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Tiruchirappalli, India

Arivazhagan M.,Aa Government Arts College | Meenakshi R.,Cauvery College for Women | Prabhakaran S.,Jamal Mohamed College Autonomous
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2013

Quantum chemical density functional calculations were carried out for PFBN with the GAUSSIAN 09W using ab initio and Becke-3-Lee-Yang-Parr (B3LYP) functional. The observed FT-IR and FT-Raman vibrational frequencies are analyzed and compared with theoretically predicted vibrational frequencies. The geometries and normal modes of vibration obtained from DFT method are in good agreement with the experimental data. The first-order hyperpolarizability (β) of the investigated molecule was computed using DFT calculations. The calculated HOMO and LUMO energies shows that charge transfer occur within molecule. The influences of nitrogen on the geometry of benzene and its normal modes of vibrations have also been discussed. The UV-Vis spectral analysis of PFBN has also been done which confirms the charge transfer of PFBN. The chemical shifts of H atoms and C atoms were calculated using NMR analysis. © 2012 Elsevier B.V. All rights reserved. Source


Arivazhagan M.,Aa Government Arts College | Anitha Rexalin D.,Cauvery College for Women
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2013

The FT-IR and FT-Raman vibrational spectra of ninhydrin have been recorded in the range 4000-400 cm-1and 3600-50 cm-1, respectively. A detailed vibrational spectral analysis has been carried out and assignments of the observed fundamental bands have been proposed on the basis of peak positions and relative intensities. The optimized molecular geometry, vibrational frequencies, atomic charges, dipole moment, rotational constants and several thermodynamic parameters in the ground state are calculated using ab initio HF and density functional B3LYP methods with 6-311++G(d,p) basis set combination. In order to find the most optimized geometry, the energy calculations are carried out for various possible conformers. Keto and enol forms of ninhydrin are also studied. The condensed summary of the principal NBOs shows the occupancy, orbital energy and the qualitative pattern of delocalization interactions of ninhydrin. The calculated HOMO-LUMO energies reveal that charge transfer occurs within the molecule. The predicted first hyperpolarizability also shows that the ninhydrin molecule have good optical quality and nonlinear optical (NLO) behavior. With the help of specific scaling procedures, the observed vibrational wave numbers in FT-IR and FT-Raman spectra are analyzed and assigned to different normal modes of the molecule. © 2012 Elsevier B.V. All rights reserved. Source


Arivazhagan M.,Aa Government Arts College | Anitha Rexalin D.,Cauvery College for Women
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2012

The Fourier transform infrared (FT-IR) and Fourier transform Raman (FT-Raman) spectra of 4-chloro-2-fluoroaniline (CFA) have been recorded and analyzed. The equilibrium geometry, bonding features and harmonic vibrational frequencies have been investigated with the help of ab initio and density functional theory (DFT) methods. 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. The 1H and 13C nuclear magnetic resonance (NMR) chemical shifts of the molecule are 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 CFA are calculated using B3LYP/6-311++G(d,p) and HF/6-311++G(d,p) methods on the finite-field approach. The calculated results also show that the CFA molecule might have microscopic nonlinear optical (NLO) behavior with non-zero values. Stability of the molecule arising from hyper conjugative interactions, charge delocalization has been analyzed using natural bond orbital (NBO) analysis. The result confirms the occurrence of intramolecular charge transfer (ICT) within the molecule. The HOMO-LUMO energies UV-vis spectral analysis and MEP are performed by B3LYP/6-311++G(d,p) approach. A detailed interpretation of the infrared and Raman spectra of CFA is also reported based on total energy distribution (TED). The difference between the observed and scaled wave number values of the most of the fundamentals is very small. © 2012 Elsevier B.V. All rights reserved. Source


Arivazhagan M.,Aa Government Arts College | Anitha Rexalin D.,Cauvery College for Women
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2011

In this work, the experimental and theoretical vibrational spectra of 1-bromonaphthalene (1-BN) were studied. FTIR and FT Raman spectra were recorded in the region 4000-400 cm -1 and 3500-50 cm -1, respectively. The structural and spectroscopic data of the molecule in the ground state were calculated by using ab initio Hartree-Fock and density functional method (B3LYP) with the 6-311++G(d,p) basis set. The vibrational frequencies were calculated and scaled values were compared with experimental FTIR and FT Raman spectra. The observed and calculated frequencies are found to be in good agreement. The complete assignments were performed on the basis of the total energy distribution (TED) of the vibrational modes, calculated with scaled quantum mechanics (SQM) method. The optimized geometric parameters were calculated. The predicted first hyperpolarizability also shows that the molecule might have a reasonably good nonlinear optical (NLO) behaviour. The calculated HOMO-LUMO energy gap reveals that charge transfer occurs within the molecule. © 2011 Elsevier B.V. Source


Gayathri R.,Cauvery College for Women | Arivazhagan M.,Aa Government Arts College
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2011

Vibrational spectral measurements, namely, FT-infrared (4000-400 cm -1) and FT-Raman (3500-50 cm -1) spectra have been made for 1,3-dichloro 5-nitrobenzene (DCNB) and assigned to different normal modes of the molecule. Optimized geometrical structure, harmonic vibrational frequencies, intensities, Mulliken's net charges and several thermodynamic parameters in the ground state have been computed by the B3LYP, density functional method using 6-311+G(d,p),6-311++G(d,p) basis sets. Complete assignments of the observed spectra have been proposed. Most of the modes have wave numbers in the expected range. Coupling of vibrations has been determined by calculating total energy distributions (TED) with the help of specific scaling procedures. The calculated HOMO and LUMO energies and electrostatic potential shows that charge transfer occurs within the molecule. The results of the calculations were applied to simulated infrared and Raman spectra of the title compound which showed excellent agreement with the observed spectra. © 2011 Elsevier B.V. All Rights Reserved. Source

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