| 1. |
- Abbasi, Alireza, et al.
(author)
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Ambidentate coordination of dimethyl sulfoxide in rhodium(III) complexes
- 2011
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In: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 40:5, s. 1111-1118
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Journal article (peer-reviewed)abstract
- The two dimethyl sulfoxide solvated rhodium(III) compounds, [Rh(dmso-kappa O)(5)(dmso-kappa S)](CF(3)SO(3))(3) (1 & 1* at 298 K and 100 K, respectively) and [Rh(dmso-kappa O)(3)(dmso-kappa S)(2)Cl](CF(3)SO(3))(2) (2), crystallize with orthorhombic unit cells in the space group Pna2(1) (No. 33), Z = 4. In the [Rh(dmso)(6)](3+) complex with slightly distorted octahedral coordination geometry, the Rh-O bond distance is significantly longer with O trans to S, 2.143(6) angstrom (1) and 2.100(6) angstrom (1*), than the mean Rh-O bond distance with O trans to O, 2.019 angstrom (1) and 2.043 angstrom (1*). In the [RhCl(dmso)(5)](3+) complex, the mean Rh-O bond distance with O trans to S, 2.083 angstrom, is slightly longer than that for O trans to Cl, 2.067(4) angstrom, which is consistent with the trans influence DMSO-kappa S > Cl > DMSO-kappa O of the opposite ligands. Raman and IR absorption spectra were recorded and analyzed and a complete assignment of the vibrational bands was achieved with support by force field calculations. An increase in the Rh-O stretching vibrational frequency corresponded to a decreasing trans-influence from the opposite ligand. The Rh-O force constants obtained were correlated with the Rh-O bond lengths, also including previously obtained values for other M(dmso)(6)(3+) complexes with trivalent metal ions. An almost linear correlation was obtained for the MO stretching force constants vs. the reciprocal square of the MO bond lengths. The results show that the metal ion-oxygen bonding of dimethyl sulfoxide ligands is electrostatically dominated in those complexes and that the stretching force constants provide a useful measure of the relative trans-influence of the opposite ligands in hexa-coordinated Rh(III)-complexes.
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| 2. |
- Matyskin, Artem, 1989, et al.
(author)
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Disordered Crystal Structure and Anomalously High Solubility of Radium Carbonate
- 2023
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In: Inorganic Chemistry. - 0020-1669 .- 1520-510X. ; 62:30, s. 12038-12049
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Journal article (peer-reviewed)abstract
- Radium-226 carbonate was synthesized from radium-barium sulfate (226Ra0.76Ba0.24SO4) at room temperature and characterized by X-ray powder diffraction (XRPD) and extended X-ray absorption fine structure (EXAFS) techniques. XRPD revealed that fractional crystallization occurred and that two phases were formed─the major Ra-rich phase, Ra(Ba)CO3, and a minor Ba-rich phase, Ba(Ra)CO3, crystallizing in the orthorhombic space group Pnma (no. 62) that is isostructural with witherite (BaCO3) but with slightly larger unit cell dimensions. Direct-space ab initio modeling shows that the carbonate oxygens in the major Ra(Ba)CO3 phase are highly disordered. The solubility of the synthesized major Ra(Ba)CO3 phase was studied from under- and oversaturation at 25.1 °C as a function of ionic strength using NaCl as the supporting electrolyte. It was found that the decimal logarithm of the solubility product of Ra(Ba)CO3 at zero ionic strength (log10 Ksp0) is −7.5(1) (2σ) (s = 0.05 g·L-1). This is significantly higher than the log10 Ksp0 of witherite of −8.56 (s = 0.01 g·L-1), supporting the disordered nature of the major Ra(Ba)CO3 phase. The limited co-precipitation of Ra2+ within witherite, the significantly higher solubility of pure RaCO3 compared to witherite, and thermodynamic modeling show that the results obtained in this work for the major Ra(Ba)CO3 phase are also applicable to pure RaCO3. The refinement of the EXAFS data reveals that radium is coordinated by nine oxygens in a broad bond distance distribution with a mean Ra-O bond distance of 2.885(3) Å (1σ). The Ra-O bond distance gives an ionic radius of Ra2+ in a 9-fold coordination of 1.545(6) Å (1σ).
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| 3. |
- Svengren, Henrik, et al.
(author)
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Direct Synthesis of Two Inorganic Catalysts on Carbon Fibres for the Electrocatalytic Oxidation of Water
- 2017
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In: Chemistry - A European Journal. - : Wiley. - 0947-6539 .- 1521-3765. ; 23:3, s. 568-575
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Journal article (peer-reviewed)abstract
- Two electrodes for anodic water oxidation made by direct synthesis of inorganic catalysts onto conductive carbon fibre sheets are evaluated. As catalysts two Co- and Sb-containing phases were tested, that is, Co3Sb4O6F6 and the new compound CoSbO4. The compounds express large differences in their morphology: CoSbO4 grows as thin needles whereas Co3Sb4O6F6 grows as larger facetted crystals. Despite the smaller surface area the latter compound shows a better catalytic performance. When the compound Co3Sb4O6F6 was used it gave a low increase of +0.028 mV h(-1) at an overpotential of eta = 472 mV after 10 h and a stability of +0.48 mV h(-1) at an overpotential of eta = 488 mV after 60 h. The leakages of Co and Sb were negligible and only <0.001 at% Co and approximately 0.02 at% Sb were detected in the electrolyte.
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| 4. |
- Torapava, Natallia, et al.
(author)
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A Coordination Chemistry Study of Solvated Thorium(IV) Ions in Two Oxygen-Donor Solvents
- 2011
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In: European Journal of Inorganic Chemistry. - : Wiley. - 1434-1948 .- 1099-0682. ; , s. 5273-5278
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Journal article (peer-reviewed)abstract
- The structures of the dimethyl sulfoxide (dmso) and N,N'-dimethylpropyleneurea (dmpu) solvated thorium(IV) ions have been studied in solution by extended X-ray absorption fine structure (EXAFS), and the structure of the solid oxonium bis[nonakis(O-dimethyl sulfoxide)]thorium(IV) trifluoromethanesulfonate dihydrate, (H3O)[Th((CH3)2SO)9]2(CF3SO3)9 center dot 2H2O (1) has been determined by single-crystal X-ray diffraction and EXAFS. Compound 1 was crystallized by evaporating a saturated dmso solution. It consists of two individual nonakis(O-dimethyl sulfoxide)thorium(IV) units, both of which have a tricapped trigonal prismatic configuration, as also found in nonakis(dimethyl sulfoxide)thorium(IV) perchlorate previously reported. Mean ThO bond lengths of 2.47 and 2.43 angstrom are found for the two structural units, respectively, for which the differences may be explained by differences in occupancy and temperature factors. The EXAFS data of 1 revealed mean ThO and SO bond lengths of 2.449(3) and 1.525(3) angstrom, respectively, and a ThOS bond angle of 135.2(5)inverted perpendicular to give a Th center dot center dot center dot S distance of 3.665(7) angstrom. In dmso solution, the mean ThO and SO bond lengths are 2.447(3) and 1.534(3) angstrom, respectively, the ThOS bond angle is 133.5(5)degrees, and there is a Th center dot center dot center dot C distance of 3.672(7) angstrom. The ThO bond-length distribution is somewhat asymmetric in both samples with Rmax values of 2.424 and 2.422 angstrom for 1 and solution, respectively. In dmpu solution, the ThO and CO bond lengths are 2.404(5) and 1.264(2) angstrom, respectively, and there is a ThOC angle of 157.1(5)degrees to give a Th center dot center dot center dot C distance of 3.594(7) angstrom. The observed ThO bond length indicates strongly that thorium(IV) is eight-coordinate in dmpu.
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| 5. |
- Torapava, Natallia, et al.
(author)
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Composition and Structure of Polynuclear Chromium(III) Hydroxo Complexes
- 2009
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In: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 48, s. 10383-10388
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Journal article (peer-reviewed)abstract
- The structures of the polynuclear hydrolysis complexes of chromium(III) formed in acidic and alkaline aqueous solution have been determined by means of extended X-ray absorption fine structure and large angle X-ray scattering. Chromium(III) is present as mononuclear hydrated ions below pH 3-4, with the upper limit depending on concentration, ionic strength, and temperature. Chromium(III) hydrolyzes in aqueous solution above this pH in concentrated aged solutions to mainly cationic tetrameric complexes containing both single and double hydroxo bridges between the chromium(III) ions. Above pH 5: the solubility of chromium(III) decreases sharply to form solid hydrated chromium(III) hydroxide. The solubility of chromium(III) increases sharply at elevated pH, and fairly concentrated solutions can be prepared in concentrated aqueous solutions of sodium hydroxide. According to the literature, mononuclear tetrahydroxochromate(III) complexes, Cr(OH)(4)(-) are formed in alkaline aqueous solution. However, this study shows polymeric chains of six-coordinated chromium(III) ions connected through double hydroxo bridges and with two terminal hydroxo groups giving an overall composition of (Cr(OH)(4))(n)(n-) This polymer is stable for a long time in solution at pH=15. However, at pH < 15, this polymer precipitates slowly with time, over months, to an amorphous phase with a structure around chromium similar to that in alpha-chromium(III) oxide hydroxide.
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| 6. |
- Torapava, Natallia, et al.
(author)
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Formation of a heteronuclear hydrolysis complex in the Th-IV-Fe-III system
- 2012
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In: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 41, s. 4451-4459
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Journal article (peer-reviewed)abstract
- The speciation in the mixed Th-IV-Fe-III system has been studied in aqueous solution in the pH range of 2.0-4.8. In the individual systems iron(III) and thorium(IV) hydrolyze easily and hydrolysis products precipitate at approximately pH >= 2.0 and 4.0, respectively, at the metal concentrations used in this study, 0.02-0.05 mol dm(-3). In the mixed Th-IV-Fe-III system precipitation of ferrihydrite takes place after months of storage at low pH values, 2.0 (six-line ferrihydrite) and 2.3 (two-line ferrihydrite), as identified by X-ray powder diffraction. In the pH range 2.9-4.5 no precipitation was observed after 24 months. Two thorium(IV)-iron(III) solutions with pH = 2.9, C-Th = 0.02 and 0.05 mol dm(-3) and C-Fe = 0.02 mol dm(-3), were studied by extended X-ray absorption fine structure, EXAFS, using the Fe K and Th L-3 edges, and a third solution with pH = 2.9 and C-Th = C-Fe = 0.40 mol dm(-3) by large angle X-ray scattering, LAXS, to determine the structure of the predominating species. A heteronuclear hydrolysis complex with the composition [Th2Fe2(mu(2)-OH)(8)(H2O)(12)](6+) is proposed to form in solution, with Th center dot center dot center dot Th, Th center dot center dot center dot Fe and Fe center dot center dot center dot Fe distances of 3.94(2) and 3.96(2), 3.41(3) and 3.43(2), 3.04(2) and 3.02(4) angstrom, as determined by EXAFS and LAXS, respectively.
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| 7. |
- Torapava, Natallia, et al.
(author)
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Hydration and Hydrolysis of Thorium(IV) in Aqueous Solution and the Structures of Two Crystalline Thorium(IV) Hydrates
- 2009
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In: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 48:24, s. 11712-11723
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Journal article (peer-reviewed)abstract
- Solid octaaqua(kappa O-2-perchlorato)thorium(IV) perchlorate hydrate, [Th(H2O)(8)(ClO4)](ClO4)(3)center dot H2O, 1, and aqua-oxonium hexaaquatris(kappa O-trifluoromethanesulfonato)thorium(IV) trisaquahexakis(kappa O-trifluoromethanesulfonato)-thorinate(IV), H5O2[Th(H2O)(6)(OSO2CF3)(3)][Th(H2O)(3)(OSO2CF3)(6)], 2, were crystallized from concentrated perchloric and trifluoromethanesulfonic acid solutions, respectively. 1 adopts a severely distorted tricapped trigonal prismatic configuration with an additional oxygen from the perchlorate ion at a longer distance. 2 consists of individual hexaaquatris(kappa O-trifluoromethanesulfonato)thorium(IV) and trisaquahexakis(kappa O-trifluoromethanesulfonato)thorinate(IV) ions and an aquaoxonium ion bridging these two ions through hydrogen bonding. The hydrated thorium(IV) ion is nine-coordinated in aqueous solution as determined by extended X-ray absorption fine structure (EXAFS) and large angle X-ray scattering (LAXS). The LAXS studies also showed a second hydration sphere of about 18 water molecules, and traces of a 3rd hydration sphere. Structural studies in aqueous solution of the hydrolysis products of thorium(IV) have identified three different types of hydrolysis species: a mu O-2-hydroxo dimer, [Th-2(OH)(2)(H2O)(12)](6+), a mu O-2-hydroxo tetramer, [Th-4(OH)(8)(H2O)(16)](8+), and a mu O-3-oxo hexamer, [Th6O8(H2O)(n)](8+). Detailed structures of these three hydrolysis species are given A compilation of reported solid state structures of actinoid(IV) compounds with oxygen donor ligands show a strong correlation between the An-O bond distance and the coordination number. The earlier reported U-O bond distance in the hydrated uranium(IV) ion in aqueous solution, confirmed in this study, is related to nine-coordination. The hydrated tri- and tetravalent actinoid ions in aqueous solution all seem to be nine-coordinated The trivalent ions show a significant difference in bond distance to prismatic and capping water molecules in assumed tricapped trigonal prismatic configuration, while the tetravalent ions seem to form more regular structures, probably because of higher polarization.
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| 8. |
- Torapava, Natallia
(author)
-
Hydration, solvation and hydrolysis of multicharged metal ions
- 2011
-
Doctoral thesis (other academic/artistic)abstract
- Structures of hydrated, solvated and hydrolyzed multicharged metal ions are determined by EXAFS and LAXS in solution, and by X-ray crystallography and EXAFS in the solid state. During hydrolysis, the nine-coordinate hydrated thorium(IV) ion is first transformed to a dimer, [Th₂(μ²-OH)₂(H₂O)₁₂]⁶⁺, then to a tetramer, [Th₄(μ²-OH)₈(H₂O)₁₆]⁸⁺, and finally to a hexamer, [Th₆(μ³-O₈)(H₂O)n]⁸⁺ with increasing pH and thorium(IV) concentration in an aqueous solution. Coordinated water looses the protons in two steps, first with the formation of the dimer and tetramer, and finally with the formation of the hexamer. Together thorium(IV) and iron(III) form a stable and highly soluble heteronuclear hydrolysis complex, [Th₂Fe₂(μ²-OH)₈(H₂O)₁₂]⁶⁺, in the pH range 2.9 - 4.8 and metal concentrations 0.02 – 0.4 mol·dm⁻³. In the same solutions at pH < 2.9 two- or six-line ferrihydrite precipitates with time, while thorium(IV) remains in solution. Palladium(II) and platinum(II) hydrolyze very slowly in acidic aqueous solution and after 25 years of storage tiny oxide-like particles are formed at pH = 0.7. The particle size has been estimated from the number of M···M distances in the formed particles and in the corresponding solid oxides from EXAFS studies. The palladium(II) and platinum(II) oxide particles grow along a or b axies and reach a size of 1 - 1.5 nm³. These results have been supported by SAXS studies. During hydrolysis, the six-coordinate hydrated chromium(III) ion is first transformed to a dimer, then to a tetramer, [Cr₄(μ²-OH)₂(μ-OH)₄(OH)n(H₂O)₁₂-n](6-n)+ with increasing pH from 0 to 3.7 at chromium concentration of ca. 1 mol·dm⁻³. At pH 15, soluble [Cr(μ²-OH)₂(OH)₂]nn-, n 3, complex is formed, which at pH < 15 slowly precipitates as an amorphous solid with a structure similar to α-CrOOH. Dimethylsulfoxide (DMSO) solvated thorium(IV) is nine-coordinate both in solution and solid state. N,N’-Dimethylpropyleneurea (DMPU) solvated thorium(IV) is eight-coordinate in solution. The lower coordination number is due to the space-demanding properties of the DMPU molecules upon coordination.
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| 9. |
- Torapava, Natallia, 1980, et al.
(author)
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Recrystallization of Ra-223 with barium sulfate
- 2014
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In: Journal of Radioanalytical and Nuclear Chemistry. - : Springer Science and Business Media LLC. - 0236-5731 .- 1588-2780. ; 301:2, s. 545-553
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Journal article (peer-reviewed)abstract
- In this work, the kinetics of barium sulfate recrystallization has been studied in acidic 0.01 mol dm -3 sodium sulfate solution using Ra-223 and Ba-133 tracers at very low total radium concentration, i. e. less than 10(-13) mol dm(-3). It was found that the system follows the homogeneous recrystallization model and that recrystallization rates, inferred by the decrease of Ra-223 and Ba-133 in the aqueous solution, are fast. Therefore, even at very low concentrations, below the solubility limit, radium will be retained by barium sulfate-a mineral present in the deep underground repository.
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| 10. |
- Torapava, Natallia, et al.
(author)
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Structures of polynuclear complexes of palladium(II) and platinum(II) formed by slow hydrolysis in acidic aqueous solution
- 2013
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In: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9234 .- 1477-9226. ; 42:21, s. 7755-7760
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Journal article (peer-reviewed)abstract
- The aqua ions of palladium(II) and platinum(II) undergo extremely slow hydrolysis in strongly acidic aqueous solution, resulting in polynuclear complexes. The size and structures of these species have been determined by EXAFS and small angle X-ray scattering, SAXS. For palladium(II), the EXAFS data show that the Pd-O and Pd center dot center dot center dot Pd distances are identical to those of crystalline palladium(II) oxide, but the intensities of the Pd center dot center dot center dot Pd distances in the Fourier transform at 3.04 and 3.42 angstrom are significantly lower compared to those of crystalline PdO. Furthermore, no Pd center dot center dot center dot Pd distances beyond 4 angstrom are observed. These observations strongly indicate that the polynuclear palladium(II) complexes are oxido- and hydroxido-bridged species with the same core structure as solid palladium(II) oxide. Based on the number of Pd center dot center dot center dot Pd distances, as derived from the EXAFS data, their size can be estimated to be approximately two unit cells, or ca. 1.0 nm(3). For platinum(II), EXAFS data of the polynuclear species formed in the slow hydrolysis process show Pt-O and Pt center dot center dot center dot Pt distances identical to those of amorphous platinum(II) oxide, precipitating from the solution studied. The Pt center dot center dot center dot Pt distances are somewhat different from those reported for crystalline platinum(II) oxide. The polynuclear platinum(II) complexes have a similar structure to the palladium ones, but they are somewhat larger, with an estimated diameter of 1.5-3.0 nm. It has not been possible to precipitate any of these species by ultracentrifugation. They are detectable by SAXS, indicating diameters between 0.7 and 2 nm, in excellent agreement with the EXAFS observations. The number of oxido- relative to hydroxido bridges will increase with increasing size of the complex. The charge of the complexes will remain about the same, +4, at growth, with approximate formulas [Pd10O4(OH)(8)(H2O)(12)](4+) and [Pt14O8(OH)(8)(H2O)(12)](4+) for complexes with a size of 2 and 3 unit cells of the corresponding solid metal oxide, respectively. Their high ionic charge in acidic aqueous solution will result in a stabilizing hydration shell.
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