S. Sampathkrishnan

Quantum mechanical study of the structure and spectroscopic, first order hyperpolarizability, Fukui function, NBO, normal coordinate analysis of Phenyl-N-(4-Methyl Phenyl) Nitrone

The title compound, Phenyl-N-(4-Methyl Phenyl) Nitrone (PN4MPN) was synthesized and characterized by FT-IR, FT-Raman and (1)HNMR, (13)CNMR spectral analysis. The molecular geometry, harmonic vibrational frequencies and bonding features of the title compound in the ground state are computed at the Hartree-Fock/6-311++G(d,p) and three parameter hybrid functional Lee-Yang-Parr/6-311++G(d,p) levels of theory. The calculated results show that the predicted geometry can well reproduce the structural parameters. 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 (SQMF). The calculated HOMO and LUMO energies confirm that charge transfer occurs within the molecule. The dipole moment (μ), polarizability (α) and hyperpolarizability (β) of the investigated molecule is calculated by using HF/6-311++G(d,p) and B3LYP/6-311++G(d,p) methods on the finite field approach. Besides, Molecular Electrostatic Potential (MEP), Natural Bond Orbital analysis (NBO) and thermodynamical properties are described from the computational process. The electron density-based local reactivity descriptor such as Fukui functions are calculated to explain the chemical selectivity or reactivity site in PN4MPN. Finally, the calculations are applied to simulated FT-IR and FT-Raman spectra of the title compound which show good agreement with observed spectra.

Synthesis, spectroscopic (FT-IR, FT-Raman, 13C, 1H, UV) study, first order hyperpolarizability, NBO analysis, HOMO and LUMO analysis of 2(2-Hydroxyphenyl)-N-(4-Methylphenyl) Nitrone.

The title compound, 2(2-Hydroxyphenyl)-N-(4-Methylphenyl) Nitrone (2HPN4MPN) was synthesized and characterized by FT-IR, FT-Raman, UV-Vis and (1)HNMR, (13)CNMR spectral analysis. The molecular geometry, harmonic vibrational frequencies and bonding features of the title compound in the ground state are computed at three parameter hybrid functional Lee-Yang-Parr/6-311++G(d,p) levels of theory. The most stable conformer of 2HPN4MPN is identified from the computational results. 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 (SQMF). The UV-Vis spectrum was recorded in chloroform solution. The energy and oscillator strength calculated by time-dependent density functional theory (TD-DFT) complements the experimental findings. The calculated HOMO and LUMO energies confirm that charge transfer occurs within the molecule. In addition, DFT calculations of the compound, Molecular Electrostatic Potential (MEP), Natural Bond Orbital analysis (NBO) and non-linear optical (NLO) properties are performed at B3LYP/6-311++G(d,p) level of theory. Finally, the calculations are applied to simulated FT-IR and FT-Raman spectra of the title compound which show good agreement with observed spectra.

Synthesis, growth, structural, thermal and optical studies of pyrrolidinium-2-carboxylate-4-nitrophenol single crystals.

Organic nonlinear optical material, pyrrolidinium-2-carboxylate-4-nitrophenol (PCN) was synthesized and single crystals were grown by slow evaporation solution growth method. Single crystal X-ray diffraction analysis confirmed the structure and lattice parameters of PCN crystals. Infrared, Raman and NMR spectral analyses were used to elucidate the functional groups present in the compound. The thermal behavior of synthesized compound was studied by thermogravimetric and differential scanning calorimetry (TG-DSC) analyses. The photoluminescence property was studied by exciting the crystal at 360 nm. The relative second harmonic generation (SHG) efficiency of grown crystal was estimated by using Nd:YAG laser with fundamental wavelength of 1,064 nm.

Molecular structure, vibrational spectra, first order hyper polarizability, NBO and HOMO–LUMO analysis of 2-amino-5-bromo-benzoic acid methyl ester

An organic crystal of 2-amino-5-bromobenzoic acid methyl ester [abbreviated at 2A5BrBAMe], single crystal, belongs to the amino acid group, were grown by the slow evaporation solution growth technique at room temperature. The grown crystal had been subjected to single-crystal X-ray diffraction technique and cell parameters of the crystal were determined. The quantitative analysis on the crystal had been carried out using Fourier transform infrared (FTIR) and Fourier transform Raman (FT-Raman) spectral measurements. The molecular structures, vibrational wave numbers were calculated using DFT (B3LYP) method with 6-311++G(d,p) basis set. The formation of the hydrogen bond was investigated using NBO calculations. The calculated HOMO and LUMO energies show that charge transfer occur within the molecule. The dipole moment (μ) and polarizability (α0), anisotropy polarizability (Δα) and first order hyperpolarizability (β0) of the molecule have been reported.

Density functional theory and ab initio studies of vibrational spectra of 2-bis (2-chloroethyl) aminoperhydro-1,3,2-oxazaphosphorinane-2-oxide

The Fourier transform Raman (FTR) and Fourier transform infrared (FTIR) spectra of 2-bis (2-chloroethyl) aminoperhydro-1,3,2-oxazaphosphorinane-2-oxide were recorded in the regions 4000–100 cm− 1 and 4000–400 cm1, respectively, in the solid phase. Molecular electronic energy, geometrical structure, harmonic vibrational spectra, infrared intensities and Raman scattering activities, highest occupied molecular orbital, lowest unoccupied molecular orbital energy, energy gaps and thermodynamical properties such as zero-point vibrational energies, rotational constants, entropies and dipole moment were computed at the Hartree–Fock/6-31G(d,p) and three parameter hybrid functional Lee–Yang–Parr/6-31G(d,p) levels of theory. The vibrational studies were interpreted in terms of potential energy distribution. The results were compared with experimental values with the help of scaling procedures. The observed wave number in FTIR and FTR spectra was analysed and assigned to different normal modes of the molecule. Most of the modes have wave numbers in the expected range and are in good agreement with computed values.

Experimental and computational study on molecular structure and vibrational analysis of 4,5-Bis(hydroxymethyl)-2-methylpyridin-3-ol by normal coordinate treatment

The experimental and theoretical vibrational spectra of 4,5-Bis(hydroxymethyl)-2-methylpyridin-3-ol were investigated. The experimental FT-IR (450-4000cm(-1)) and FT-Raman spectra (100-3600cm(-1)) of the molecule in the solid phase were recorded. Theoretical vibrational frequencies and geometric parameters (bond lengths and bond angles) were calculated using ab initio Hartree Fock (HF) and density functional B3LYP method with 6-31G(d), 6-311++G(d,p) basis sets by Gaussian program, for the first time. The complete assignments were performed on the basis of the potential energy distribution (PED) of the vibrational modes, calculated with scaled quantum mechanical (SQM) method. The formation of the hydrogen bond was investigated using NBO calculations. The calculated HOMO and LUMO energies show that charge transfer occur within the molecule.

Normal co-ordinate analysis, molecular structural, non-linear optical, second order perturbation studies of Tizanidine by density functional theory

The spectroscopic techniques and semi-empirical molecular calculations have been utilized to analyze the drug Tizanidine (5CDIBTA). The solid phase Fourier Transform Infrared (FTIR) and Fourier Transform Raman (FTR) spectral analysis of 5CDIBTA is carried out along with density functional theory (DFT) calculations (B3LYP) with the 6-311++G(d,p) basis set. Detailed interpretation of the vibrational spectra of the compound has been made on the basis of the calculated potential energy distribution (PED). The individual atomic charges by NPA using B3LYP method is studied. A study on the Mulliken atomic charges, frontier molecular orbitals (HOMO-LUMO), molecular electrostatic potential (MEP) and thermodynamic properties were performed. The electric dipole moment (μ) and the first hyperpolarizability (α) values of the investigated molecule were also computed.

Vibrational spectroscopic studies of L-Alaninium oxalate

An organic crystal of L-Alaninium oxalate single crystal, belongs to the amino acid group, was grown by the slow evaporation solution growth technique at room temperature. The grown crystal had been subjected to single-crystal X-ray diffraction technique and cell parameters of the crystal were determined. The quantitative analysis on the crystal had been carried out using Fourier transform infrared (FTIR) and Fourier transform Raman (FTRaman) spectral measurements. The molecular structures, vibrational wave numbers were calculated using Density Functional Theory method. The calculated Thermodynamic properties were performed.