Spectrophysics Research Laboratory

Chennai, India

Spectrophysics Research Laboratory

Chennai, India
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Gnanasambandan T.,SCSVMV 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.,SCSVMV 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.


Gnanasambandan T.,SCSVMV University | Gunasekaran S.,Spectrophysics Research Laboratory | Seshadri S.,Ln Government Arts College
Oriental Journal of Chemistry | Year: 2013

The FT-IR and FT-Raman vibrational spectra of selegiline were recorded. The optimized geometry and wavenumbers in the ground state were calculated using density functional (B3LYP) method with standard 6-31G(d,p) basis set. The computed B3LYP/6-31G(d,p) results show the best agreement with the experimental values over the other methods. Natural bond orbital analysis of selegiline 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 (α), polarizability (α), and first hyperpolarizability (β0) which results also show that the selegiline 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 spectra of the title compound, which show excellent agreement with observed spectra.


Gnanasambandan T.,SCSVMV University | Gunasekaran S.,Spectrophysics Research Laboratory | Seshadri S.,Lngovt Arts College
Journal of Molecular Structure | Year: 2013

The complete vibrational assignment and analysis of the fundamental modes of carbimazole (CBZ) was carried out using the experimental FTIR, FT-Raman and UV-Vis data and quantum chemical studies. The observed vibrational data were compared with the wavenumbers derived theoretically for the optimized geometry of the compound from the DFT-B3LYP gradient calculations employing 6-31G(d,p) and 6-311++G(d,p) basis sets. 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 properties such as electric dipole moment and first hyperpolarizability of CBZ have been computed using B3LYP quantum chemical calculation. Finally, the Mulliken population analysis on atomic charges of the title compound has been calculated. © 2013 Elsevier B.V. All rights reserved.


Gnanasambandan T.,SCSVMV University | Gunasekaran S.,Spectrophysics Research Laboratory | Seshadri S.,Arignar Anna Government Arts College
Research Journal of Chemistry and Environment | Year: 2013

The FTIR and FT Raman spectrum of propylthiouracil have been recorded in the regions 4000 - 400 cm-1 and 3500-100 cm-1 respectively. The optimized geometry, wave number and intensity of the vibrational bands of propylthiouracil were obtained by ab initio and DFT levels of theory with complete relaxation in the potential energy surface using 6-31G (d,p) basis set. A complete vibrational assignment aided by the theoretical harmonic frequency analysis has been proposed. 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 bar type spectrograms.


Udhayakala P.,Drmgr Educational And Research Institute | Jayanthi A.,Panimalar Institute of Technology | Rajendiran T.V.,Pachaiyappas College | Gunasekaran S.,Spectrophysics Research Laboratory
Research on Chemical Intermediates | Year: 2013

Density functional theory at the B3LYP/6-31G(d,p) basis set level was performed on three thiadiazolines, namely 4-chloro-N-(5-phenyl-1,3,4-thiadiazol- 2(3H)-ylidene)aniline (TD01), 4-chloro-N-(5-(4-methoxyphenyl)-1,3,4-thiadiazol- 2(3H)-ylidene)aniline (TD02), and 2-(5-(4-chlorophenylimino)-4,5-dihydro-1,3,4- thiadiazol-2-yl) phenol (TD03), and the inhibitive effect of these thiadiazolines against the corrosion of mild steel in acidic medium is elucidated. The calculated quantum chemical parameters correlated to the inhibition efficiency are EHOMO (highest occupied molecular orbital energy), ELUMO (lowest unoccupied molecular orbital energy), the energy gap (ΔE) hardness (η), softness (S), dipole moment (μ), electron affinity (EA) ionization potential (IE), the absolute electro negativity (χ), and the fraction of electron transferred (ΔN). The decreasing order of %IE of the thiadiazolines studied was found to be in agreement with experimental corrosion inhibition efficiencies. The local reactivity has been analyzed through the condensed Fukui function and local softness indices using population analysis. © 2012 Springer Science+Business Media B.V.


PubMed | St Peters University and SpectroPhysics Research Laboratory
Type: | Journal: Journal of pharmaceutical and biomedical analysis | Year: 2017

Diabetes mellitus is chronic metabolic disorder, resulting from insulin deficiency, characterized by hyperglycemia altered metabolism of carbohydrates, proteins and lipids and an increased risk of vascular complications. There are different classes of anti-diabetic drugs in allopathic system of medicine. Metformin (dimethyl biguanide) is a blood glucose lowering agent used in the treatment of non-insulin dependent diabetes mellitus. Almost in all diseases the blood serves as the primary metabolic transport system in the body. Its composition is the preferred indicator with respect to the pathophysiological condition of the patient. Instead of analyzing blood to diagnose diabetes, hair could be used to detect diabetes using FTIR-ATR technique. The most important components of hair are fibrous proteins (keratins), melanins, glycogen, and lipids. Hair follicles are located 3-4mm below the surface of the skin and are surrounded by rich blood capillary system. In the present study, ten diabetic subjects were considered to evaluate the efficacy of metformin hydrochloride for the treatment of diabetes mellitus using FTIR-ATR spectroscopy. The spectra of diabetic hair fibre samples have been recorded in the mid infrared region of 4000-450cm


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.


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.


Udhayakala P.,Dr. M.G.R. Educational and Research Institute | Maxwell Samuel A.,Nazareth College | Rajendiran T.V.,Pachaiyappas College | Gunasekaran S.,Spectrophysics Research Laboratory
Der Pharma Chemica | Year: 2013

Corrosion inhibition performance of three Phenyltetrazole substituted compounds, namely 5-phenyl-1H-tetrazole (PT), 5-p-tolyl-1H-tetrazole (M-PT) and 5-(4-methoxyphenyl)-1H-tetrazole (MO-PT) on mild steel was evaluated by quantum chemical calculations based on density functional theory (DFT) method at the B3LYP/6-31G(d,P) basis set level in order to investigate the relationship between their molecular and electronic structure and inhibition efficiency. The quantum chemical properties most relevant to their potential action as corrosion inhibitors such as EHOMO, ELUMO, energy gap (ΔE), dipole moment (μ), hardness (η), softness (S), the absolute electronegativity (χ), the fractions of electrons transferred (ΔN) and the electrophilicity index (ω) were calculated. The local reactivity has been analyzed through the Fukui function and condensed softness indices in order to compare the possible sites for nucleophilic and electrophilic attacks. The theoretical results obtained using DFT based reactivity indexes, were found to be consistent with the experimental outcomes.

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