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    Studies on the synthesis, spectroscopic analysis and DFT calculations on (E)-4,6-dichloro-2-[(2-chlorophenylimino)methyl]-3methoxyphenol as a novel Schiff's base
    (Elsevier, 2016) Yildirim, Arzu Ozek; Yildirim, M. Hakki; Kastas, Cigdem Albayrak
    In this study, we report synthesis, single crystal X-ray diffraction, FT-IR and Uv-Vis. characterizations and computational investigations of the (E)-4,6-dichloro-2-[(2-chlorophenylimino)methyl]-3methoxyphenol. The tautomeric equilibrium between enol, keto and transition state (TS) forms of (E)-4,6-dichloro-2-[(2-chlorophenylimino)methyl]-3-methoxyphenol have been investigated by considering the presence of the compound in vacuum and various solvents. Experimental studies clearly reveal that the title compound has enol form in solid state and ethanol solution. In addition, the enol, keto and TS structures of the compound have been investigated computationally. Intramolecular proton transfer process on the O-H center dot center dot center dot N hydrogen bond and transition state structure during the transfer process have been studied by scan calculations for vacuum and solvent media. Moreover, the stabilization energies of the title compound were computed by using second-order perturbation theory to have insight on the intra- and intermolecular interactions, interaction among bonds, conjugative interactions. To find out most reactive sites of the title molecule, condensed Fukui functions have been calculated by means of natural population analysis. Nonlinear optical property calculations of the compound indicate that the compound can be used as a NLO material. (C) 2016 Elsevier B.V. All rights reserved.
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    Synthesis, crystal structure and computational studies of a new Schiff base compound: (E)-4-bromo-2-ethoxy-6-{[(2-methoxyphenyl)-imino]methyl}phenol
    (Int Union Crystallography, 2018) Yildirim, Arzu Ozek; Gulsu, Murat; Kastas, Cigdem Albayrak
    The title compound, C16H16BrNO3, which shows enol-imine tautomerism, crystallizes in the monoclinic P2(1)/ c space group. All non-H atoms of the molecule are nearly coplanar, with a maximum deviation of 0.274 ( 3) angstrom. In the crystal, molecules are held together by weak C-H center dot center dot center dot O, pi-pi and C-H center dot center dot center dot pi interactions. The E/Z isomerism and enol/keto tautomerism energy barriers of the compound have been calculated by relaxed potential energy surface scan calculations with DFT methods. To observe the changes in the aromatic ring, HOMA aromaticity indexes were calculated during the scan process. Total energy and HOMA change curves were obtained to visualize results of the scan calculations.
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    Öğe
    Synthesis, Spectroscopic, Conceptual DFT Characterization and Molecular Docking Studies of Two Versatile di-Bromobenzaldehyde Derived Compounds
    (Taylor & Francis Ltd, 2022) Yildirim, Arzu Ozek; Yildirim, Muhammet Hakki; Kastas, Cigdem Albayrak
    (E)-4,6-dibromo-2-[(2-chlorophenylimino)methyl]-3-methoxyphenol (I) and (E)-4,6-dibromo-2-[(2,5-difluorophenylimino)methyl]-3-methoxyphenol (II) Schiff base compounds were synthesized and characterized by using experimental XRD, FT-IR, UV-Vis. spectroscopic methods and computational methods. Geometry optimizations were done by using Gaussian type orbitals in Gaussian 09 W and Slater type orbitals in ADF2009 software. Spectroscopic studies show that the compounds prefer enol form in both solid and solvent. Scan calculations revealed that the reason for the enol form preference and the energy for prototropic tautomerism. From the biological activity estimations, it was determined that the compounds could be a Monoamine Oxidase Type B inhibitor, and comparative in-silico molecular docking studies with reverse docking of human monoamine oxidase type B protein were performed. Theoretical NLO calculations show that the second-order polarizability values of I and II were over 18 and 13 times that of the urea. Conceptual DFT studies were carried out to determine the reactivity descriptors of the molecules.
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    Öğe
    Synthesis, structural characterization and computational studies of (E)-4-bromo-2((3-chlorophenylimino)methyl)-6-ethoxyphenol
    (Elsevier, 2016) Yildirim, Arzu Ozek; Kastas, Cigdem Albayrak; Gulsu, Murat
    The present work reports on synthesis, single crystal X-ray diffraction, FT-IR, Uv-Vis., H-1 and C-13 NMR and theoretical calculations of the (E)-4-bromo-2-((3-chlorophenylimino)methyl)-6-ethoxyphenol compound. This study mainly focused on prototropic tautomerism and intramolecular proton transfer of (E)-4-bromo-2-((3-chlorophenylimino)methyl)-6-ethoxyphenol in solvent media and in solid state. Xray and FT-IR studies clearly reveals that the title compound exist in the enol form in solid state. Due to the dependence of prototropic tautomerism on solvent types, UV-Vis. spectra of the title compound were recorded in benzene, in chloroform and in ethanol. With the aid of theoretical calculations, important bands in the electronic spectrum were defined by means of frontier molecular orbitals. Intramolecular proton transfer process on the O-H center dot center dot center dot N hydrogen bond and transition state structure during the transfer process were investigated by scan calculations in the vacuum and in the different solvents. H-1 and C-13 NMR spectra were recorded in CDCl3 and detailed interpretation have been made on the basis of the theoretical calculations. Also, the stabilization energies of the title compound were computed by using second-order perturbation theory in order to investigate the intra- and intermolecular interactions, interaction among bonds, conjugative interactions. Nonlinear optical property calculations of the compound indicate that the material can be used as a NLO material. (C) 2015 Elsevier B.V. All rights reserved.