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Now showing items 1 - 16 of 18

  • EPR of gamma irradiated single crystals of amphi-chloroglyoxime

    Sayin, Ulku   Yuksel, Huseyin   Yildirim, Bilge   Birey, Mehmet  

    The gamma-irradiated single crystals of amphi-chloroglyoxime were investigated by the electron paramagnetic resonance (EPR) between 123 and 400 K temperature. Paramagnetic species produced in the crystals were attributed to the R-HCCdotNOH radical and relevant spectra were found to be temperature independent. The g-factor and hyperfine coupling constants of the R-HCCdotNOH radical were found to be almost isotropic with the average values g=2.0009, a CN=31.89G, a HC=23.83G, a OH=9.49G and the spin densities rho CdotN=%50, rhoHCCdot=%50
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  • Self-assembly of a new building block of {BMo12O40} with excellent catalytic activity for methylene blue

    Findik, Mukerrem   Ucar, Asuman   Tolga Colak, Alper   Sahin, Onur   Bingol, Haluk   Sayin, Ulku   Kocak, Nuriye  

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  • Novel copper(II) and palladium(II) complexes with 4-aroyl-5-pyrazolone ligands:Synthesis and characterization

    Bagdatli, Emine   Yildirim, Fatih   Ulucay, Gorkem   Sayin, Ulku  

    Novel bidentate 4-aroyl-5-pyrazolone ligands were synthesized and reacted with copper(II) and palladium(II) salts in 1: 2 (metal: ligand) equimolar ratio leading to the formation of eight new coordination compounds. All synthesized compounds were characterized by FTIR, UVeVis, ESI-Mass, H-1 NMR, C-13-APT and also, in the case of the paramagnetic palladium(II) complexes, by ESR spectral studies. Additionally, elemental and thermogravimetric analyses (TG/DTG) were applied to all prepared complexes. These complexes are mononuclear and the copper(II) complexes have distorted square-planar geometry as determined by ESR. Spectral studies confirm the coordination of 4-aroyl-5-pyrazolone ligands through the carbonyl moieties to the metal. All the copper(II) complexes coordinated to the metal by enolization and the palladium(II) complexes showed 'Type B' coordination. The ligand which has 1-(4-methoxy) phenyl-substituted pyrazolone ring gave copper(II) complexes with a water molecule outside the coordination sphere. The proposed structures of the complexes agree well with the thermogravimetric decomposition results. (c) 2019 Elsevier B.V. All rights reserved.
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  • Effects of gamma irradiation on the single crystal ergosterol: An EPR study

    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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  • EPR study of gamma-irradiated 2-Bromo-4 '-methoxyacetophenone single crystals

    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 theoretical research on -irradiated 7-methoxy-4-methylcoumarin powder through EPR and DFT methods

    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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  • ESR analysis of natural and gamma irradiated coriander (Coriandrum sativum L.) seeds

    Sezer, M. Ozgur   Kaplan, Necati   Sayin, Ulku  

    Electron spin resonance ( ESR) is a powerful technique to detect radicals trapped in cellulosic food products and has been suggested as a useful method for identification of irradiated herbal foodstuffs. Coriander spice which has important medicinal properties was investigated using ESR spectroscopy. Radicals in natural and irradiated coriander samples were determined at room temperature. ESR spectra of natural sample were characterized by a single central signal with g =3D 2.0045 value and gamma irradiation produced satellite peaks attributed to cellulose- like radical which is used as a marker for detection of irradiated cellulosic plant products. The spectroscopic splitting values of radicals were determined. Dose dependency and stability of this center were analyzed by dose response and kinetic measurements. The reported results about activation energy, thermal life time and dose response relationship of the cellulose- like radical accurately prove that ESR can be used for identification of irradiated coriander spice seeds.
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  • Self-assembly of a new building block of {BMo12O40} with excellent catalytic activity for methylene blue

    Findik, Mukerrem   Ucar, Asuman   Colak, Alper Tolga   Sahin, Onur   Bingol, Haluk   Sayin, Ulku   Kocak, Nuriye  

    A novel organic-inorganic hybrid of 2,2'-bipyridyl (2,2'-bipy) linked covalently with the first inorganic framework based on boron-containing Keggin-type heteropolymolybdate anion [BMo12O40](5-) has been hydrothermally synthesized in aqueous solution. The crystal structure was fully characterized by elemental analyses, single crystal X-ray diffraction, Fourier-transform infrared spectrum (FT-IR), powder X-ray diffraction (XRD), Ultraviolet-visible spectroscopy (UV-Vis) and electron paramagnetic resonance (EPR) analysis. The catalytic performance of the synthesized catalyst was studied in degradation of methylene blue (MB) at ambient temperature. The catalyst exhibited excellent degradation against MB with a rate constant of 0.506/m, which was much higher than those by other polyoxometalate catalysts. Moreover, it was found to be easily separated from the reaction solution and recycled up to five times without significant loss of degradation activity. (C) 2019 Elsevier Ltd. 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

    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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  • Magnetic properties of single crystal alpha-benzoin oxime: An EPR study

    Sayin, Ulku   Dereli, Omer   Turkkan, Ercan   Ozmen, Ayhan  

    The electron paramagnetic resonance (EPR) spectra of gamma irradiated single crystals of alpha-benzoinoxime (ABO) have been examined between 120 and 440 K. Considering the dependence on temperature and the orientation of the spectra of single crystals in the magnetic field, we identified two different radicals formed in irradiated ABO single crystals. To theoretically determine the types of radicals, the most stable structure of ABO was obtained by molecular mechanic and B3LYP/6-31G(d,p) calculations. Four possible radicals were modeled and EPR parameters were calculated for the modeled radicals using the B3LYP method and the TZVP basis set. Calculated values of two modeled radicals were in strong agreement with experimental EPR parameters determined from the spectra. Additional simulated spectra of the modeled radicals, where calculated hyperfine coupling constants were used as starting points for simulations, were well matched with experimental spectra. (C) 2011 Elsevier Ltd. All rights reserved.
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  • ESR Characterization of Two Oxovanadium (IV) Schiff Base Complexes Derived from Tris(2-aminoethyl)amine

    Sahin, Mustafa   Kocak, Nuriye   Sayin, Ulku   Yilmaz, Mustafa  

    The compounds, C21H27N4O3(L-1) and C21H27N7(L-2), is a tripodal Schiff base that was obtained from the reaction of tris(2-aminoethyl)amine (tren) and furan-2-carbaldehyde and pyrole-2-carbaldehyde. The tripodal Schiff bases and their oxovanadium complexes have been characterized on the basis of the results of the elemental analysis, magnetic susceptibility measurements and spectroscopic studies FT-IR, H-1-NMR, UV-Vis, ESR, magnetic moment and thermal analysis (TGA). Job's method of continuous variation shows 3: 2 metal to ligand ratio.
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  • Determination of the irradiation effects on senna (Casia acutifolia) leaves by ESR technique and microbiological analysis

    Sezer, M. Ozgur   Ece, Emel   Uslu, Ali   Ozmen, Ayhan   Sayin, Ulku  

    In this study, the effects of irradiation on the Senna (Casia acutifolia) leaves exposed to gamma rays at various doses were investigated by means of Electron Spin Resonance (ESR) technique. Before irradiation a broad and asymmetric signal having g value of 2.0038 which was attributed to quinone radicals were observed. In the irradiated samples, a symmetric singlet signal with the g value of 2.0050 was detected and it was determined as radiation sensitive. According to isochronal annealing and fading studies it was shown that this signal was formed of short and long-lived two radicals. Because one of the components of the singlet signal in irradiated samples was quite stable at room temperature, so it was suggested to be used in irradiated food detection studies. It was revealed out by kinetic studies that the thermal responses of the singlet signals in natural and irradiated samples are different, thus it was emphasized that doing kinetic measurements for irradiated food detection was quite important, especially when the satellite signals could not be observed. Furthermore, by microbiological analysis, in order to investigate the effects of radiation on microorganisms in samples, microbial loads of irradiated samples at different doses were examined, and the lowest irradiation doses to inactive the microorganisms found in the natural sample were determined.
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  • The Importance of Pre-Annealing Treatment for ESR Dating of Mollusc Shells:A Key Study for Ismil in Konya Closed Basin/Turkey

    Ekici, Gamze   Sayin, Ulku   Aydin, Hulya   Isik, Mesut   Kapan, Sevinc   Demir, Ahmet   Engin, Birol   Delikan, Arif   Orhan, Hukmu   Biyik, Recep   Ozmen, Ayhan  

    In this study, Electron Spin Resonance (ESR) spectroscopy is used to determine the geological ages of fossil mollusc shells systematically collected from two different geological splitting at Ismil Location (37.72769 degrees N, 33.17781 degrees E) in eastern part of Konya. According to the assessment of obtained ESR ages, the importance of pre-annealing treatment emphasize in the case of g=3D2.0007 dating signal is overlapped with the other signals arisen from short lived radicals that cause the wrong age calculation. To overcome this problem, the samples are pre-annealed at 180 degrees C for 16 minutes and, in this case ESR ages are recalculated for g=3D1.9973 dating signal. Dose response curves are obtained using 1.9973 signals after pre-annealing treatments for each samples. ESR ages of samples are obtained in the range of 138 +/- 38 ka and 132 +/- 30 ka (Upper Pleistocene) according to the Early Uranium Uptake model and the results are in good agreement with the estimated ages from stratigraphic and paleontological correlation by geologists. Thus, it is suggested that especially in the case of g=3D2.0007 dating signal cannot been used due to superimposition case, the signal with 1.9973 g value can be used for dating after pre-annealing treatment. The results reports the first ESR ages on shells collected from Ismil Location and highlight the importance of pre-annealing treatment. This study is supported by TUBITAK 114Y237 research project.
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  • Magnetic properties of gamma irradiated single crystals of cholesteryl chloride: An EPR study

    Sayin, Ulku   Yuksel, Huseyin   Birey, Mehmet  

    The cholesteryl chloride compound has been irradiated with (60)Co-gamma ray at room temperature. The radical produced by gamma irradiation has been investigated in the range of temperatures 123-450 K for different orientations of the crystal in a magnetic field by electron paramagnetic resonance (EPR). Radiation damage center was attributed to radical CH(alpha)CH(2 beta)CH(2 gamma). The g factor and hyperfine coupling constants have slight dependency on temperature and evident dependency on the orientation of the magnetic field. Determined g factor and hyperfine coupling constants for the radical CH(alpha)CH(2 beta)CH(2 gamma), were found to be anisotropic with the average values g(av) = 2.003222,(a(CH alpha))(av) = 16.82G and (a(CH2 beta))(av) = 23.94G measured in all axes and (a(CH2 gamma))(av) = 8G, which was measured only in one axis. (C) 2011 Elsevier Ltd. All rights reserved.
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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

    Turkkan, Ercan   Sayin, Ulku   Erbilen, Nesibe   Pehlivanoglu, Suray   Erdogan, Gokce   Tasdemir, Halil Ugur   Saf, Ahmet Ozgur   Guler, Leyla   Akgemci, Emine Guler  

    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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  • EPR analysis of gamma irradiated single crystal cimetidine

    Sayin, Ulku  

    The magnetic properties of gamma irradiated single crystal cimetidine were investigated between temperatures of 123 K and 418 K and between microwave power of 0.01 mW and 150 mW by electron paramagnetic resonance. Magnetic field orientation in each of the three perpendicular axes, microwave power, and temperature dependence of the EPR spectra has led to more than one radical being produced by gamma irradiation in the host crystal. The distinctive radical was attributed to being a ring type radical; however, the other radicals could not be identified because of the superimposition. The EPR parameters of the ring type radical were determined to be: a(H-alpha)(av) = 2.42 mT, a(N-alpha)(av) = 0.62 mT, a(H-beta)(av) = 1.08 mT, a(H-gamma)(av) = 0.2 mT, a(N-beta)(av) = 0.3 mT, and (g)(av) = 2.0030, respectively. (C) 2012 Elsevier B.V. All rights reserved.
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