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PubMed | Government College of Technology, Coimbatore, Annamalai University, DMI-St. EUGENE University and Sri Manakula Vinayagar Engg College
Type: | Journal: Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy | Year: 2014

In this work we analyzed the vibrational spectra of 3,5-dinitrosalicylic acid (3,5DNSA) molecule. The total energy of eight possible conformers can be calculated by Density Functional Theory with 6-31G(d,p) as basis set to find the most stable conformer. Computational result identify the most stable conformer of 3,5DNSA is C6. The assignments of the vibrational spectra have been carried out by computing Total Energy Distribution (TED). The molecular geometry, second order perturbation energies and Electron Density (ED) transfer from filled lone pairs of Lewis base to unfilled Lewis acid sites for 3,5-DNSA molecular analyzed on the basis of Natural Bond Orbital (NBO) analysis. The formation of inter and intramolecular hydrogen bonding between OH and COOH group gave the evidence for the formation of dimer formation for 3,5-DNSA molecule. The energy and oscillator strength calculated by Time-Dependent Density Functional Theory (TD-DFT) complements with the experimental findings. The simulated spectra satisfactorily coincides with the experimental spectra.


PubMed | Government College of Technology, Coimbatore, Annai Velankanni College, Government of Puducherry, DMI-St. EUGENE University and Sri Manakula Vinayagar Engg College
Type: | Journal: Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy | Year: 2014

In this work we report the vibrational spectral analysis of l-Asparagine Monohydrate (LAM) molecule by using FT-IR and FT-Raman spectroscopic techniques. The equilibrium geometry, harmonic vibrational wavenumbers, various bonding features have been computed using density functional B3LYP method with 6-311G(d,p) as basis set. Stability of the molecule arising from hyperconjugative interactions, charge delocalization have been analyzed using natural bond orbital (NBO) analysis. The results show that charge in electron density (ED) in (*) and (*) antibonding orbitals and second order delocalization energies E((2)) confirms the occurrence of Intramolecular Charge Transfer (ICT) within the molecule. The energy and oscillator strength calculated by Time-Dependent Density Functional Theory (TD-DFT) complements with the experimental findings. The simulated spectra satisfactorily coincide with the experimental spectra.


Amalanathan M.,Annai Velankanni College | Sebastian S.,Sri Manakula Vinayagar Engg College | Sajan D.,Bishop Moore College | Hubert Joe I.,Center for Molecular and Biophysics Research | And 2 more authors.
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2013

The molecular geometry, the normal mode frequencies and corresponding vibrational assignments, natural bond orbital analysis and the HOMO-LUMO analysis of 7-Amino-2,4-dimethylquinolinium formate in the ground state were performed by B3LYP levels of theory using the 6-31G(d) basis set. The optimised bond lengths and bond angles are in good agreement with the X-ray data. The vibrational spectra of the title compound which is calculated by DFT method, reproduces vibrational wave numbers and intensities with an accuracy which allows reliable vibrational assignments. The possibility of N- H···O hydrogen bonding was identified using NBO analysis. Natural bond orbital analysis confirms the presence of intramolecular charge transfer and the hydrogen bonding interaction. © 2013 The Authors.


Sebastian S.,Sri Manakula Vinayagar Engg College | Sylvestre S.,Achariya Arts and Science College | Jayarajan D.,Divine Mother College | Amalanathan M.,Annai Velankanni College | And 3 more authors.
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2013

In this work, we report harmonic vibrational frequencies, molecular structure, NBO and HOMO, LUMO analysis of Umbelliferone also known as 7-hydroxycoumarin (7HC). The optimized geometric bond lengths and bond angles obtained by computation (monomer and dimmer) shows good agreement with experimental XRD data. Harmonic frequencies of 7HC were determined and analyzed by DFT utilizing 6-311+G(d,p) as basis set. The assignments of the vibrational spectra have been carried out with the help of Normal Coordinate Analysis (NCA) following the Scaled Quantum Mechanical Force Field Methodology (SQMFF). The change in electron density (ED) in the σ* and π* antibonding orbitals and stabilization energies E(2) have been calculated by Natural Bond Orbital (NBO) analysis to give clear evidence of stabilization originating in the hyperconjugation of hydrogen-bonded interaction. The energy and oscillator strength calculated by Time-Dependent Density Functional Theory (TD-DFT) complements with the experimental findings. The simulated spectra satisfactorily coincides with the experimental spectra. Microbial activity of studied compounds was tested against Staphylococcus aureus, Streptococcus pyogenes, Bacillus subtilis, Escherichia coli, Psuedomonas aeruginosa, Klebsiella pneumoniae, Proteus mirabilis, Shigella flexneri, Salmonella typhi and Enterococcus faecalis. © 2012 Published by Elsevier B.V. All rights reserved.


Sebastian S.,Sri Manakula Vinayagar Engg College | Sylvestre S.,Achariya Arts and Science College | Sundaraganesan N.,Annamalai University | Amalanathan M.,Annai Velankanni College | And 3 more authors.
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2013

Vibrational spectral analysis of 4-amino-3-hydroxy-1- naphthalenesulfonicacid (4A3HNSA) molecule were carried out using FT-IR and FT-Raman spectroscopic techniques. The equilibrium geometry, harmonic vibrational wavenumbers, various bonding features have been computed using density functional B3LYP method with 6-31G(d,p) as basis set. The Non-Linear Optical (NLO) behavior of 4A3HNSA has been studied by determination of the electric dipole moment (μ) and hyperpolarizability β using HF/6-31G(d,p) method. Stability of the molecule arising from hyperconjugative interactions, charge delocalization have been analyzed using natural bond orbital (NBO) analysis. The results show that charge in electron density (ED) in σ and π antibonding orbitals and second order delocalization energies (E2) confirms the occurrence of Intramolecular Charge Transfer (ICT) within the molecule. The energy and oscillator strength calculated by Time-Dependent Density Functional Theory (TD-DFT) complements with the experimental findings. The simulated spectra satisfactorily coincide with the experimental spectra. © 2013 Elsevier B.V. All rights reserved.


Sebastian S.,Sri Manakula Vinayagar Engg College | Sylvestre S.,Achariya Arts and Science College | Oudayakumar K.,Sri Manakula Vinayagar Engg College | Jayavarthanan T.,Sri Manakula Vinayagar Engg College | And 2 more authors.
Molecular Simulation | Year: 2013

Vibrational analysis of 2-amino-6-nitrobenzothiazole (2A6NBT) molecule has been carried out at room temperature using FT-IR and FT-Raman spectroscopic techniques. The equilibrium geometry, bonding features and harmonic vibrational frequencies have been investigated with the help of the density functional theory DFT method. The non-linear optical (NLO) behaviour of the examined molecule has been studied followed by the determination of the electric dipole moment , the polarisability α and hyperpolarisability β using HF/6-31G(d,p) method. Stability of the molecule arising from hyperconjugative interactions and charge delocalisation have been analysed using the natural bond orbital analysis. The results show that charge in electron density in the σ* and π* antibonding orbitals and second-order delocalisation energies (E2) confirms the occurrence of intramolecular charge transfer within the molecule. The assignments of the vibrational spectra have been carried out with the help of normal coordinate analysis following the scaled quantum mechanical force field methodology. The energy and oscillator strength calculated by time-dependent density functional theory complements with the experimental findings. The simulated spectra satisfactorily coincide with the experimental spectra. © 2013 Taylor and Francis.


Sylvestre S.,Achariya Arts and Science College | Sebastian S.,Sri Manakula Vinayagar Engg College | Oudayakumar K.,Sri Manakula Vinayagar Engg College | Jayavarthanan T.,Sri Manakula Vinayagar Engg College | Sundaraganesan N.,Annamalai University
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2012

Vibrational analysis of the planar electron-rich heterocyclic 2,3-diaminophenazine (DAP) molecule was carried out using FT-IR and FT-Raman spectroscopic techniques. The equilibrium geometry, harmonic vibrational wavenumbers, various bonding features have been computed using density functional method. The calculated molecular geometry parameters have been compared with XRD data. The detailed interpretation of the vibrational spectra has been carried out. The first order hyperpolarizability (β0) of the molecular system and related properties (β, α0 and Δα) of DAP are calculated using HF/6-31G(d,p) method on the basis of finite-field approach. Vibrational analysis reveals that the simultaneous IR and Raman activation of the C-C stretching mode in the molecule provide the evidence for the charge transfer interaction takes place from electron donating group to the ring. The energy and oscillator strength calculated by time-dependent density functional theory (TD-DFT) results complements with the experimental findings. The simulated spectra satisfactorily coincide with the experimental spectra. © 2012 Elsevier B.V. All rights reserved.


Krishnan A.R.,Annamalai University | Saleem H.,Annamalai University | Subashchandrabose S.,Annamalai University | Sundaraganesan N.,Annamalai University | Sebastain S.,Sri Manakula Vinayagar Engg College
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2011

In this work, we will report a combined experimental and theoretical study on molecular structure, vibrational spectra, NBO and UV spectral analysis of 2-chlorobenzonitrile (2-ClBN). The FT-IR solid phase (4000-400 cm-1), and FT-Raman spectra (3500-50 cm-1) of 2-ClBN was recorded. The molecular geometry, harmonic vibrational frequencies and bonding features of 2-ClBN in the ground state have been calculated by using the density functional methods (BLYP, B3LYP) with 6-31G(d,p) as basis set. 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 hyper conjugative interactions, charge delocalization has been analyzed using natural bond orbital (NBO) analysis. The results show that charge in electron density (ED) in the σ* and π* anti bonding orbitals and E2 energies confirms the occurrence of ICT (Intra molecular Charge Transfer) within the molecule. The UV spectrum was measured in ethanol solution. The energy and oscillator strength calculated by Time-Dependent Density Functional Theory (TD-DFT) results complements with the experimental findings. The calculated HOMO and LUMO energies also confirm that charge transfer occurs within the molecule. Finally calculated results were applied to simulated Infrared and Raman spectra of the title compound which show good agreement with observed spectra. © 2010 Elsevier B.V. All rights reserved.


Sebastian S.,Sri Manakula Vinayagar Engg College | Sundaraganesan N.,Annamalai University | Karthikeiyan B.,Annamalai University | Srinivasan V.,Annamalai University
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2011

The Fourier transform infrared (FT-IR) and FT-Raman of 4-methyl-2- cyanobiphenyl (4M2CBP) have been recorded and analyzed. The equilibrium geometry, bonding features and harmonic vibrational frequencies have been investigated with the help of density functional theory (DFT) method. The assignments of the vibrational spectra have been carried out with the help of normal coordinate analysis (NCA) following the scaled quantum mechanical force field methodology (SQMFF). The 1H and 13C nuclear magnetic resonance (NMR) chemical shifts of the molecule were calculated by the Gauge including atomic orbital (GIAO) method. The first order hyperpolarizability (β0) of this novel molecular system and related properties (β, α0 and Δα) of 4M2CBP are calculated using HF/6-311G(d,p) method on the finite-field approach. Stability of the molecule arising from hyperconjugative interactions, charge delocalization have been analyzed using natural bond orbital (NBO) analysis. The results show that charge in electron density (ED) in the σ* and π* antibonding orbitals and second order delocalization energies (E2) confirms the occurrence of intramolecular charge transfer (ICT) within the molecule. UV-vis spectrum of the compound was recorded and the electronic properties, such as HOMO and LUMO energies, were performed by time-dependent density functional theory (TD-DFT) approach. Finally the calculations results were applied to simulated infrared and Raman spectra of the title compound which show good agreement with observed spectra. © 2010 Elsevier B.V. All rights reserved.


Chandra S.,Annamalai University | Saleem H.,Annamalai University | Sebastian S.,Sri Manakula Vinayagar Engg College | Sundaraganesan N.,Annamalai University
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2011

In this work, we report a combined experimental and theoretical study on molecular structure (monomer, dimer), vibrational spectra, and Natural Bond Orbital (NBO) analysis of non-ionized l-cysteine (LCY). The FT-IR solid phase (4000-400 cm-1) and FT-Raman spectra (3500-50 cm-1) of LCY was recorded at room temperature. The molecular geometry, harmonic and anharmonic vibrational frequencies and bonding features of LCY in the ground state have been calculated by using the density functional method (B3LYP) with 6-311G(d,p) as basis set. 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) of this novel molecular system and related properties (β, α0 and Δα) of LCY are calculated using HF/6-311G(d,p) method on the finite-field approach. Stability of the molecule has been analyzed using NBO analysis. The calculated first hyperpolarizability shows that the molecule is an attractive molecule for future applications in non-linear optics. The calculated HOMO and LUMO energies show that charge transfer occurs within the molecule. Finally the calculations results were applied to stimulate infrared and Raman spectra of the title compound which show good agreement with observed spectra. © 2011 Elsevier B.V. All rights reserved.

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