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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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    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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    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.
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    Experimental and theoretical research on -irradiated 7-methoxy-4-methylcoumarin powder through EPR and DFT methods
    (TAYLOR & FRANCIS LTD, 2018) Sarikaya, Ebru Karakas; Ates, Levent; Sayin, Ulku; Ozmen, Ayhan; Dereli, Omer
    In this paper, the effects of gamma irradiation on 7-Methoxy-4-methylcoumarin (7M4MC) molecule, an essential coumarin derivative, which has an inherent variety of biological activities, therapeutic properties and industrial usage were examined. For this purpose, the sample was irradiated with Co-60-gamma ray source for about 100kGy total doses. Theoretical calculations were performed using GAUSSIAN03 program for the possible radicals that were modeled from two stable conformations with lowest energies. In order to get well-resolved spectra and to determine the radical identity experimentally, EPR spectra of the irradiated 7M4MC sample were recorded at several spectrometer conditions. By considering the molecular structure and EPR spectra, alkyl-type radical was assumed to be formed by gamma irradiation. To support the estimations, simulations were done using theoretical EPR parameters as an initial value. The experimental spectra were well matched with the sum of simulated spectra obtained from two same type modeled radicals of two different conformations. As a result of experimental estimations and theoretical calculations, radiation-induced radicals were identified as two neutral alkyl radicals, originated from two stable conformations.
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    Molecular Structure and TD-DFT Study of the Xylene Isomers
    (GAZI UNIV, 2019) Kepceoglu, Abdullah; Gundogdu, Yasemin; Dereli, Omer; Kilic, Hamdi Sukur
    In this work, we have investigated the xylene isomers in concepts of vertical and adiabatic ionization energy parameters and molecular orbital (HOMO-1, HOMO/SOMO, LUMO, LUMO+1) energies of the neutrals and singly charged cation radicals. As a first step of the calculations, conformational analysis has been performed for all isomers using the semi-empirical method with PM3 core type Hamiltonian. Geometry optimization and frequency calculations were performed by using Density Functional Theory (DFT) with Becke, three-parameter, Lee-Yang-Parr (B3LYP) exchange-correlation functional and 6-311++G(d,p) basis sets. UV-Vis electronic spectra of the neutral xylene isomers were calculated by using the TD-DFT method with cam-B3LYP functional and 6-311++G(2d,2p) basis set.
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    Molecule and Radical Structures of Isobutyronitrile
    (GAZI UNIV, 2017) Dereli, Omer; Erdogdu, Yusuf; Ates, Levent; Karakas Sarikaya, Ebru; Ozturan, F. Pinar
    Molecule and radical structures of Isobutyronitrile were studied by DFT computations. Results of conformational analysis performed by combination of molecular mechanic and B3LYP/6-311++G(d, p) methods showed that isobutyronitrile inelastic molecule which has only one conformer. Using this structure, radical structure was investigated. Possible radicals were modelled and the experimental Electron Paramagnetic Resonance parameters were calculated. The calculated parameters obtained from B3LYP/TZVP computations were compared with the experimental counterparts which were taken from literature. Determined Molecule and Radical structures were given in this study.
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    Theoretical Calculations of Electron Paramagnetic Resonance Parameters of Succinimide Radical
    (AMER INST PHYSICS, 2018) Dereli, Omer; Ates, Levent; Erdogdu, Yusuf
    The analysis of the molecular structure and spectral properties of succinimide can be used as a reliable tool in understanding all interactions between this molecule with the other chemicals. For this reason, we first examined the conformational variety of succinimide in free state through an energy minimization calculations using the spartan 08 software. This preliminary calculation confirmed that free succinimide molecule has only one stable conformer at room temperature and the dipole moment and energy values of this conformer are 2.221 Debye and -360.779 Hartree, respectively. The optimized geometry of the conformer was then obtained at B3LYP/6-311++ G(d, p) level of theory by using the Gaussian 03 software. In the next step of the study, eleven radicals were formed from this one conformer of succinimide by removing an hydrogen atom or changing its location in the molecule. For each radical structure, the corresponding Electron Paramagnetic Resonance (EPR) parameters were calculated using the DFT/B3LYP method and TZVP basis set and then they were compared with the corresponding experimental values. The "g" value (EPR parameter) calculated in this study for the model radical (Rad 6) is 2.00388 and in good agreement with the corresponding experimental value (2,00339) previously reported in the literature for the radical form of succinimide.