Aa Government Arts College

Musiri, India

Aa Government Arts College

Musiri, India

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Balachandran V.,AA Government Arts College
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2013

In this work, the vibrational spectral analysis was carried out by FT-IR and FT-Raman spectroscopy in the regions of 4000-400 cm-1 and 3500-100 cm-1, respectively for 2′,4′- difluoroacetophenone (DFAP). 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), density functional theory (DFT) using B3LYP and LSDA methods with 6-31G basis set combination. The mixing of the fundamental modes was determined with the help of potential energy distribution (PED). The energies of the frontier molecular orbitals have also been determined. Complete NBO analysis was also carried out using B3LYP/6-31G level of theory to find out the intramolecular electronic interactions and their stabilization energy. Thermodynamic properties of the title compound were calculated at the different temperature. Finally, the calculation results were applied to simulate FT-IR and FT-Raman spectra of the title compound which show good agreement with observed spectra. © 2013 Elsevier B.V. All rights reserved.


The keto-enol tautomerism of 2-amino-4-pyrimidinol (APN) and 2-amino-pyrimidine-4(1H)-one (APO) are investigated by vibrational spectroscopy and quantum chemical method. FT-IR and FT-Raman spectra are recorded in the regions of 4000-400 cm-1 and 3500-100 cm-1, respectively for APN. Geometrical parameters, vibrational wavenumbers of APN and APO are predicted by density functional theory (DFT) employing B3LYP level with 6-311++G(d,p) and 6-311++G(2d,p) basis sets. The non-linear optical (NLO) properties of the title molecules are computed. The molecular electrostatic potential (MEP) surface maps are plotted and explained in detail. Natural bond orbital (NBO) analyses have been performed on APN molecule. The significant changes in occupancies and the energies of bonding and antibonding orbital have been explained in detail. Thermodynamic properties (heat capacities, entropies, and enthalpy) and their correlations with temperatures are also obtained from the calculated frequencies of the optimized structures. Reactivity descriptors, Fukui functions and electrophilic sites are found and discussed. © 2012 Elsevier B.V. All rights reserved.


The FT-IR and FT-Raman vibrational spectra of mesityl chloride (2,4,6-trimethylbenzyl chloride) were recorded. The optimized geometry and wavenumbers in the ground state were calculated using density functional (B3LYP, and B3PW91) methods with standard 6-311G(d,p) basis set. The computed B3PW91/6-311G(d,p) results show the best agreement with the experimental values over the other methods. Natural bond orbital analysis of mesityl chloride 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 (μ), polarizability (α), and first hyperpolarizability (β 0) which results also show that the mesityl chloride 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 spe ctra of the title compound, which show excellent agreement with observed spectra. © 2011 Elsevier B.V. All rights reserved.


Balachandran V.,Aa Government Arts College
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2012

This study is a comparative analysis of FT-IR and FT-Raman spectra of vanillin (3-methoxy-4-hydroxybenzaldehyde) and isovanillin (3-hydroxy-4- methoxybenzaldehyde). The molecular structure, vibrational wavenumbers, infrared intensities, Raman scattering activities were calculated for both molecules using the B3LYP density functional theory (DFT) with the standard 6-311++G basis set. The computed values of frequencies are scaled using multiple scaling factors to yield good coherence with the observed values. The calculated harmonic vibrational frequencies are compared with experimental FT-IR and FT-Raman spectra. The geometrical parameters and total energies of vanillin and isovanillin were obtained for all the eight conformers (a-h) from DFT/B3LYP method with 6-311++G basis set. The computational results identified the most stable conformer of vanillin and isovanillin as in the "a" form. Non-linear properties such as electric dipole moment (μ), polarizability (α), and hyperpolarizability (β) values of the investigated molecules have been computed using B3LYP quantum chemical calculation. The calculated HOMO and LUMO energies show that charge transfer occurs within the molecules. © 2012 Elsevier B.V. All rights reserved.


Two purine tautomers of 2-amino-6-chloropurine (ACP), in labeled as N 9H10 and N7H10, were investigated by vibrational spectroscopy and quantum chemical method. The FT-IR and FT-Raman spectra of ACP have been recorded in the regions 4000-400 cm-1 and 3500-100 cm-1, respectively. The measured spectra were interpreted by aid of a normal coordinate analysis following DFT full geometry optimization and vibrational frequency calculations at B3LYP/6-311++G(d,p) level. First-order hyperpolarizability, HOMO and LUMO energies were calculated at same level of theory. The calculated molecular geometry has been compared with the X-ray data. The observed and calculated frequencies were found in good agreement. The obtained NBO data and second-order perturbation energy values to elucidate the Lewis and non-Lewis types of bonding structures in the purine tautomer N 9H10, have indicated the presence of an intramolecular hyperconjucative interaction between lone pair N and N-C bond orbital. © 2012 Elsevier B.V. All rights reserved.


Balachandran V.,Aa Government Arts College
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2011

The Fourier transform infrared (FTIR) and FT Raman spectra of p-toluenesulfonyl isocyanate (p-tosyl isocyanate) have been measured. The molecular geometry, vibrational frequencies, infrared intensities, Raman activities and atomic charges have been calculated by using ab initio HF and density functional theory calculation (B3LYP) with 6-311+G(d,p) basis set. Complete vibrational assignment and analysis of the fundamental modes of the compound were carried out using the observed FTIR and FT Raman data. The thermodynamic functions of the title compound were also performed with the aid of HF/6-311+G(d,p) and B3LYP/6-311+G(d,p) levels of theory. Simulated FTIR and FT Raman spectra for p-tosyl isocyanate showed good agreement with the observed spectra. The calculated HOMO and LUMO energies show that charge transfer occurs within the molecule. The dipole moment (μ), polarizability (α) and the hyperpolarizability (β) values of the investigated molecule have been computed using HF and B3LYP methods. © 2011 Published by Elsevier B.V. All rights reserved.


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

In the present work, we reported a combined experimental and theoretical study on molecular structure, vibrational spectra and NBO analysis of 4-bromo-o-xylene (BOX). The FT-IR (400-4000 cm -1) and FT-Raman spectra (50-3500 cm -1) of BOX were recorded. The molecular geometry, harmonic vibrational frequencies and bonding features of BOX in the ground state have been calculated by using the density functional B3LYP method with 6-311++G(d,p)/6-311+G(d,p) higher basis sets. The energy and oscillator strength are calculated by time-dependent density functional theory (TD-DFT). To determine conformational flexibility, molecular energy profile of BOX was obtained by B3LYP method with 6-311++G(d,p) basis set with respect to selected degree of torsional freedom, which gives three stable conformers. Besides, molecular electrostatic potential (MEP), non-linear properties and NMR analysis were performed at DFT level of theory. © 2012 Elsevier B.V. All rights reserved.


Balachandran V.,Aa Government Arts College | Nataraj A.,Thanthai Hans Roever College | Karthick T.,Vivekanandha College for Women
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2013

FT-Raman and FT-IR spectra for 2-hydroxy-p-toluic acid molecule had been recorded in the regions 3500-100 cm-1 and 4000-400 cm-1, respectively. Vibrational frequencies have been calculated in optimum state by employing density functional theory (DFT) and Hartree Fock (HF) methods with 6-311++G(d,p) basis set in monomeric form. SQM force fields have also been used to calculate potential energy distributions in order to make conspicuous vibrational assignments. Optimized geometries of the molecule had been interpreted and compared. The electric dipole moment and first hyperpolarizability values of the investigated molecule were computed using ab initio and DFT calculations. The calculated HOMO and LUMO energies show that charge transfer occurs within the molecule. Stability of the molecule arising from hyper conjugative interactions, charge delocalization has been analyzed using natural bond analysis. The results show that charge in electron density (ED) in the σ* antibonding orbitals and E(2) energies confirms the occurrence of ICT within the molecule. © 2012 Elsevier B.V. All rights reserved.


Arivazhagan M.,Aa Government Arts College | Jeyavijayan S.,Alagappa Chettiar College of Engineering And Technology
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2011

The molecular vibrations of xanthine were investigated in polycrystalline sample, at room temperature by Fourier transform infrared (FTIR) and FT-Raman spectroscopies. The spectra of the molecule have been recorded in the regions 4000-50 cm-1 and 3500-100 cm-1, respectively. Theoretical information on the optimized geometry, harmonic vibrational frequencies, infrared and Raman intensities were obtained by means of ab initio Hartree-Fock (HF) and density functional theory (DFT) gradient calculations with complete relaxation in the potential energy surface using 6-311++G(d,p) basis set. The vibrational frequencies which were determined experimentally from the spectral data are compared with those obtained theoretically from ab initio and DFT calculations. A close agreement was achieved between the observed and calculated frequencies by refinement of the scale factors. The infrared and Raman spectra were also predicted from the calculated intensities. Thermodynamic properties like entropy, heat capacity, zero point energy have been calculated for the molecule. Unambiguous vibrational assignment of all the fundamentals was made using the potential energy distribution (PED). © 2010 Elsevier B.V. All rights reserved.


Arivazhagan M.,Aa Government Arts College | Jeyavijayan S.,Alagappa Chettiar College of Engineering And Technology
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2011

The Fourier-transform infrared spectrum of 1,2-dichloro-4-nitrobenzene (DCNB) was recorded in the region 4000-400 cm-1. The Fourier-transform Raman spectrum of DCNB was also recorded in the region 3500-50 cm-1. Quantum chemical calculations of energies, geometrical structure and vibrational wavenumbers of DCNB were carried out by ab initio HF and density functional theory (DFT/B3LYP) method with 6-31+G(d,p) basis set. The difference between the observed and scaled wavenumber values of most of the fundamentals is very small. The values of the total dipole moment (μ) and the first-order hyperpolarizability (β) of the investigated compound were computed using ab initio quantum mechanical calculations. The calculated results also show that the DCNB might have microscopic nonlinear optical (NLO) behavior with non-zero values. A detailed interpretation of the infrared and Raman spectra of DCNB is also reported based on total energy distribution (TED). The calculated HOMO and LUMO energies shows that charge transfer occur within the molecule. The theoretical FT-IR and FT-Raman spectra for the title compound have also been constructed. © 2011 Elsevier B.V.

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