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Udhayakala P.,Drmgr Educational And Research Institute | Jayanthi A.,Panimalar Institute of Technology | Rajendiran T.V.,Pachaiyappas College | Gunasekaran S.,Spectrophysics Research Laboratory
International Journal of ChemTech Research | Year: 2011

The FT-IR (4000-400 cm -1) and FT- Raman (4000-100 cm -1) spectra of 2-chloro-4-nitroaniline (2Cl4NA) have been recorded using Bruker IFS 66 V spectrometer. An ab initio HF(HF/6-311G(d,p) and DFT(B3LYP/6-311G(d,p)) calculations have been performed giving energies, optimized structures, harmonic vibrational frequencies,IR intensities and Raman activities. The study is extended to the HOMO - LUMO analysis to calculate the energy gap, ionization potential, electron affinity, global hardness,chemical potential and global electrophilicity and thermodynamic properties of 2Cl4NA. A complete vibrational assignment aided by the theoretical harmonic frequency analysis has been proposed. The calculated HOMO and LUMO energies show the charge transfer occurs in the molecule. The harmonic vibrational frequencies calculated have been compared with experimental FTIR and FT Raman spectra. The observed and the calculated frequencies are found to be in good agreement. The experimental spectra also coincide satisfactorily with those of theoretically constructed simulated spectrograms.

Gnanasambandan T.,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.,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.

Valarmathi D.,Queen Marys College | Abraham L.,Ethiraj College | Gunasekaran S.,Spectrophysics Research Laboratory
Indian Journal of Pure and Applied Physics | Year: 2010

Calcium oxalate monohydrate (COM), a urinary stone has been formed by single diffusion gel technique. The grown crystal is analyzed by Fourier Transform Infrared Spectroscopy (FTIR). The spectrum reveals various vibrational modes characterizing particular functional group. The investigation confirms the existence of oxalate group and water molecule in COM.

Sangeetha V.,Dgvaishnav College | Govindarajan M.,MGGA College | Kanagathara N.,Vel Tech Dr.RR & Dr.SR Technical University | Marchewka M.K.,Institute of Low Temperature And Structure Research | And 2 more authors.
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2014

A new organic-organic salt, 3-nitrophenol-1,3,5-triazine-2,4,6-triamine (2/1) (3-NPM) has been synthesized by slow evaporation technique at room temperature. Single crystal X-ray diffraction analysis reveals that 3-NPM crystallizes in orthorhombic system with centrosymmetric space group Pbca and the lattice parameters are a = 15.5150(6) Å, b = 12.9137(6) Å, c = 17.8323(6) Å, α = β = γ = 90 and V = 3572.8(2) (Å)3. The geometry, fundamental vibrational frequencies are interpreted with the aid of structure optimization and normal coordinate force field calculations based on density functional theory (DFT) B3LYP/6-311G(d,p) method. IR and Raman spectra of 3-NPM have been recorded and analyzed. The complete vibrational assignments are made on the basis of potential energy distribution (PED). The electric dipole moment, polarizability and the first order hyperpolarizability values of the 3-NPM have been calculated. 1H and 13C NMR chemical shifts are calculated by using the gauge independent atomic orbital (GIAO) method with B3LYP method with 6-311G (d,p) basis set. Moreover, molecular electrostatic potential (MEP) and thermodynamic properties are performed. Mulliken and Natural charges of the title molecule are also calculated and interpreted. Thermal decomposition behavior of 3-NPM has been studied by means of thermogravimetric analysis. The dielectric measurements on the powdered sample have been carried out and the variation of dielectric constant and dielectric loss at different frequencies of the applied field has been studied and the results are discussed in detail. © 2013 Elsevier B.V. All rights reserved.

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