Showing papers by "Hema Tresa Varghese published in 2011"

Spectroscopic investigations and computational study of sulfur trioxide–pyridine complex

Abstract: The Fourier transform infrared (FT-IR) and FT-Raman spectra of sulfur trioxide-pyridine complex were recorded and analyzed. The potential-dependent surface-enhanced Raman scattering (SERS) was recorded from an electrochemically roughened silver electrode. The vibrational wave numbers of the compound were computed using the Hartree – Fock/6-31G ∗ basis and compared with the experimental values. The presence of strong pyridine ring vibrations in the SERS spectrum reveals the interaction between the pyridine ring and the silver surface. The molecule is adsorbed on the silver surface with the pyridine ring in a tilted orientation. The direction of charge-transfer contribution to the SERS is discussed from the frontier orbital theory. The value of the calculated first hyperpolarizability is comparable to those reported for similar structures, which makes this molecule an attractive object for future studies of nonlinear optics. The optimized geometrical parameters of the title compound are in agreement with similar reported structures. Copyright c � 2011 John Wiley & Sons, Ltd.

Comparison of Langmuir and Harkins-Jura Adsorption Isotherms for the Determination of Surface Area of Solids

Abstract: Batch experiments were carried out for the adsorption of aniline on activated charcoal and titanium dioxide from toluene at 35, 40, 45, 50 and 55°C. The adsorption of aniline on charcoal from toluene (ACT) was of L3 type and aniline on titanium dioxide from toluene (ATT) was of L2 type as per Giles classification. The experimental data were analyzed with Langmuir and Harkins-Jura adsorption isotherms. The Harkins-Jura equation was obeyed by all systems for the entire concentration range studied, where the Langmuir equation fails. All Harkins-Jura plots contained two intersecting straight lines. The point of intersection of the two lines relate to completion of a monolayer. From these monolayer values the specific surface areas of adsorbents were calculated. By Harkins-Jura relative method the surface areas of the adsorbents were also obtained by comparison of the slopes of the straight lines, without resorting to the ambiguous parameters like molecular area and unreliable monolayer values.

FT-IR and Computational Study of Sulphaguanidine

Abstract: The vibrational wavenumbers of sulphaguanidine were calculated using Gaussian03 software at different levels and compared with experimentally observed data. The predicted infrared intensities, Raman activities and first hyperpolarizability are reported. The calculated geometrical parameters (DFT) are in agreement with that of similar derivatives. The potential energy scan studies for different torsion angles are also reported. The splitting of NH stretching wavenumber in the infrared spectrum indicates the weakening of the NH bond.

Vibrational spectroscopic studies and computational study of 1,2-diphenyl-4-n-butyl-3,5-pyrazolidinedione

Abstract: FT-IR and FT-Raman spectra of 1,2-diphenyl-4-n-Butyl-3,5-pyrazolidinedione (Phenylbutazone) were recorded and analyzed. The vibrational wavenumbers were computed using HF/6-31G(d) and B3LYP/6-31G(d) basis sets and compared with experimental data. The first hyperpolarizability, infrared intensities and Raman activities are also reported. The geometrical parameters of the title compound obtained from theoretical calculations are in agreement with that of reported similar derivatives. The first hyperpolarizability is comparable with reported values of similar derivatives and is an attractive molecule for future applications in non-linear optics. The variation in C-N bond lengths suggests an extended πelectron delocalization over the pyrazolidinedione moiety which is responsible for the nonlinearity of the molecule.

FT-IR, FT-Raman spectroscopy and computational study of(E)-4-((anthracen-9-ylmethylene)amino)-N-carbamimidoylbenzenesulfonamide

Abstract: The infrared and Raman spectra of (E)-4-((anthracen-9-ylmethylene)amino)-N-carbamimidoylbenzene sulfonamide have been recorded and analysed. Geometry and harmonic vibrational wavenumbers were calculated theoretically using Gaussian03 set of quantum chemistry codes. The data obtained from vibrational wavenumber calculations are used to assign vibrational bands found in infrared and Raman spectra of the studied molecule. The red-shift of the NH stretching band in the infrared spectrum from the computed wavenuinber indicates the weakening of the NH bond. The NH stretching band has split into a doublet in the IR spectrum owing to the Davydov coupling between neighbouring units. The geometrical parameters of the title compound are in agreement with the reported similar derivatives. The calculated first hyperpolarizability is comparable with the reported value of similar structures and may be an attractive object for further studies on non-linear optics. The important thermodynamical parameters are also reported.

IR, Raman and Ab-initio Calcualtions of Glycolic Acid

Abstract: Fourier-transform-Raman and infrared spectrum of glycolic acid were recorded and analyzed. The vibrational wavenumbers were examined theoretically using the Gaussian03 set of quantum chemistry codes. The first hyperpolarizability, predicted infrared intensities and Raman activities are reported. The calculated first hyperpolarizability makes this compound an attractive object for future studies of nonlinear optics. The experimental frequencies are in agreement with the calculated scaled values.

FT-IR and Computational Study of 4-{((2Z)-1,7,7- Trimethylbicyclo(2.2.1)hept-2-ylidene)amino}Benzoic Acid

Abstract: Fourier transform infrared spectrum of 4-{[(2Z)-1,7,7-trimethylbicyclo[2.2.1]hept-2ylidene]amino}benzoic acid was recorded and analyzed. The vibrational wavenumbers were examined theoretically using the Gaussian03 set of quantum chemistry codes. The calculated first hyperpolarizability is reported and the title compound is an attractive object for future studies of nonlinear optics. Optimized geometrical parameters of the title compound are in agreement with that of similar reported structures. Predicted infrared intensities are also reported.

Ab Initio Modeling of the Structural Defects in Amides

Abstract: A series of models was constructed with varying lengths of conjugated chain containing different carbon atoms on each side of a core containing an amide group. The important amide bands, geometrical parameters and thermal parameters are reported. The theoretical calculations were done at the DFT level using Gaussian03 software.

FT-IR, FT-Raman and Computational Study of Ethyl Methyl Ketone Semicarbazone

Abstract: FT-IR and FT-Raman spectra of ethyl methyl ketone semicarbazone were recorded and analyzed. The vibrational wavenumbers were computed using HF/6-31G*, B3PW91/6-31G* and B3LYP/6-31G* basis and compared with experimental data. The first hyperpolarizability, infrared intensities and Raman activities are reported. The calculated first hyperpolarizability is comparable with the reported values of similar derivatives and is an attractive object for future studies of non-linear optics. The extended π-electron delocalization over the carbazone moiety is responsible for the nonlinearity of the molecule. The geometrical parameters of the title compound are in agreement with that of similar derivatives. The red shift of the NH stretching wavenumber in the infrared spectrum from the computed wavenumber indicates the weakening of the NH bond resulting in proton transfer to the neighboring oxygen atom.