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Results of studies on the effect of mechanochemical activation of ligand exchange processes inuranyl perchlorate-dimethylsulfoxide are presented. Spectroscopic data show that mechanical activation of the exchange process in this system results in the replacement of H 2 O in the first coordination sphere of uranyl UO 2 2+ by DMSO to form nanocrystals with a defined ligand sphere. Possible factors governing the noted features are considered.Introduction. The new technology of the 21st century, nanotechnology, relies on research on nanosystems (including nanoclusters). For example, cluster catalysts can create new directions for controlling the conversion and selectivity of catalytic reactions through the cluster size and its interaction with the matrix.Preparation methods, properties, and reactivity of nanoparticles and clusters of heavy-metal compounds (in particular, uranium) with several unique physical and chemical properties are currently of great interest. Uranium catalysts in the initial state may contain tri-, tetra-, penta-, or hexavalent metal [1][2][3]. This provides a greater variety of active centers than if lanthanide derivatives, which are as a rule trivalent, are used [1, 2]. On the other hand, tribochemical construction of small particles is important for the chemistry of materials science and the fabrication of materials with special properties.Changes occurring in a solid as a result of mechanical action are critically significant for understanding tribophysical and tribochemical processes. Changes in reactions involving reactive solids are proportional not to the amount of solid but to its surface area. The surface dimension is one of the principal reasons for an increase in overall activation. The increased reactivity of mechanically activated crystals can be explained by a lowering of the activation energy as a result of disrupting the bonding system on the solid surface. Such very small changes in the crystal structure can be followed by optical methods. This makes the study of their spectroscopic properties very important.Results. We used solid state substitution of some ligands by others in the first coordination sphere of uranyl to study the possibility of forming nanoclusters of uranyl perchlorate with various organic ligands.Herein vibrational spectroscopy is used to study formation of nanoclusters of hexavalent uranium perchlorates with organic ligands (dimethylsulfoxide, DMSO) upon mechanochemical activation of ligand exchange processes. These reagents were selected because, on one hand, hexavalent uranium (uranyl, UO 2 2+ ) is very stable in air and per-

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“…This agrees well with previous results [4] from an investigation of the coordination number of uranyl in solutions.…”

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confidence: 93%

Composition change of uranium perchlorates with organic ligands upon mechanochemical activation of exchange processes

Zazhogin

Komyak

et al. 2008

J Appl Spectrosc

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“…Crystallization of this species with alkali cations are known since the 19th century,3 and, since then, several crystalline alkali metal uranyl nitrates were reported containing sodium,4 potassium,5,6 rubidium,6,7 and cesium 6,8. Spectroscopic and luminescent properties of these compounds were studied in a number of works 9–14. Some alkali metal uranyl trinitrates such as the trigonal Rb(UO 2 )(NO 3 ) 3 have interesting optical properties such as strong molecular dichroism in visible light, owing to the orientation of the linear uranyl ion, [O=U=O] 2+ , parallel to the threefold axis.…”

Section: Introductionmentioning

confidence: 99%

Polymorphism in Alkali Metal Uranyl Nitrates: Synthesis and Crystal Structure of γ‐K(UO₂)(NO₃)₃

Jouffret

Krivovichev

Burns

2011

Zeitschrift anorg allge chemie

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Single crystals of γ-K(UO 2 )(NO 3 ) 3 were prepared from aqueous solutions by evaporation. The crystal structure [orthorhombic, Pbca (61), a = 9.2559(3) Å, b = 12.1753(3) Å, c = 15.8076(5) Å, V = 1781.41(9) Å 3 , Z = 8] was determined by direct methods and refined to R 1 = 0.0267 on the basis of 3657 unique observed reflections. The structure is composed of isolated anionic uranyl trinitrate units, [(UO 2 )(NO 3 ) 3 ] -, that are linked through eleven-coordinated K + cations.

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“…Reversibility of the reduction process is typical of solvents in which there is relatively little difference between the composition and structure of the starting solvates of U(VI) and the reduced U(V). For uranyl nitrate hexahydrate, studies have shown [5,6] that the coordination sphere of the uranyl in solvents of the DMSO type (solvents with a high donor number) is entirely filled with molecules of such a solvent, while the water and acido ligand molecules are located outside the coordination sphere. The same should also be expected for solvates of pentavalent uranium with solvents of this type, but such data at the moment is not sufficient to confidently assume that this hypothesis is correct.…”

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confidence: 99%

Complexation between variable-valency uranium and organic ligands in solutions, their photostability and spectral identification

2007

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We discuss possible directions for searching for prospective materials based on low-valency uranium (III-V) as detection media for hard electromagnetic radiation.We have studied the processes of formation of tetravalent and pentavalent uranium complexes from UO 2 (NO 3 ) 3 ⋅6H 2 O and UO 2 Cl 2 ⋅H 2 O in DMF and with addition of CCl 4 , including when the systems are exposed to radiation in the visible range (400-450 nm). In the first case (UO 2 (NO 3 ) 3 ⋅6H 2 O solutions in DMF), upon irradiation we observe stable complexes of pentavalent uranium, and when CCl 4 is added to the solution we observe complexes of tetravalent uranium. In the system UO 2 Cl 2 ⋅3H 2 O in DMF, we do not observe the appearance of new forms of uranium; but when CCl 4 is added, then complexes of tetravalent uranium are formed.Introduction. Rapid development of atomic projects at the end of the last century and the beginning of the current century has stimulated development of the technology for measuring ionizing radiation, including scintillation counters. Over a relatively short time, the major classes of scintillators were discovered and their widespread use began. These also include inorganic materials based on alkali halide compounds. In connection with creation of lasers and development of the technology for high-temperature synthesis of single crystals, it was found that the latter can play an important role as hard radiation detectors. In order to use them for such purposes, first of all problems must be solved concerning the spectroscopy of interconfiguration transitions of elements with a complete inner electron shell, where rare-earth ions have been advocated as such so far. The most promising class of such compounds has proven to be inorganic single crystals activated by Ce 3+ and Pr 3+ , which have good scintillation properties [1]. These ions are characterized by fast 5d-4f luminescence (with decay time on the order of tens of nanoseconds) in the violetultraviolet region of the spectrum (depending on the type of crystal matrix). We should point out that the emission properties of the Pr 3+ ion depend on the position of the d level in the bandgap and are sensitive to the strength and symmetry of the local crystal field. This often leads to the appearance of an additional channel for quenching of luminescence and consequently to limited use of Pr 3+ ions as activator ions. However, in a number of Pr 3+ matrices, intense interconfiguration luminescence is observed with decay times shorter than those typical of Ce 3+ in the same compounds. Such crystal compounds include Y 3 Al 5 O 12 :Pr, YAlO 3 :Pr, Y 2 SiO 5 :Pr, etc. This class of scintillators has been rather well studied so far. The prospects are not good for making new scintillation materials with density higher than 8.5 g/cm 3 and an effective charge higher than 72 within this class.Moreover, our preliminary estimates show that increasing the effective nuclear charge (for example, in U 4+ ions) should lead to a decrease in the energy gap between the 6d and 5f configura...

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Cited by 4 publications

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Composition change of uranium perchlorates with organic ligands upon mechanochemical activation of exchange processes

Composition change of uranium perchlorates with organic ligands upon mechanochemical activation of exchange processes

Polymorphism in Alkali Metal Uranyl Nitrates: Synthesis and Crystal Structure of γ‐K(UO₂)(NO₃)₃

Complexation between variable-valency uranium and organic ligands in solutions, their photostability and spectral identification

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Cited by 4 publications

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Composition change of uranium perchlorates with organic ligands upon mechanochemical activation of exchange processes

Composition change of uranium perchlorates with organic ligands upon mechanochemical activation of exchange processes

Polymorphism in Alkali Metal Uranyl Nitrates: Synthesis and Crystal Structure of γ‐K(UO2)(NO3)3

Complexation between variable-valency uranium and organic ligands in solutions, their photostability and spectral identification

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Polymorphism in Alkali Metal Uranyl Nitrates: Synthesis and Crystal Structure of γ‐K(UO₂)(NO₃)₃