence of strong intermolecular bonding, stability of the molecule arising from hyperconjugative interactions, and charge delocalization. The electric dipole moment (α), polarizability (α), and first hyperpolarizability (β0) which results also show that the selegiline might have microscopic non-linear optical behavior with non-zero values. The calculated HOMO and LUMO energies show that charge transfer occur in the molecule. The results of the calculations were applied to simulated spectra of the title compound, which show excellent agreement with observed spectra.


Gnanasambandan T.,SCSVMV University | Gunasekaran S.,St Peter University | Seshadri S.,Ln Government Arts College
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2014

This work presents the characterization of p-bromoacetanilide (PBA) by quantum chemical calculations and spectral techniques. The spectroscopic properties were investigated by FT-IR, FT-Raman and UV-Vis techniques. The structural and spectroscopic data of the molecule were obtained from B3LYP/6-311++ G(d,p) and MPW1PW91/6-311++G(d,p) basis set calculations. The theoretical wavenumbers were scaled and compared with experimental FT-IR and FT-Raman spectra. The complete assignments were performed on the basis of the normal co-ordinate analysis (NCA), experimental results and potential energy distribution (PED) of the vibrational modes, calculated with scaled quantum mechanics (SQM) method, interpreted in terms of fundamental modes. The stability of molecule has been analyzed by NBO/NLMO analysis. The molecular orbital contributions were studied by using the density of states. The electronic properties like UV-Vis spectral analysis and HOMO-LUMO energies were reported. The calculated HOMO and LUMO energies shows that charge transfer interactions taking place within the molecule. Mulliken population analysis on atomic charges, Statistical thermodynamic properties at various temperatures of the PBA is also calculated. © 2013 Elsevier B.V. All rights reserved.


PubMed | St Peters University, Meenakshi Academy of Higher Education & Research and Ln Government Arts College
Type: | Journal: Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy | Year: 2015

The Fourier transform infrared (FT-IR) and the Fourier transform Raman (FT-Raman) spectra of the title molecule in solid phase were recorded in the region 4000-400 cm(-1) and 4000-100 cm(-1) respectively. The geometrical parameters and energies were investigated with the help of Density Functional Theory (DFT) employing B3LYP method and 6-31G (d, p) basis set. The analysis was supported by electrostatic potential maps and calculation of HOMO-LUMO. UV, FT-IR and FT-Raman spectra of ornidazole were calculated and compared with experimental results. Thermodynamic properties like entropy, heat capacity, have been calculated for the molecule. The predicted first hyperpolarizability also shows that the molecule might have a reasonably good non-linear optical (NLO) behavior. The intramolecular contacts have been interpreted using natural bond orbital (NBO) and natural localized molecular orbital (NLMO) analysis.


Saravanan R.R.,AMET University | Seshadri S.,Ln Government Arts College | Gunasekaran S.,St Peters University | Mendoza-Merono R.,University of Oviedo | Garcia-Granda S.,University of Oviedo
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2014

Crystallographic, experimental (FT-IR and FT-RS) and theoretical density function theory (DFT) and UV-Vis spectra of (E)-1-[1-(4-Chlorophenyl)ethylidene] thiosemicarbazide) (ECET) are investigated. The optimized geometry of the compound was calculated from the DFT-B3LYP gradient calculations employing 6-31G (d,p) basis set and calculated vibrational frequencies are evaluated via comparison with experimental values. Molecular stability has been analyzed using Natural Bond Orbital (NBO) and Natural Localized Molecular Orbital (NLMO) analysis and the limits of the molecular electrostatic potential observed. The calculated HOMO and LUMO energies show the charge transfer occurs within the molecule.© 2013 Elsevier B.V. All rights reserved.


PubMed | AMET University, Ln Government Arts College, St Peters University and University of Oviedo
Type: | Journal: Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy | Year: 2014

Crystallographic, experimental (FT-IR and FT-RS) and theoretical density function theory (DFT) and UV-Vis spectra of (E)-1-[1-(4-Chlorophenyl)ethylidene]thiosemicarbazide) (ECET) are investigated. The optimized geometry of the compound was calculated from the DFT-B3LYP gradient calculations employing 6-31G (d,p) basis set and calculated vibrational frequencies are evaluated via comparison with experimental values. Molecular stability has been analyzed using Natural Bond Orbital (NBO) and Natural Localized Molecular Orbital (NLMO) analysis and the limits of the molecular electrostatic potential observed. The calculated HOMO and LUMO energies show the charge transfer occurs within the molecule.


PubMed | Ln Government Arts College, SCSVMV University and St Peter University
Type: | Journal: Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy | Year: 2014

This work presents the characterization of p-bromoacetanilide (PBA) by quantum chemical calculations and spectral techniques. The spectroscopic properties were investigated by FT-IR, FT-Raman and UV-Vis techniques. The structural and spectroscopic data of the molecule were obtained from B3LYP/6-311++ G(d,p) and MPW1PW91/6-311++G(d,p) basis set calculations. The theoretical wavenumbers were scaled and compared with experimental FT-IR and FT-Raman spectra. The complete assignments were performed on the basis of the normal co-ordinate analysis (NCA), experimental results and potential energy distribution (PED) of the vibrational modes, calculated with scaled quantum mechanics (SQM) method, interpreted in terms of fundamental modes. The stability of molecule has been analyzed by NBO/NLMO analysis. The molecular orbital contributions were studied by using the density of states. The electronic properties like UV-Vis spectral analysis and HOMO-LUMO energies were reported. The calculated HOMO and LUMO energies shows that charge transfer interactions taking place within the molecule. Mulliken population analysis on atomic charges, Statistical thermodynamic properties at various temperatures of the PBA is also calculated.

Loading Ln Government Arts College collaborators
Loading Ln Government Arts College collaborators