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Balachandran V.,Aa Government Arts College | Nataraj A.,Thanthai Hans Roever College | Karthick T.,Vivekanandha College for Women
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2013

FT-Raman and FT-IR spectra for 2-hydroxy-p-toluic acid molecule had been recorded in the regions 3500-100 cm-1 and 4000-400 cm-1, respectively. Vibrational frequencies have been calculated in optimum state by employing density functional theory (DFT) and Hartree Fock (HF) methods with 6-311++G(d,p) basis set in monomeric form. SQM force fields have also been used to calculate potential energy distributions in order to make conspicuous vibrational assignments. Optimized geometries of the molecule had been interpreted and compared. The electric dipole moment and first hyperpolarizability values of the investigated molecule were computed using ab initio and DFT calculations. The calculated HOMO and LUMO energies show that charge transfer occurs within the molecule. Stability of the molecule arising from hyper conjugative interactions, charge delocalization has been analyzed using natural bond analysis. The results show that charge in electron density (ED) in the σ* antibonding orbitals and E(2) energies confirms the occurrence of ICT within the molecule. © 2012 Elsevier B.V. All rights reserved. Source


Nataraj A.,Thanthai Hans Roever College | Balachandran V.,Aa Government Arts College | Karthick T.,Vivekanandha College for Women | Karabacak M.,Afyon Kocatepe University | Atac A.,Celal Bayar University
Journal of Molecular Structure | Year: 2012

The FT-IR and FT-Raman spectra of 3,5-pyridinedicarboxylic acid (dinicotinic acid, C 7H 5NO 4) in the solid phase were recorded. The fundamental vibrational wavenumbers, intensities of vibrational bands and the optimized geometrical parameters of the compound are evaluated using HF and DFT (B3LYP) methods with 6-311G(d) basis set. The difference between the observed and scaled wavenumber values of most of the fundamentals is very small. The computed dimer parameters also show agreement with experimental data. The complete assignments were performed on the basis of the total energy distribution (TED). Stability of the molecule arising from hyperconjugative interactions, charge delocalization have been analyzed using natural bond orbital (NBO) analysis. UV-visible spectrum of the compound was recorded in the region 200-400 nm and the electronic properties HOMO and LUMO energies were measured by time-dependent TD-DFT approach. Thermodynamic properties (heat capacity, entropy and enthalpy) of the title compound at different temperatures were calculated. © 2012 Elsevier B.V. All rights reserved. Source


Karthick T.,Vivekanandha College for Women | Balachandran V.,Aa Government Arts College | Perumal S.,St Hindu College | Nataraj A.,Thanthai Hans Roever College
Journal of Molecular Structure | Year: 2011

The stable isomer of N-(2 bromoethyl) phthalimide (NBEP) is determined. FT-IR (4000-400 cm-1) and FT-Raman (3500-100 cm-1) spectra were recorded on the solid phase of the molecule. Optimized geometrical parameters, vibrational wavenumbers of the stable isomer of NBEP are predicted by DFT/B3LYP/6-311++G(d,p). Reliable vibrational assignments associated with this molecule is made on the basis of total energy distribution (TED) results. The non-linear optical properties such as dipole moment, polarizability and first order hyperpolarizability of the title molecule are determined. Density plots over the highest occupied molecular orbitals (HOMO) and lowest unoccupied molecular orbitals (LUMO) energy surface directly identifies the donor and acceptor atoms in the molecule. It also provides information about the charge transfer within the molecule. To obtain chemical reactivity of the molecule, the molecular electrostatic potential (MEP) surface map is plotted over the optimized geometry of the molecule. Furthermore, reactive electrophilic and nucleophilic sites in the MEP surface are compared with the fitting point charges to electrostatic potential. © 2011 Elsevier Inc. All rights reserved. Source


Karthick T.,Vivekanandha College for Women | Balachandran V.,Aa Government Arts College | Perumal S.,St Hindu College | Nataraj A.,Thanthai Hans Roever College
Journal of Molecular Structure | Year: 2011

In this work, FT-IR and FT-Raman spectra are recorded on the solid phase of 5-nitrosalicylic acid (abbreviated as 5-NSA). The energies of all possible conformers obtained from DFT theory with 6-311++G(d,p) basis set identified the most stable conformer of 5-NSA as C6 form. Optimized geometrical parameters, vibrational assignments, HOMO-LUMO energies and NBO calculations are performed on the stable monomer and dimer structure of 5-NSA using the same level of theory. Second order perturbation energies and electron density (ED) transfer from filled lone pairs of Lewis base to unfilled Lewis acid sites of 5-NSA are discussed on the basis of NBO analysis. Inter- and intramolecular hydrogen bonds exist between COOH and OH group, give the evidence for the formation of dimer entities in the title molecule. The variations in bond lengths, ED and vibrational wavenumbers of 5-NSA dimer are being discussed. The spectroscopic and theoretical results are compared to the corresponding properties for 5-NSA monomer and dimer of C6 conformer. Reliable vibrational modes associated with 5-NSA are made on the basis of total energy distribution (TED) results obtained from scaled quantum mechanical (SQM) method. © 2011 Elsevier Inc. All rights reserved. Source


Nataraj A.,Thanthai Hans Roever College | Balachandran V.,Aa Government Arts College | Karthick T.,Vivekanandha College for Women
Journal of Molecular Structure | Year: 2013

In this work, the vibrational spectral analysis was carried out using Raman and infrared spectroscopy in the range 4000-400 cm-1 and 3500-100 cm-1, respectively, for the 2-hydroxy-5-bromobenzaldehyde (HBB). The experimental spectra were recorded in the solid phase. The fundamental vibrational frequencies and intensity of vibrational bands were evaluated using density functional theory (DFT) with the standard B3LYP/6-311G++(d,p) method and basis set. Normal co-ordinate calculations were performed with the DFT force field corrected by a recommended set of scaling factors yielding fairly good agreement between observed and calculated frequencies. Simulation of infrared and Raman spectra utilizing the results of these calculations led to excellent overall agreement with the observed spectral patterns. The complete assignments were performed on the basis of the potential energy distribution (PED) of the vibrational modes, calculated with scaled quantum mechanics (SQM) method. The optimized geometric parameters (bond lengths and bond angles) were compared with experimental values of related compound. The stability of the molecule arising from hyper conjugative interactions and the charge delocalization has been analyzed using natural bond orbital (NBO) analysis. The directly calculated ionization potential (IP), electron affinity (EA), electronegativity (χ), electrophilicity index (ω), hardness (η), chemical potential (μ), and first electron excitation (τ) are all correlated with the HOMO and LUMO energies with their molecular properties. These show that charge transfer occurs within the molecule. Furthermore, molecular electrostatic potential maps (MESP) of the molecule have been calculated. © 2012 Elsevier B.V. All rights reserved. Source

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