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    Probing the compound (E)-5-(diethylamino)-2-[(4-methylphenylimino)methyl]phenol mainly from the point of tautomerism in solvent media and the solid state by experimental and computational methods
    (Pergamon-Elsevier Science Ltd, 2011) Albayrak, Cigdem; Kastas, Gokhan; Odabasoglu, Mustafa; Frank, Rene
    In this study, the molecular structure and spectroscopic properties of (E)-5-(diethylamino)-2-[(4-methylphenylimino)methyl]phenol were characterized experimentally by X-ray diffraction, FT-IR and UV-vis spectroscopic techniques and computationally by DFT method. It is concluded on the basis of X-ray diffraction and FT-IR analyses that the title compound exists in enol form in the solid state. UV-vis spectra of the title compound were recorded in different organic solvents to investigate the dependence of tautomerism on solvent types. The tautomerism-solvent relation was also studied by computational methods to have more insight on structural properties. The geometry optimization of the title compound in gas phase was performed by using DFT (B3LYP) method with 6-311G(d,p) basis set. The geometry optimizations in solvent media were carried out at the same theory level by the polarizable continuum model (PCM). In the calculation of excitation energies, TD-DFT calculations were carried out in both gas and solution phases. The computational investigation of non-linear optical properties indicates that the title compound has a good second order nonlinear optical property. The thermodynamic properties were obtained in the range of 100-500 K. (C) 2011 Elsevier B.V. All rights reserved.
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    Single stranded helical chains of C-H•••π interactions further connected by halogen-halogen interactions of type I to construct supramolecular structure of (E)-5-(diethylamino)-2-[(4-iodophenylimino)methyl]phenol compound
    (Pergamon-Elsevier Science Ltd, 2012) Kastas, Gokhan; Albayrak, Cigdem; Odabasoglu, Mustafa; Frank, Rene
    In this study, (E)-5-(diethylamino)-2-[(4-iodophenylimino)methyl]phenol compound was investigated from the point of stacking interactions assembling the supramolecular network, conformational isomerism and tautomerism. For this purpose, X-ray diffraction, FT-IR and UV/Vis spectroscopic techniques were used, giving the following structural and spectroscopic properties of the compound: The title compound has two conformers (anti and eclipsed) in the crystal structure resulting from rotation about C-N single bond of ethyl group. Both conformers prefer enol form in the solid state, adopting E configuration about the C=N double bond. The supramolecular architecture of the compound is constructed by two non-covalent interactions as C-H center dot center dot center dot pi and halogen-halogen interactions. The repetition of C-H center dot center dot center dot pi interactions is resulted in a single-stranded helical structure. The helical structures are further connected by C-I center dot center dot center dot I-C interactions of Type I to construct the two dimensional supramolecular network defined as (6,3)-net in Wells nomenclature. The title compound adopts both enol and keto forms in EtOH (a polar and protic solvent) while enol form is preferred in the solid state. (C) 2012 Elsevier B.V. All rights reserved.
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    Spectroscopic, molecular structure characterizations and quantum chemical computational studies of (E)-5-(diethylamino)-2-[(2-fluorophenylimino)methyl]phenol
    (Elsevier, 2010) Albayrak, Cigdem; Frank, Rene
    The molecular structure and spectroscopic properties of (E)-5-(diethylamino)-2-[(2-fluorophenylimino)methyl]phenol were characterized by X-ray diffraction, IR and UV/Vis spectroscopy. These properties of title compound were also investigated from calculative point of view. Geometry optimization in gas phase was performed using DFT method with B3LYP applying 6-311G(d,p) basis set and geometry optimizations in solvent media were performed with the same level of theory by the polarizable continuum model (PCM). TD-DFT calculations starting from optimized geometry were carried out in both gas and solution phase to calculate excitation energies of title compound. In addition, while the non-linear optical properties were computed, thermodynamic properties were obtained at the optimized geometry with the same level of theory. The intramolecular proton transfer process from enol form to keto form was investigated using DFT method with B3LYP applying 6-311G(d,p) basis set. Transition state structure in EtOH was performed with the same level of theory by the polarizable continuum model (PCM). (C) 2010 Elsevier B.V. All rights reserved.
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    Spectroscopic, XRD, Hirshfeld surface and DFT approach (chemical activity, ECT, NBO, FFA, NLO, MEP, NPA& MPA) of (E)-4-bromo-2-[(4-bromophenylimino)methyl]-6-ethoxyphenol
    (Elsevier, 2019) Demircioglu, Zeynep; Kastas, Gokhan; Kastas, Cigdem Albayrak; Frank, Rene
    In the present work, the compound (E)-4-bromo-2-[(4-bromophenylimino)methyl]-6-ethoxyphenol was synthesized and characterized by spectroscopic (FT-IR and UV-Vis) and single crystal X-ray diffraction techniques. The intermolecular contacts in the compound was examined by Hirshfeld surfaces (HS) and fingerprint plots (FP) using the X-ray diffraction data. For other properties of interest, the geometry of the compound has been optimized by using the density functional theory (DFT) at B3LYP/6-311G (d,p) level. Molecular electrostatic potential (MEP), Fukui function (FF), nonlinear optical properties (NLO) and natural bond orbital (NBO) analyses have been performed and the global reactivity parameters have been obtained. The interactions between the title molecule and DNA bases (such as adenine, cytosine, guanine, and thymine) were investigated by using the ECT (electrophilicity-based charge transfer) method and Delta N (charge transfer). (C) 2019 Published by Elsevier B.V.
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    Survey of conformational isomerism in (E)-2-[(4-bromophenolimino)methyl]-5-(diethylamino)phenol compound from structural and thermochemical points of view
    (Pergamon-Elsevier Science Ltd, 2012) Albayrak, Cigdem; Kastas, Gokhan; Odabasoglu, Mustafa; Frank, Rene
    In this study, (E)-2[(4-bromophenylimino)methyl]-5-(diethylamino)phenol compound was investigated by mainly focusing on conformational isomerism. For this purpose, molecular structure and spectroscopic properties of the compound were experimentally characterized by X-ray diffraction, FT-IR and UV-Vis spectroscopic techniques, and computationally by DFT method. The X-ray diffraction analysis of the compound shows the formation of two conformers (anti and eclipsed) related to the ethyl groups of the compound. The two conformers are connected to each other by non-covalent C-H center dot center dot center dot Br and C-H center dot center dot center dot pi interactions. The combination of these interactions is resulted in fused R-2(2)(10) and R-2(4)(20) synthons which are responsible for the tape structure of crystal packing arrangement. The X-ray diffraction and FT-IR analyses also reveal the existence of enol form in the solid state. From thermochemical point of view, the computational investigation of isomerism includes three studies: the calculation of (a) the rate constants for transmission from anti or eclipsed conformations to transition state by using Eyring equation, (b) the activation energy needed for isomerism by using Arrhenius equation, (c) the equilibrium constant from anti conformer to eclipsed conformer by using the equation including the change in Gibbs free energy. The dependence of tautomerism on solvent types was studied on the basis of UV-Vis spectra recorded in different organic solvents. The results showed that the compound exists in enol form in all solvents except ethyl alcohol. (C) 2012 Elsevier B.V. All rights reserved.
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    The prototropic tautomerism and substituent effect through strong electron-withdrawing group in (E)-5-(diethylamino)-2-[(3-nitrophenylimino)methyl]phenol
    (Pergamon-Elsevier Science Ltd, 2013) Albayrak, Cigdem; Kastas, Gokhan; Odabasoglu, Mustafa; Frank, Rene
    The prototropic tautomerism in o-Hydroxy Schiff bases results in two forms called phenol-imine and keto-amine. The preference of a particular form by the compound changes in the solid and solvent media. The choice can also be regulated by a substituent with a different electron-donating or withdrawing group. In the present study, the above-mentioned factors are considered in the investigation of (E)-5-(diethylamino)-2-[(3-nitrophenylimino)methyl]phenol compound (an o-Hydroxy Schiff basis) by experimental (XRD, FT-IR and UV-vis) and computational (DFT and TD-DFT) methods. The results show that the title compound adopts only phenol-imine form in the solid and solvent media. This was attributed to the substituent effect through strong electron-withdrawing nitro group. (C) 2013 Elsevier B.V. All rights reserved.