Browsing by Author "Sachan, AK"

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    Spectral investigation and theoretical study of zwitterionic and neutral forms of quinolinic acid
    Karabacak, M; Sinha, L; Prasad, O; Bilgili, S; Sachan, AK; Asiri, AM; Atac, A
    In this study, molecular structure and vibrational analysis of quinolinic acid (2,3-pyridinedicarboxylic acid), in zwitterionic and neutral forms, were presented using FT-IR, FT-Raman, NMR, UV experimental techniques and quantum chemical calculations FT-IR and FT-Raman spectra of 2,3-pyridinedicarboxylic acid (2,3-PDCA) in the solid phase were recorded in the region 4000-400 cm(-1) and 3500-0 cm(-1), respectively. The geometrical parameters and energies were obtained for zwitter and neutral forms by using density functional theory (DFT) at B3LYP/6-311++G(d,p) level of theory. 3D potential energy scan was performed by varying the selected dihedral angles using M06-2X and B3LYP functionals at 6-31G(d) level of theory and thus the most stable conformer of the title compound was determined. The most stable conformer was further optimized at higher level and vibrational wavenumbers were calculated. Theoretical vibrational assignment of 2,3-PDCA, using percentage potential energy distribution (PED) was done with MOLVIB program. C-13 and H-1 NMR spectra were recorded in DMSO. Chemical shifts were calculated at the same level of theory. The UV absorption spectra of the studied compound in ethanol and water were recorded in the range of 200-400 nm. The optimized geometric parameters were compared with experimental data. (C) 2015 Elsevier B.V. All rights reserved.
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    Experimental (FT-IR, FT-Raman, UV and NMR) and quantum chemical studies on molecular structure, spectroscopic analysis, NLO, NBO and reactivity descriptors of 3,5-Difluoroaniline
    Pathak, SK; Srivastava, R; Sachan, AK; Prasad, O; Sinha, L; Asiri, AM; Karabacak, M
    Comprehensive investigation of geometrical and electronic structure in ground as well as the first excited state of 3,5-Difluoroaniline (C6H5NF2) was carried out. The experimentally observed spectral data (FT-TR and FT-Raman) of the title compound was compared with the spectral data obtained by DFT/B3LYP method using 6-311++G(d,p) basis set. The molecular properties like dipole moment, polarizability, first static hyperpolarizability, molecular electrostatic potential surface (MEPs), and contour map were calculated to get a better insight of the properties of the title molecule. Natural bond orbital (NBO) analysis was applied to study stability of the molecule arising from charge delocalization. UV-Vis spectrum of the title compound was also recorded and the electronic properties, such as Frontier orbitals and band gap energies were measured by TD-DFT approach. Total and partial density of state (TDOS and PDOS) and also overlap population density of state (OPDOS) diagrams analysis were presented. Global and local reactivity descriptors were computed to predict reactivity and reactive sites on the molecule. H-1 and C-13 NMR spectra by using gauge including atomic orbital (GIAO) method of studied compound were compared with experimental data obtained. Moreover, the thermodynamic properties were evaluated. (C) 2014 Elsevier B.V. All rights reserved.
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    A combined experimental and theoretical investigation of 2-Thienylboronic acid: Conformational search, molecular structure, NBO, NLO and FT-IR, FT-Raman, NMR and UV spectral analysis
    Sachan, AK; Pathak, SK; Sinha, L; Prasad, O; Karabacak, M; Asiri, AM
    The solid state Fourier transform infrared (FT-IR) and Fourier transform Raman (FT-Raman) spectra of 2-Thienylboronic acid (2TBA), were recorded in the range of 4000-400 cm(-1) and 4000-100 cm(-1), respectively. DFT/B3LYP theory was used for the optimization of the ground state geometry and simulation of the infrared and Raman spectra of the title molecule. To determine lowest-energy molecular conformation of the studied molecule, the selected torsion angles were varied in steps of 10 degrees and complete 3D molecular energy profile was calculated. Among the four possible conformers (Trans-Trans, Cis-Cis, Trans-Cis and Cis-Trans), the most stable conformer of 2TBA is the Trans-Cis form. The vibrational wavenumbers and their assignments were carried out theoretically using the Gaussian09 set of quantum chemistry codes and the normal modes were calculated using MOLVIB program. Experimental FT-IR and FT-Raman spectra of the title compound were compared with the spectral data obtained by DFT/B3LYP method. Dipole moment, polarizability, first static hyperpolarizability and molecular electrostatic potential surface (MEPs) map have been calculated to get a better perception of the properties of the title molecule. Natural bond orbital (NBO) analysis was performed to study the stability of the molecule arising from charge delocalization. UV-Vis spectrum of the title molecule was also recorded (500-200 nm) in methanol and electronic properties such as frontier orbitals and energy gap were calculated by TD-DFT approach. The H-1 nuclear magnetic resonance (NMR) chemical shifts of the studied molecule were recorded in DMSO-d6 and calculated by Gauge-Including Atomic Orbital (GIAO) method. (C) 2014 Elsevier B.V. All rights reserved.
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    FT-IR, FT-Raman and UV spectroscopic investigation, electronic properties, electric moments, and NBO analysis of anethole using quantum chemical calculations
    Sinha, L; Prasad, O; Chand, S; Sachan, AK; Pathak, SK; Shukla, VK; Karabacak, M; Asiri, AM
    FT-IR and FT-Raman spectra of anethole (1-Methoxy-4-(1-propenyl)benzene), a flavoring agent of commercial value, have been recorded in the regions 4000-400 and 4000-100 cm(-1) respectively. The structure of the title molecule has been optimized and the structural parameters have been calculated by DFT/B3LYP method with 6-311++G(d,p) basis set. The fundamental vibrational wavenumbers as well as their intensities were calculated and a good agreement between observed and scaled calculated wavenumbers has been achieved. UV-Vis spectrum of the title compound was recorded in the region 200-500 nm and the electronic properties such as HOMO and LUMO energies and associated energy gap were calculated by Time dependent-density functional theory (TD-DFT) approach. Nonlinear optical (NLO) study divulges the nonlinear properties of the molecule. Stability of the title molecule arising from hyper-conjugative interactions and charge delocalization has been investigated using natural bond orbital (NBO) analysis. The theoretical results were found to be in coherence with the measured experimental data. (C) 2014 Elsevier B.V. All rights reserved.