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    (2-Hydroxyethyl)triphenylphosphonium chloride
    (WILEY-BLACKWELL, 2011) Ceylan, Umit; Tanak, Hasan; Turkkan, Ercan; Dereli, Omer; Buyukgungor, Orhan
    In the crystal structure of the title compound, C20H20OP+center dot Cl-, the cations and anions are linked by intermolecular CH center dot center dot center dot Cl and O-H center dot center dot center dot Cl hydrogen bonds into chains running parallel to the b axis. In the cation, the hydroxyethyl group is disordered over two orientations with site-occupancy factors of 0.554 (4) and 0.446 (4).
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    Anticancer, antimicrobial, spectral, voltammetric and DFT studies with Cu(II) complexes of 2-hydroxy-5-methoxyacetophenone thiosemicarbazone and its N(4)-substituted derivatives
    (ELSEVIER SCIENCE SA, 2017) Turkkan, Ercan; Sayin, Ulku; Erbilen, Nesibe; Pehlivanoglu, Suray; Erdogan, Gokce; Tasdemir, Halil Ugur; Saf, Ahmet Ozgur
    New copper complexes of 2-hydroxy-5-methoxyacetophenone thiosemicarbazone and its N(4)-substituted derivatives were synthesized and characterized by theoretical DFT studies and experimental UV-Vis, FT-IR, EPR spectral analysis, cyclic voltammetry, magnetic susceptibility and conductivity measurements. The DFT calculation results have been used to predict and interpret the experimental results. The geometric parameter G within the range of 7.61-7.86 for all complexes confirms the mononuclear nature of the complexes. The EPR, UV-Vis, DFT studies and obtained bonding parameters show that all the complexes have square planar geometry and their M-L bonds have strong ionic and some in-plane a-bond character. In addition, the experimental and DFT studies showed that HOMO and LUMO energy levels of the complexes may present good electron transporting properties. Also, the investigated Cu(II) complexes were tested for biological activity, proving both in vitro antibacterial and anticancer activity. The complexes exhibited antibacterial activity against Gram positive bacteria S. aureus while exhibiting no activities against gram negative bacteria E. toll and S. gallinarum. The f parameters obtained experimentally by EPR support the antimicrobial activity properties results of the complexes. The evaluations of potential anticancer activity of these complexes were carried out against highly metastatic MDA-MB-231 breast adenocarcinoma cell line by MTT assay. Our results suggest that all tested copper complexes have high cytotoxic effects with the range of 1.76-3.53 mu M IC50 values in vitro. These copper complexes could be considered as potential anticancer agents to counteract drug resistance of metastatic cancer cells. (C) 2016 Elsevier B.V. All rights reserved.
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    Effects of gamma irradiation on the single crystal ergosterol: An EPR study
    (ELSEVIER SCIENCE BV, 2012) Sayin, Ulku; Dereli, Omer; Turkkan, Ercan
    Single crystals of ergosterol were investigated by Electron Paramagnetic Resonance (EPR) technique, with gamma irradiation of the crystals at different orientations in the magnetic field between temperatures of 120 and 380 K, and the spectra were found to be slightly dependent on temperature. Because of the importance of ergosterol it is important to determine the irradiation effects on this molecule. Taking into consideration the chemical structure and the experimental spectra of the irradiated single crystal ergosterol, we found that two paramagnetic species which were labeled as radical A. (center dot)CH2(alpha)H(beta), and radical B-1 (CH alpha H beta H gamma H sigma)-C-center dot, were produced in the host crystal. The EPR parameters; spectroscopic splitting factor, g, and hyperfine coupling constant, a, were determined for each radical. (C) 2011 Elsevier B.V. All rights reserved.
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    An electron paramagnetic resonance and density-functional theory study on the methyl isotropic hyperfine coupling constants in gamma-irradiated 2,6-di-tert-butyl-4-methylphenol
    (TAYLOR & FRANCIS LTD, 2013) Turkkan, Ercan; Dereli, Omer; Sayin, Ulku; Tapramaz, Recep
    Single crystal of gammairradiated 2,6-di-tert-butyl-4-methylphenol (BHT) was investigated using an electron paramagnetic resonance (EPR) technique at different orientations in the magnetic field at room temperatures. Taking into consideration the chemical structure and the experimental spectra of the irradiated single crystal of BHT, we assumed that one phenoxyltype paramagnetic species was produced having an unpaired electron localized at the methyl fragment side of the phenyl ring. Depending on this assumption, one possible radical was modeled using the B3LYP/6-311+G(d) level of density-functional theory. EPR parameters were calculated for these modeled radical using the B3LYP/TZVP and B3LYP/EPR-III level. The averaged value of isotropic hydrogen hyperfine coupling constants of rotating methyl functional group of phenoxyl radical is calculated for the first time. Theoretically calculated values of the modeled radical are in reasonably good agreement with the experimental data determined from the spectra (differences in averaged coupling constant values smaller than 5%, and differences in isotropic g values fall into 1ppt).
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    EPR investigation of gamma irradiated single crystal guaifenesin: A combined experimental and computational study
    (PERGAMON-ELSEVIER SCIENCE LTD, 2016) Tasdemir, Halil Ugur; Sayin, Ulku; Turkkan, Ercan; Ozmen, Ayhan
    Gamma irradiated single crystal of Guaifenesin (Glyceryl Guaiacolate), an important expectorant drug, were investigated with Electron Paramagnetic Resonance (EPR) spectroscopy between 123 and 333 K temperature at different orientations in the magnetic field. Considering the chemical structure and the experimental spectra of the gamma irradiated single crystal of guaifenesin sample, we assumed that alkoxy or alkyl-type paramagnetic species may be produced by irradiation. Depending on this assumption, eight possible alkoxy and alkyl-type radicals were modeled and EPR parameters of these modeled radicals were calculated using the B3LYP/6-311+ +G(d,p)-level of density functional theory (DFT). Theoretically calculated values of alkyl-type modeled radical(R3) are in good agreement with experimentally determined EPR parameters of single crystal. Furthermore, simulation spectra which are obtained by using the thepretical initial values are well matched with the experimental spectra. It was determined that a stable C alpha H2 alpha C beta H beta C gamma H2 gamma (R3) alkyl radical was produced in the host crystal as a result of gamma irradiation. (C) 2015 Elsevier Ltd. All rights reserved.
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    EPR study of gamma-irradiated 2-Bromo-4 '-methoxyacetophenone single crystals
    (TAYLOR & FRANCIS LTD, 2016) Tasdemir, Halil Ugur; Turkkan, Ercan; Sayin, Ulku; Ozmen, Ayhan
    The gamma-irradiated single crystals of 2-Bromo-4'-methoxyacetophenone (2B4MA) were investigated using electron paramagnetic resonance (EPR) technique. Density-functional theory calculations were employed to investigate and identify the radicals that have been assumed to be formed upon irradiation of 2B4MA single crystals. The EPR spectra of 2B4MA were recorded at different orientations in the magnetic field at room temperature. Taking into account the chemical structure and experimental spectra of irradiated single crystal of 2B4MA, it was assumed that at least two different radicals were produced in the sample. Following this assumption, six possible radicals were modeled and EPR parameters were calculated by using the DFT, B3LYP/6-311+G(d), for the modeled radicals individually. The calculated hyperfine coupling constants and g-tensors were used as initial values for simulation studies. The three crystallographic axes on the simulated spectra were well matched with experimental spectra for the two modeled radicals. Thus, we identified the R1 type radical and R4 type radical as paramagnetic species produced in gamma-irradiated 2B4MA.
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    Experimental and DFT studies of (2-Hydroxyethyl) trihenylphosphoniumchloride
    (INT UNION CRYSTALLOGRAPHY, 2011) Ceylan, Umit; Tanak, Hasan; Turkkan, Ercan; Dereli, Omer; Buyukgungor, Orhan
    [Abstract not Available]
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    Experimental and Theoretical Electron Paramagnetic Resonance (EPR) Study on the Temperature-Dependent Structural Changes of Methylsulfanylmethane
    (MDPI, 2011) Tapramaz, Recep; Turkkan, Ercan; Dereli, Omer
    Methylsulfonylmethane (or dimethyl sulfone), a naturally produced and vitally important organosulfur compound in living organisms, was irradiated with gamma rays, and the produced radicals were investigated using electron paramagnetic resonance spectroscopy at different temperatures. The structure and behavior of the radical changed when the temperatures varied. The hyperfine splitting of the CH3 group was small, and the S-33 splitting was relatively high between 80 and -50 degrees C. When the temperature was between -50 and -160 degrees C, the S-33 splitting became small and the CH3 splitting was higher. However, the group kept rotating; therefore, only the isotropic splitting values were measured, and the g-values were anisotropic. When the temperature decreased below -180 degrees C, the CH3 group stopped rotating, and the hydrogen splitting values became nonequivalent due to an inhomogeneous electron distribution. The observed structures can be explained by referring to both the experimental and theoretically calculated values reported.