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    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.
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    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.