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91.
The octahedral (FeO6)9? and tetrahedral (FeO4)5? clusters in yttrium gallium garnet (YGG): Fe3+ system are investigated based on the 252 × 252 complete energy matrices for d5 configuration ions in trigonal and tetragonal ligand fields, moreover, the EPR and optical spectra are made unified calculation. The results indicate that the defect structures around Fe3+ centres display expansion effects at different temperatures 4.2 and 295 K, and which are close to those in YIG garnet, respectively. Simultaneously, the defect structure parameters for Fe3+ centres in YGG are determined, and the relationship between the defect structure and the temperature has been discussed. 相似文献
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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 下载免费PDF全文
Yusuf Ceylan Keziban Usta Ahmet Kunduracioglu Ayhan Usta Bekir Cetinkaya 《Magnetic resonance in chemistry : MRC》2016,54(11):864-869
1‐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 1H NMR and 13C 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 72 h by using 60Co‐source with dose rate of 0.680 kGy. The EPR measurements were carried out in the temperature range of 200 K–450 K. 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 © 2016 John Wiley & Sons, Ltd. 相似文献
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The paramagnetic center of tetragonal symmetry formed by the Yb3+ ion in the KZnF3 crystal has been studied using methods of EPR, ENDOR and optical spectroscopy. The location of the impurity ion and the structural model of the complex differing from the model of the Yb3+ center in KMgF3 have been established. The empirical scheme of the energy levels of the Yb3+ ion has been found. The parameters of its interaction with the crystal electrostatic field and the hyperfine interaction with ligands of the nearest environment have been determined. The parameters of the crystal field were used for the analysis of the distortions of the crystal lattice in the vicinity of Yb3+. The parameters of the transferred hyperfine interaction have been calculated for the distances between Yb3+ and F− ions of the nearest environment obtained taking into account the found distortions. They are in good agreement with the experimental values. 相似文献
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Dr. Roberta Pievo Brigitta Angerstein Dr. Alistair J. Fielding Dr. Christian Koch Prof. Dr. Ivo Feussner Prof. Dr. Marina Bennati 《Chemphyschem》2013,14(18):4094-4101
Electron paramagnetic resonance (EPR) spectroscopy in combination with the rapid freeze‐quench (RFQ) technique is a well‐established method to trap and characterize intermediates in chemical or enzymatic reactions at the millisecond or even shorter time scales. The method is particularly powerful for mechanistic studies of enzymatic reactions when combined with high‐frequency EPR (ν≥90 GHz), which permits the identification of substrate or protein radical intermediates by their electronic g values. In this work, we describe a new custom‐designed micro‐mix rapid freeze‐quench apparatus, for which reagent volumes for biological samples as small as 20 μL are required. The apparatus was implemented with homemade sample collectors appropriate for 9, 34, and 94 GHz EPR capillaries (4, 2, and 0.87 mm outer diameter, respectively) and the performance was evaluated. We demonstrate the application potential of the RFQ apparatus by following the enzymatic reaction of PpoA, a fungal dioxygenase producing hydro(pero)xylated fatty acids. The larger spectral resolution at 94 GHz allows the discernment of structural changes in the EPR spectra, which are not detectable in the same samples at the standard 9 GHz frequency. 相似文献
98.
Benoît Driesschaert Philippe Levêque Bernard Gallez Jacqueline Marchand-Brynaert 《Tetrahedron letters》2013
A stable RGD-conjugated triarylmethyl (TAM) radical 3 has been synthesized in a straightforward three-step sequence. CT-03 ‘the Finland trityl’ which is a very popular contrast agent for electron paramagnetic resonance imaging has been covalently bound to the NH2-ending of a pentapeptide commonly used to target integrins and confers tissue selectivity. Moreover, this new TAM radical is stable and sensitive to molecular oxygen. 相似文献
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Elisabeth Siebert Marius Horch Yvonne Rippers Johannes Fritsch Stefan Frielingsdorf Oliver Lenz Francisco VelazquezEscobar Friedrich Siebert Lars Paasche Uwe Kuhlmann Friedhelm Lendzian Maria‐Andrea Mroginski Ingo Zebger Peter Hildebrandt 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2013,125(19):5267-5270