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Öğe EPR study of a gamma-irradiated (2-hydroxyethyl)triphenylphosphonium chloride single crystal(TAYLOR & FRANCIS LTD, 2011) Karakas, E.; Turkkan, E.; Dereli, O.; Sayin, U.; Tapramaz, R.In this study, gamma-irradiated single crystals of (2-hydroxyethyl)triphenylphosphonium chloride [CH(2)CH(2)OHP(C(6)H(5))(3)Cl] were investigated with electron paramagnetic resonance (EPR) spectroscopy at room temperature for different orientations in the magnetic field. The single crystals were irradiated with a (60)Co-gamma-ray source at 0.818 kGy/h for about 36 h. Taking the chemical structure and the experimental spectra of the irradiated single crystal of the title compound into consideration, a paramagnetic species was produced with the unpaired electron delocalized around (31)P and several (1)H nuclei. The anisotropic hyperfine values due to the (31)P nucleus, slightly anisotropic hyperfine values due to the (1)H nuclei and the g-tensor of the radical were measured from the spectra. Depending on the molecular structure and measured parameters, three possible radicals were modeled using the B3LYP/6-31+G(d) level of density-functional theory, and EPR parameters were calculated for modeled radicals using the B3LYP/TZVP method/basis set combination. The calculated hyperfine coupling constants were found to be in good agreement with the observed EPR parameters. The experimental and theoretically simulated spectra for each of the three crystallographic axes were well matched with one of the modeled radicals (discussed in the text). We thus identified the radical (C) over dotH(2)CH(2)P(C(6)H(5))(3)Cl as a paramagnetic species produced in a single crystal of the title compound in two magnetically distinct sites. The experimental g-factor and hyperfine coupling constants of the radical were found to be anisotropic, with the isotropic values g(iso)(=)2.0032, A(rad)(P2) = 118.6G, A(CH2)(H23) = 28.4G, A(CH2)(H24) = 4.2 G and A(CH2)(H40-41) = 18.5 G for site 1 and g(iso) = 2.0031, A(rad)(P2) = 118.9G, A(CH2)(H23) = 28.5 G A(CH2)(H24) = 4.3G and A(CH2)(H40-41) = 17.3 G for site 2.Öğe EPR study of gamma irradiated 2,5-di-tert-butyl-hydroquinone single crystals(PERGAMON-ELSEVIER SCIENCE LTD, 2011) Sayin, U.; Dereli, O.; Turkkan, E.; Yuksel, H.; Birey, M.gamma-irradiated single crystals of 2,5-di-tert-butyl-hydroquinone (DTBHQ) were investigated using the electron paramagnetic resonance (EPR) technique. The spectra of the crystals at different orientations in the magnetic field between temperatures of 120 and 450 K, were found to be temperature dependent. Taking into consideration the chemical structure and the experimental spectra of the irradiated single crystals of DTBHQ we assumed that one or more paramagnetic species were produced, each having an unpaired electron delocalized in the phenyl ring. Pursuant to this assumption, four possible radicals were modeled using the B3LYP/6-31+G(d) level of density-functional theory. EPR parameters were calculated for these modeled radicals using the B3LYP method and TZVP basis set. The calculated hyperfine-coupling constants were used as starting points for simulations. The experimental and simulated spectra for each of the three crystallographic axes were well matched for the modeled radical R4; we thus identified the hydroquinone anion radical as a paramagnetic species produced in DTBHQ. The experimental g-factor of the hydroquinone anion radical were found to be anisotropic with the average value g(iso)=2.0096. The hyperfine coupling constants of the H-alpha proton was found anisotropic with the average value (a(H7)(alpha))(iso) = 6.3 G and H-beta proton was found isotropic with the average value (a(H8)(beta))= 3.5 G. (C) 2010 Elsevier Ltd. All rights reserved.Öğe EPR study of gamma-irradiated diaminoglyoxime single crystals(ELSEVIER SCIENCE BV, 2011) Ates, L.; Dereli, O.; Turkkan, E.; Sayin, U.; Sevgi, F.; Tapramaz, R.; Birey, M.Gamma irradiated single crystals of diaminoglyoxime (DAG), were investigated with electron paramagnetic resonance (EPR) spectroscopy at room temperature and at different orientations in the magnetic field. Taking the chemical structure and the experimental spectra of the irradiated DAG single-crystal into consideration we assumed that iminoxy type paramagnetic species were produced where the unpaired electron is delocalized on N atoms. Depending on this assumption, an iminoxy radical was modeled and EPR parameters were calculated using the MP2/6-311++G(d,p)-level of theory and then the calculated hyperfine-coupling constants were used as initial guess for simulations. The experimental and simulated spectra for each of the three crystallographic axes well matched with the modeled radical. We thus identified an iminoxy radical as a paramagnetic species produced in DAG. The experimental g-factor and theoretically calculated hyperfine coupling constants of this radical were found to be anisotropic, with the average values g(iso) = 2.0150, a(N(4)) = -2.71 mT, a(N(3)) = 1.46 mT, a(N(9)) = 0.29 mT, a(N(12)) = 0.51 mT, a(H(10)) = -0.53 mT, a(H(11)) = -0.55 mT, a(H(13)) = -0.36 mT and a(H(14)) = -0.42 mT, respectively. (C) 2011 Elsevier B.V. All rights reserved.Öğe Experimental, theoretical calculations of the vibrational spectra and conformational analysis of 2,4-di-tert-butylphenol(PERGAMON-ELSEVIER SCIENCE LTD, 2012) Kalaichelvan, S.; Sundaraganesan, N.; Dereli, O.; Sayin, U.In the present work, we reported a combined experimental and theoretical study on conformational stability, molecular structure and vibrational spectra of 2,4-di-tert-butylphenol (2,4-DTBP). The FT-IR (400-4000 cm(-1)) and FT-Raman spectra (50-3500 cm(-1)) of 2,4-DTBP were recorded. The molecular geometry, harmonic vibrational frequencies and bonding features of 2,4-DTBP in the ground-state have been calculated by using the density functional BLYP/B3LYP methods. The energy calculated by time-dependent density functional theory (TD-DFT) result complements with the experimental findings. The calculated highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energies show that charge transfer occurs within the molecule. Finally the calculation results were compared with measured infrared and Raman spectra of the title compound which showed good agreement with observed spectra. (C) 2011 Elsevier B.V. All rights reserved.Öğe Molecular Structure and Vibrational Spectra of Alpha-Benzoinoxime by Density Functional Method(MAIK NAUKA/INTERPERIODICA/SPRINGER, 2014) Dereli, O.; Erdogdu, Y.; Gulluoglu, M. T.; Sundaraganesan, N.; Turkkan, E.; Sayin, U.; Ozmen, A.In the present study, an exhaustive conformational search of the Alpha-benzoinoxime has been performed. The FT-IR spectrum of this compound was recorded in the region 4000-400 cm(-1). The FT-Raman spectrum was also recorded in the region 3500-50 cm(-1). Vibrational frequences of the title compound were calculated by B3LYP method using 6-311++G(d, p) basis set. The calculated vibrational frequences were analysed and compared with experimental results.Öğe Radiation Damage Centers in Cholesteryl Heptanoate(POLISH ACAD SCIENCES INST PHYSICS, 2013) Sayin, U.; Can, C.; Turkkan, E.; Dereli, O.; Ozmen, A.; Yuksel, H.Cholesterol takes part significantly in many biological mechanisms and as important component for manufacture of bile acids, steroid hormones, and several fat-soluble vitamins. To determine magnetic properties of cholesteryl heptanoate (C34H58O2) which is an important cholesteryl ester in human life and new technology, the single crystals of cholesteryl heptanoate were grown by slow evaporation of concentrated ethyl acetate solution and the grown single crystals were irradiated at room temperature with Co-60 gamma ray. The radical produced by gamma irradiation has been investigated in the range of temperatures 123-330 K for different orientations of the crystal in a magnetic field by EPR. Radiation damage center was attributed to radical (C) over dotH(alpha)CH(2 beta). The g factor and hyperfine coupling constants have slight dependence on temperature and evident dependence on the orientation of the magnetic field. Determined g factor and hyperfine coupling constants for the radical (C) over dotH(alpha)CH(2 beta) were found to be anisotropic with the average values g(av) = 2.0036, (a(CH alpha))(av) = 14.52 G, (a(CH2 beta))(av) = 25.78 G.
