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Öğe Determination of free radical on polycrystal of 4,4 '-bis(chloroacetyl)diphenylether: An ESR study(ELSEVIER SCIENCE BV, 2013) Ceylan, Yusuf; Usta, Ayhan; Usta, Keziban; Durmaz, Fatih; Coskun, Ahmet4,4'-Bis(chloroacetyl)diphenylether was synthesized and its polycrystal form was produced. This polycrystal sample was irradiated by gamma rays (Co-60) for 72 h. The ESR method was used to observe formation of free radical on the sample. ESR signal was not recorded from the non-irradiated sample, but the irradiated polycrystal sample exhibited complex ESR spectra. The measurements were carried out in the temperature range of 120-450 K. It was observed that the shape of the spectrum was dependent on the temperature. Two identical radicals were determined on the irradiated sample. Respectively, the spin density, hyperfine, and g values were found to be rho(Ha) = 0.53, rho(Hb) = 0.23, a(Cl) = 1.263 mT, a(Ha) = 1.486 mT, a(Hb) = 0.637 mT, and g(1) = 2.0115 for the Radical rho(Hx) = 0.22, rho(Hy) = 0.14, a(Cl) = 0.905 mT, a(Hx) = 0.615 mT, a(Hy) = 0.391 mT, and g(2) = 2.0383 for the Radical II. (C) 2013 Elsevier B.V. All rights reserved.Öğe An EPR Study On Cytosine Irradiated(WILEY, 2011) Usta, Ayhan; Vural, Hasibe Cingilli; Usta, Keziban; Aras, Erdal; Ceylan, Yusuf; Ozmen, AyhanIn this study, paramagnetic centers over the cytosine were formed by photolysis then these centers were investigated using EPR method. EPR signals were not recorded from non-irradiated the cytosine, but irradiated polycrystalline exhibited complex EPR spectra. For obtaining of cytosine polycrystalline, novel crystallization method was performed on powder cytosine. Effective crystallization conditions were achieved by adjustment of the concentration of the metal ions, chemical solutions, NaCl, KCl, glacial asetic acid, nitric oxide, percloric acid, glutamic acid, and pH of buffer. Cytosine (C4H5N2O) polycrystalline obtained were irradiated with Co-60 - rays at room temperature for 24 and 72 h. At the sample irradiated for 72 h, the paramagnetic centers were determined between 120 and 450 K by X-band EPR spectrometer. The spectra were found to be dependent slightly on temperature. Two cation radicals were determined in the structure and these were called Radicals I and II. The g and hyperfine constants were found to be a(H2a) = 61 G, a(N2) = 9.39 G, a(N1) = 7.15 G, and g(1) = 2.0026 for the Radical I; a(H3) = 10.57 G, a(H1) = 3 G, a(N3) = 6.72 G, a(N1) = 5.36 G for, and g(2) = 2.0034 the Radical II. Copyright (C) 2010 John Wiley & Sons, Ltd.Öğe Identification of radical structures on 1-pentamethylbenzyl-3-ethylimidazoliumsilver(I)bromide and 1,3-bis(pentamethylbenzyl)-4,5-dimethylbenzimidazoliumsilver(I)bromide exposed to gamma rays: an EPR study(WILEY, 2016) Ceylan, Yusuf; Usta, Keziban; Kunduracioglu, Ahmet; Usta, Ayhan; Cetinkaya, Bekir1-Pentamethylbenzyl-3-ethylimidazoliumsilver(I)bromide and 1,3-bis(pentamethylbenzyl)-4,5dimethylbenzimidazoliumsilver(I)bromide and their Ag+ complexes were synthesized and their polycrystal forms were produced by recrystallization in dichloromethane/Et2O solvent system. Structural determinations were carried out by H-1 NMR and C-13 NMR with a Varian 400 NMR system using tetramethylsilane as internal standard and CDCl3 as solvent. The disappearance of acidic N-heterocyclic carbene proton showed the formation of Ag(I) complexes. Also, elemental analyses were carried out. Electron paramagnetic resonance (EPR) measurements were performed to determine the formed radical structure on the samples irradiated at the room temperature for 72h by using Co-60-source with dose rate of 0.680kGy. The EPR measurements were carried out in the temperature range of 200K-450K. Identical radicals were determined on the irradiated compounds. It was observed that the shapes of the spectra of the samples were independent of the temperature but, the resonance line intensities changed linearly with the temperature. Also, it was detected that the free radical on the 1-pentamethylbenzyl-3-ethylimidazoliumsilver(I)bromide is not stable compared to that on the 1,3-bis(pentamethylbenzyl)-4,5dimethylbenzimidazoliumsilver(I)bromide. Copyright (c) 2016 John Wiley & Sons, Ltd.Öğe Investigation of irradiated 1H-Benzo[b] pyrrole by ESR, thermal methods and learning algorithm(TAYLOR & FRANCIS LTD, 2016) Algül, Gülay; Ceylan, Yusuf; Usta, Keziban; Aydoğmuş, Hacer Yumurtacı; Usta, Ayhan; Aşık, Biray1H-Benzo[ b] pyrrole samples were irradiated in the air with gamma source at 0.969 kGy per hour at room temperature for 24, 48 and 72 h. After irradiation, electron spin resonance, thermogravimetry analysis (TGA) and differential thermal analysis (DTA) measurements were immediately carried out on the irradiated and unirradiated samples. The ESR measurements were performed between 320 and 400 K. ESR spectra were recorded from the samples irradiated for 48 and 72 h. The obtained spectra were observed to be dependent on temperature. Two radical-type centres were detected on the sample. Detected radiation-induced radicals were attributed to R-+center dot NH and R=(center dot)CC2H2. The g-values and hyperfine constants were calculated by means of the experimental spectra. It was also determined from TGA spectrum that both the unirradiated and irradiated samples were decomposed at one step with the rising temperature. Moreover, a theoretical study was presented. Success of the machine learning methods was tested. It was found that bagging techniques, which are widely used in the machine learning literature, could optimise prediction accuracy noticeably.Öğe Screening of free radical formation in crystals of guanosine by ESR study(ELSEVIER SCIENCE BV, 2011) Usta, Ayhan; Vural, Hasibe Cingilli; Asik, Biray; Usta, KezibanIn this study, to obtain guanosine polycrystalline, novel crystallization method was performed on powder guanosine material. Effective crystallization conditions were achieved by adjustment of the concentration of the metal ions, chemical solutions, NaCl, KCl, glacial acetic acid, nitric oxide, perchloric acid, glutamic acid, and pH of buffer. Behaviors of the guanosine polycrystal samples exposed to high-energy values were investigated using ESR method. The polycrystal samples were exposed to gamma-rays for 48 and 72 h. ESR signals were not recorded from the non-irradiated sample and the sample irradiated for 48 h, but the polycrystalline sample irradiated for 72 h exhibited complex ESR spectra. ESR measurements were taken on the irradiated sample in temperature range from 300 to 450 K. On the basis of all these measurements dependence temperature, it can be said that the shape of the spectrum was to be dependent on temperature slightly. Hence, we assume that the radical structure occurred was resistance to high temperature. Two radicals were determined in the structure irradiated and these were called radical I and radical II. The g, hyperfine constants, and spin density were found to be rho = 0.96, a(NNH)(N) = 2.7 mT, a(NNH)(N) = 1.155 mT, a(N) = 0.35 ml and g(1) = 2.0093 for the radical 1; a(N) = 4.7 ml and g(2) = 2.0094 for the radical II. (C) 2011 Elsevier B.V. All rights reserved.
