Entity

Time filter

Source Type


Balachandran V.,Center for Research | Lalitha S.,P.A. College | Rajeswari S.,P.A. College | Rastogi V.K.,Rd Foundation Group Of Institutions
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2014

The experimental FT-IR (4000-400 cm-1) and FT-Raman (3500-100 cm-1) spectra of p-(p-hydroxyphenoxy) benzoic acid have been recorded. Quantum chemical calculations of energies, geometries, and vibrational wavenumbers of p-(p-hydroxyphenoxy) benzoic acid (PPHPBA) are carried out using HF and DFT/B3LYP methods with 6-311G (d,p) basis set. The optimized geometrical parameters obtained by B3LYP method show a good agreement with experimental data. The difference between the observed and scaled wave number values of most of the fundamentals is very small. The complete assignments were performed on the basis of the potential energy distribution (PED) of the vibrational modes calculated with scaled quantum mechanical method. The calculated HOMO and LUMO energies allow the calculation of atomic and molecular properties and they also show that charge transfer occurs in the molecule. A detailed molecular picture of PPHPBA and its intermolecular interactions were obtained from NBO analysis. The temperature dependence of various thermodynamic parameters was also studied. The paramagnetic behavior of the molecule under consideration has been investigated and the variation of paramagnetic susceptibility with temperature has been studied. © 2013 Elsevier B.V. All rights reserved. Source


Ortiz S.,Complutense University of Madrid | Alvarez-Ros M.C.,Complutense University of Madrid | Alcolea Palafox M.,Complutense University of Madrid | Rastogi V.K.,Rd Foundation Group Of Institutions | And 2 more authors.
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2014

A Raman and IR study of the biomolecule 6-chlorouracil was carried out in the solid state. The unit cell found in the crystal was simulated as a tetramer form by density functional calculations. Specific scale factors and scaling equations deduced from uracil molecule were employed in the predicted wavenumbers of 6-chlorouracil. The scaled wavenumbers were used in the reassignment of the IR and Raman experimental bands. Good reproduction of the experimental wavenumbers is obtained and the % error is very small in the majority of cases. A comparison between the molecular structure and charge distribution of 6-chlorouracil and 5-chlorouracil molecules was presented. The effect of the hydration with the PCM model in the molecular structure and charges was discussed. The optimum tautomers of 6-chlorouracil were optimized and analyzed. Six of them were related to those of uracil molecule. The effect of the halogen substitution in the sixth position of the pyrimidine ring in the stability of the different tautomers was evaluated. HOMO and LUMO orbital energy analysis were carried out. © 2014 Elsevier B.V. All rights reserved. Source


Alcolea Palafox M.,Complutense University of Madrid | Bhat D.,Rd Foundation Group Of Institutions | Goyal Y.,Rd Foundation Group Of Institutions | Ahmad S.,Aligarh Muslim University | And 2 more authors.
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2015

The experimental FT-IR and FT-Raman spectra of 2,5-dichlorobenzonitrile molecule were recorded at room temperature, and the results compared with quantum chemical theoretical values using MP2 and DFT methods. Molecular geometry, vibrational wavenumbers and thermodynamic parameters were calculated. With the help of specific scaling procedures for the computed wavenumbers, the experimentally observed FTIR and FT-Raman bands were analyzed and assigned to different normal modes of the molecule. Most of the modes have wavenumbers in the expected range and the error obtained was in general very low. Several general conclusions were deduced. The NBO analysis has been done and Molecular Electrostatic Potential (MEP) has been plotted. © 2014 Elsevier B.V. All rights reserved. Source

Discover hidden collaborations