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Ghāziābād, India

Alcolea Palafox M.,Complutense University of Madrid | Rastogi V.K.,Aryan Institute of Technology | Kumar S.,Aryan Institute of Technology | Joe H.,Mar Ivanios College
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2013

An accurate assignment of the IR spectrum in Ar matrix of 5-bromocytosine and of the IR and Raman spectra in the solid state was carried out. For this purpose Density functional calculations (DFTs) were performed to clarify wavenumber assignments of the experimental observed bands. The calculated values were scaled using scaling equations and they were compared with IR and Raman experimental data. Good reproduction of the experimental wavenumbers is obtained and the% error is very small in the majority of cases. In the isolated state all the tautomer forms of 5-bromocytosine were determined and optimized. The wavenumbers corresponding to C1 and C2b tautomers were identified and assigned in the IR experimental spectrum reported in Ar matrix. Our study confirms the existence of at least two tautomers, the amino-oxo and the amino-hydroxy in the isolated state. In the solid state the FT-IR and FT-Raman spectra of 5-bromocytosine in the powder form were recorded in the region 400-4000 cm -1 and 50-3500 cm-1, respectively. The unit cell found in the crystal was simulated as a tetramer form in three tautomers. Thus, it has been possible to assign all the 33 normal modes of vibration. The study indicates that the features, that are the characteristic of the vibrational spectra of cytosine, are retained by the spectra of 5-bromocytosine and it exists in the solid phase in the amino-oxo form. © 2013 Elsevier B.V. All rights reserved. Source


Balachandran V.,Aa Government Arts College | Santhi G.,Government Arts College | Karpagam V.,Srinivasan Polytechnic College | Rastogi V.K.,Aryan Institute of Technology
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2014

The FT-IR and Raman spectra of 2-amino-5-nitrobenzophenone (ANBP) molecule have been recorded using Brucker IFS 66 V spectrometer in the range of 4000-100 cm-1. The molecular geometry and vibrational frequencies in the ground state are calculated using the Hartree-Fock (HF) and B3LYP with 6-311+G(d) basis set. The computed values of frequencies are scaled using a suitable scale factor to yield good coherence with the observed values. The isotropic HF and DFT analysis showed good agreement with experimental observations comparison of the fundamental vibrational frequencies with calculated results by HF and B3LYP methods indicates that B3LYP/6-311+G(d) is superior to HF/6-311+G(d) for molecular vibrational problems. The electric dipole moment (μ) and first hyper polarizability (β) values of the investigated molecule were computed using density functional theory calculations. Stability of the molecule arising from hyperconjucative interactions leading to its bioactivity, charge delocalization have been analyzed using natural bond orbital (NBO) analysis. The calculated HOMO-LUMO energies shows that charge transfer occur within the molecule. The thermodynamic functions (heat capacity, internal heat energy, Gibbs energy and entropy) from spectroscopic data by statistical methods were obtained for the range of temperature 100-1000 K. The observed and calculated frequencies are found to be in good agreement. © 2013 Elsevier B.V. All rights reserved. Source


Ortiz S.,Complutense University of Madrid | Alcolea Palafox M.,Complutense University of Madrid | Rastogi V.K.,Aryan Institute of Technology | Akitsu T.,Tokyo University of Science | And 2 more authors.
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2013

A Raman and FT-IR study of the biomolecule 5-chlorouracil in the solid state was carried out. The unit cell found in the crystal was simulated as a tetramer form by density functional calculations. They were performed to clarify the assignments of the experimentally observed bands in the spectra. Calculations in the monomer form and comparisons with the experimental data in Ar matrix were also carried out. The error in the calculated frequencies was analyzed and reduced by using scaling equations and scaling factors deduced from the uracil molecule. The calculations with the B3LYP method and with the 6-31G(d,p) and 6-311+G(2d,p) basis set, appear in general to be useful, when combining with a scaling equation procedure or with the specific scale factors, for interpretation of the general features of the IR and Raman spectra. The scaled values were used in the reassignment of the IR and Raman experimental bands. Comparison of the results with those determined in uracil and 5-halogenated derivatives were performed. The substitution at 5-position of the uracil ring by a chlorine atom has a little effect on the geometric parameters. © 2013 Elsevier B.V. All rights reserved. Source


Xavier T.S.,St. Xaviers HSS Peyad | Hubert Joe I.,Center for Molecular and Biophysics Research | Palafox M.A.,Complutense University of Madrid | Kumar S.,University Campus | And 3 more authors.
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2013

An accurate assignment of the vibrational spectra of 4-Formylbenzoic acid in solid state was carried out. For this purpose density functional calculations (DFT) were performed to clarify wavenumber assignments of the experimentally observed bands for the first time. A scaling of the wavenumbers was carried out to improve the calculated values. Good reproduction of the experimental wavenumbers is obtained and the % error is very small in the majority of cases. The NBO analysis was carried out, and it reveals hyper conjugative Interaction, iCT and stabilization of molecules. © 2013 Elsevier B.V. All rights reserved. Source


Kattan D.,Complutense University of Madrid | Alcolea Palafox M.,Complutense University of Madrid | Kumar S.,Aryan Institute of Technology | Manimaran D.,Center for Molecular and Biophysics Research | And 2 more authors.
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2014

FT-IR and FT-Raman spectra of 2,4-dichlorobenzonitrile at room temperature have been recorded in the regions 200-3500 cm-1 and 0-3400 cm-1, respectively. The observed vibrational bands were analyzed and assigned to different normal modes of the molecule according to the Wilson's notation. Density functional calculations were performed to support our frequency assignments. Specific scale equations deduced from the benzene molecule were employed to improve the calculated values. For the majority of the normal modes, the deviations between the corresponding experimental and scaled theoretical wavenumbers are located in the expected range. A correct characterization of each normal mode is of vital importance in the assignment of the observed bands, and the same has been successfully done by the aid of Potential Energy Distributions (PEDs) calculated separately for each normal mode of 2,4-dichlorobenzonitrile. The molecular structure was optimized and several thermodynamic parameters were determined. HOMO and LUMO orbital energy analysis were carried out. © 2013 Elsevier B.V. All rights reserved. Source

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