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    Synthesis, spectroscopic characterization and DFT calculations on N-(Phenylsulfonyl)-L-asparagine (NPLAS): A potential nonlinear optical material
    (Elsevier Gmbh, 2016) Gunay, Nergin; Tamer, Omer; Kuzalic, Dilek; Avci, Davut; Atalay, Yusuf
    The N-(Phenylsulfonyl)-L-asparagine (NPLAS), which is a potential nonlinear optical material, was synthesized and its geometric structure was optimized to obtain its geometric parameters, vibration frequencies and electronic structures at Hartree-Fock (HF) and B3LYP level of density functional theory (DFT) with 6-311 + +G(d,p) basis set, using Gaussian 09W program. The H-1 and C-13 nuclear magnetic resonance (NMR) chemical shifts of the title molecule were calculated by using the gauge independent atomic orbital (GIAO), continuous set of gauge transformations (CSGT) and individual gauges for atoms in molecules (IGAIM) methods and were also compared with experimental values. The electronic properties HOMO and LUMO energies were calculated and analyzed. Potential energy surface scan, natural population analysis (NPA) and Mulliken's atomic charges were also investigated using DFT and HF models. A detailed molecular picture and intermolecular interactions arising from hyperconjugative interactions and charge delocalization of the molecule were analyzed using natural bond orbital (NBO) analysis. (C) 2016 Elsevier GmbH. All rights reserved.
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    Theoretical Investigation of 6-(3,3,4,4,4-Pentafluoro-2-Hydroxy-1-Butenyl)-2,4-Dimethoxy-Pyrimidine Molecule
    (Springer Heidelberg, 2014) Pir, Hacer; Gunay, Nergin; Avci, Davut; Tamer, Omer; Tarcan, Erdogan; Atalay, Yusuf
    In this paper, we report a theoretical study on conformational, natural bond orbital (NBO) and nonlinear optical (NLO) analysis, molecular geometry, vibrational frequencies, H-1 and C-13 NMRchemical shifts values of the title molecule in the ground state calculated with the help of Density Functional Theory (DFT-B3LYP/6-311++G(d,p)) and Hartree-Fock (HF/6-311++G(d,p)) methods. In this study, conformational analysis has been calculated using Hartree-Fock (HF) at 6-31G level for the title molecule. The existence of intramolecular hydrogen bonding interactions, and various molecular parameters has been investigated by means of the natural bonding orbital (NBO) analysis. The optimized geometric parameters, vibrational frequencies, H-1 and C-13 NMR chemical shifts values are compared with experimental values of the investigated molecule. To understand this phenomenon in the context of molecular orbital picture, we examined the highest occupied molecule energy level (E-HOMO), the lowest unoccupied molecule energy level (E-LUMO), the energy difference (Delta E) between E-HOMO and E-LUMO, electronegativity (X), hardness (eta) and softness (S) calculated by HF/6-311++G(d,p) and B3LYP/6-311++G(d,p) levels. The calculated HOMO and LUMO energies show that the charge transfer occurs within the molecule. It has also been calculated thermodynamic parameters, molecular surfaces, Mulliken charges and atomic polar tensor-based charges of the investigated molecule. Finally, the calculated results were applied to simulate infrared and NMR spectra of the investigated molecules which showed good agreement with experimental ones.