Scandium Ions Research Articles

Elongation of Charge-Separation Lifetime of Zinc Quinoxalinoporphyrin-Gold Quinoxalinoporphyrin by Binding of Scandium Ion - Invited

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Defect interactions and ionic transport in scandia stabilized zirconia

Classical molecular dynamics simulation has been used to study ionic transport in scandia-stabilized zirconia, as well as scandia and yttria-co-doped zirconia, as a function of temperature and composition. The oxygen diffusion coefficient shows a peak at a composition of 6 mol% Sc(2)O(3). At 1125 K and higher temperatures, oxygen vacancies prefer to be second nearest neighbours to yttrium ions and first neighbours to scandium ions, because the defect interactions in scandia-stabilized zirconia are governed mainly by electrostatic effects. Oxygen migration between cation tetrahedra is impeded less effectively by Sc-Sc edges than by Y-Y edges. The formation of neutral dopant-anion vacancy clusters is favoured, in agreement with recent nuclear magnetic resonance observations.

Sc2(WO4)3 and Sc2(MoO4)3 and Their Solid Solutions: 45Sc, 17O, and 27Al MAS NMR Results at Ambient and High Temperature

The mobilities of trivalent ions are generally considered to be low in solid oxides and thus trivalent ionic conductors are rare. Sc2(WO4)3 and related compounds have been described as Sc3+ ionic conductors. However, there has not been conclusive experimental evidence whether Sc3+ is the major or the only mobile species. Here, we report 45Sc, 17O, and 27Al MAS NMR studies at ambient and high temperature of Sc2(WO4)3-type compounds including Sc2(WO4)3, Sc2(MoO4)3 (scandium tungstate and scandium molybdate), and their solid solutions, as well as aluminum-doped Sc2(WO4)3. 45Sc MAS NMR spectra at ambient temperature of the Sc2(WO4)3−Sc2(MoO4)3 binary are consistent with random mixing of W6+ and Mo6+ on tetrahedral sites. 17O spectra show that the details of the end-member short-range structure are preserved throughout this solid solution, indicating that lattice distortion is minimized by the close similarity of the radii of the hexavalent cations. Al3+ substitutes only into the octahedral sites. At high temperatures (600−700 °C), only the 17O high spectra show noticeable line shape changes, whereas 45Sc high-temperature spectra maintain a constant peak width and shift in position only, suggesting that the oxide anion may be a more mobile species but not excluding the possibility of a minor number of mobile scandium ions. 17O high-temperature NMR data also suggest that oxide ions bonded to molybdenum ions may be more mobile than those in tungstate groups.

Extraction of rare-earth, yttrium, and scandium perchlorates by podands bearing diphenylphosphorylacetamide terminal groups

Partition of trace amounts of metal (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y, and Sc) perchlorates was studied between aqueous HClO4 solutions and dichloroethane solutions of phosphorus podands bearing two Ph2P(O)CH2C(O)NH-terminal groups linked via di-and triethylene glycol spacers. The stoichiometry of extracted complexes was determined. The efficiency of metal ion recovery to the organic phase was studied as a function of aqueous HClO4 concentration and nature of the organic solvent. The compounds synthesized have higher metal extraction capacities in HClO4 solutions than (dibutylcarbamoyl)diphenylphoshine oxide. The utility of macroporous polymer sorbents impregnated by these podands for extracting and concentrating rare earth(III) and scandium(III) ions from aqueous perchlorate solutions was demonstrated.

Thermodynamic and kinetic properties of scandium (I) ion reacting with SCO in gas phase

Abstract Theoretical studies on the thermodynamic and kinetic properties of the reactions of scandium (I) ion with the sulfur-transfer reagent SCO via the C-O bond activation pathway have been carried out over the temperature range of 200-1200 K using the DFT/B3LYP method, general statistical thermodynamics, and Eyring transition state theory with Wigner correction. The relevant reactions include reaction 1 1Sc+ + SCO → 1IM1 → 1TS1 → 1IM2 (Step 1) → 1TS2 → 1IM3 → 1ScO+ + 1CS (Step 2), and reaction 2 3Sc+ + SCO → 3IM1 → CP → 1IM2 → 1TS2 → 1IM3 → 1ScO+ +1CS in which the spin multiplicity changes from the triplet state to the singlet state in the crossing region. It was concluded that the order of the equilibrium constants (K) and the reaction rate constants (k) are consistent with that of their corresponding exoergic energies, ΔE, and reaction barriers, respectively. Step 2 of reaction 1 is both thermodynamically and kinetically favored over the whole temperature range. Moreover, both Reaction 1 and reaction 2 are exothermic and spontaneous processes in which their entropy increases, and the magnitudes of their thermodynamic values all decrease with increasing temperature.

Two new types of oxyfluorotellurates(IV): ScTeO3F and InTeO3F

In the course of a general study of oxyfluorotellurates(IV), materials likely to exhibit interesting nonlinear optical properties, the crystal structures of the new phases scandium tellurium trioxide fluoride, ScTeO(3)F, and indium tellurium trioxide fluoride, InTeO(3)F, belonging to two different structural types and also differing from that of the recently published MTeO(3)F (M = Fe, Ga and Cr) series, have been determined. The ScTeO(3)F structure can be described as an intergrowth of two different layers of scandium octahedra connected via isolated TeO(3) groups. The scandium ions occupy two different sites with ..2 and 2.. site symmetry. The Te, F and O atoms are on general positions of the Pnna space group. The InTeO(3)F structure consists of zigzag sheets of InO(5)F octahedra. The In, Te, O and F atoms are all located on general positions of the P2(1)/a space group. TeO(3)F polyhedra are inserted between the zigzag sheets of InO(5)F octahedra and with them form double (InTeO(3)F)(n) layers. Therefore, InTeO(3)F is a true layer structure, unlike the previous types. In all these phases, the electronic lone pair of the Te(IV) atom is stereochemically active and a full O/F anionic ordering is observed.

Sc(OTf) 3-catalyzed carbomethoxylation of aliphatic amines with dimethyl carbonate (DMC): DMC activation by [formula omitted]-O(C [dbnd]O) coordination to Sc(III) and its relevance to catalysis

The role of metal center in the Sc(OTf) 3-catalyzed carbomethoxylation of aliphatic amines with DMC has been investigated. We have shown that the catalytic formation of carbamate ester is promoted by coordination of DMC to scandium(III) ion through the carbonyl oxygen atom. The ability of DMC to coordinate to Sc(III) has been proved by IR and NMR spectroscopy and fully demonstrated also by the isolation, for the first time, of a DMC–metal complex characterized as ( η 1 -O(C O)–DMC)Sc(OTf) 3. A relationship has been shown between the coordination mode of DMC to Sc(III) and the reactivity of coordinated organic carbonate: coordination of DMC to Sc(III) activates both carbonyl group and O–CH 3 moieties of the carbonic acid diester and enhances not only the carbomethoxylating but also the methylating activity of the ambident electrophile (DMC), as documented by the different selectivity exhibited by the catalyst in the aminolysis reaction of DMC with benzylamine and aniline, respectively.

Luminescence of La 3+ and Sc 3+ impurity centers in YAlO 3 single-crystalline films

The luminescence of La Y 3+ and Sc Y 3+ and Sc Al 3+ centers created by lanthanum and scandium ions at Y 3+ and Al 3+ cation sites of YAlO 3 perovskite lattice was investigated. The features of emission of excitons localized at the mentioned centers in YAlO 3:La and YAlO 3:Sc single-crystalline films were analyzed by means of time-resolved emission spectroscopy and luminescence decay kinetics measurements under excitation by synchrotron radiation at 9 and 300 K.

Extraction of scandium ions by 1-alkyl-3-methyl-2-pyrazolin-5-ones from perchlorate solutions

The extraction of perchloric acid and the two-phase partition of 1-alkyl-3-methyl-2-pyrazolin-5-ones (AMPs) in the system water-chloroform-perchloric acid are studied. These reagents can extract scandium cations from weak acid solutions in the presence of perchlorate ions. 1-Alkyl-3-methyl-2-pyrazolin-5-ones separate aqueous perchloric acid solutions into a pair of liquid phases. Scandium ions concentrate in the lower phase, which has a small volume.

Hyperfine structure of lithium-like scandium

The hyperfine structure of the ground state of the lithium-like scandium ion (Z = 21) is considered. The effects of electron-electron interaction are taken into account in the first order in 1/Z using the quantum electrodynamic perturbation theory and in higher orders using the method of configuration interaction in the Dirac-Fock-Sturm basis. One-loop radiative corrections are calculated in all orders in αZ with an effective local screening potential. The corrections for the finite nuclear size and the distribution of the magnetic moment over the nucleus have been refined.

Potassium magnesium and potassium cobalt molybdates: Synthesis and ion conductivity

Potassium magnesium and potassium cobalt molybdates of composition K2M2II (MoO4)3 (M = Mg, Co) and the products of their heterovalent doping by scandium(III) and vanadium(V) ions have been studied by impedance spectroscopy, powder X-ray diffraction, and electron microscopy. The compounds have high ion conductivity. Partial heterovalent substitutions of scandium for magnesium or vanadium for molybdenum additionally increases ion conductivity. The high conductivity of potassium magnesium and potassium cobalt molybdates allows us to consider them as promising solid electrolytes with potassium conductivity.

Formation of a Charge-Separated State of a Fullerene-Trinitrofluorenone Dyad by Complexation with Scandium Ion

A long-lived charge-separated state of fullerene-trinitrofluorenone linked dyad (C60- TNF) is formed in the presence of Sc(OTf)3 via intramolecular electron transfer from the singlet excited state of fullerene to TNF and binding of Sc3+ to the resulting TNF radical anion. The lifetime of the charge-separated state is determined as 23 ms in PhCN at 298 K.

Scandium Ion-accelerated Scavenging Reaction of Cumylperoxyl Radical by a Cyclic Nitroxyl Radical via Electron Transfer

Abstract A cyclic nitroxyl radical used as a spin probe efficiently scavenges cumylperoxyl radical in an aprotic medium via an electron-transfer process, which is significantly accelerated by the presence of scandium ion.

Fullerene acting as an electron donor in a donor–acceptor dyad to attain the long-lived charge-separated state by complexation with scandium ion

A long-lived charge-separated (CS) state of fullerene-trinitrofluorenone linked dyad in which fullerene acts as an electron donor is formed by photoinduced electron transfer from C60 to TNF in the presence of Sc(OTf)3; the CS lifetime is determined as 23 ms in PhCN at 298 K.

Local environment of scandium in aluminophosphate laser glasses: structural studies by solid state NMR spectroscopy

The first NMR study of a scandium oxide containing glass system is reported. The influence of scandium substitution for aluminium in the sodium aluminophosphate glass system (NaPO3)0.83–(Al2O3)0.17−x(Sc2O3)x (0 ≤ x ≤ 0.11) has been studied in detail by multinuclear high-resolution NMR experiments. Introduction of scandium into this glass system results in a systematic change in the aluminium speciation: as the substitutional parameter x is increased, aluminium is successively converted from six- to four-coordination. This result suggests that the scandium ions require more non-bridging oxygen atoms for coordination than aluminium in these glasses. 45Sc chemical shifts are consistent with isolated six-coordinated scandium species. 31P{45Sc} rotational echo adiabatic passage double resonance (REAPDOR) curves show a monotonic increase in slope with increasing x, indicating that the number of 31P–45Sc dipole–dipole couplings increases, consistent with a random spatial distribution of scandium. These results rule out the possibility of rare-earth clustering in these glasses. Both the 45Sc MAS-NMR spectra and 45Sc{31P} rotational echo double resonance (REDOR) data indicate that the scandium species adopt a constant, compositionally independent local environment dominated by phosphorus in the second coordination sphere.

Progress in stored ion beam experiments on atomic and molecular processes

Stored fast ion beams in atomic and molecular collision experiments are discussed with an emphasis on electron–ion interactions at low relative energies. Recent progress was obtained in electron collision spectroscopy using an electron-cooled stored ion beam and a separate electron target in the same storage ring; from a cryogenic photocathode, electron beams with internal temperatures of 5 to 10 K were produced. Results are presented for dielectronic recombination resonances, resolving the hyperfine structure of stored lithiumlike scandium ions and obtaining precise results for the fine structure splitting of these ions, and for ro-vibrational resonances in the recombination of electrons with hydrogen molecular ions, revealing sharp structures down to 2 meV. An overview of the cryogenic storage ring (CSR) project in Heidelberg is given.

Hydrothermal Synthesis and Crystal Structure of a New Inorganic/Organic Hybrid of Scandium Sulfate: (H2en)Sc2(SO4)4× (H2O)0.72.

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Hydrothermal synthesis and crystal structure of a new inorganic/organic hybrid of scandium sulfate: (H 2en)Sc 2(SO 4) 4·(H 2O) 0.72

The first organically templated layered structure of scandium sulfate, (H 2en)Sc 2(SO 4) 4·(H 2O) 0.72, (en=ethylenediamine) was synthesized by a hydrothermal method and characterized by single crystal X-ray diffraction. In the title compound, scandium ions are bridged by sulfate groups with a ratio of 1:2 into a 4 3 6 layer structure. These layers are parallel packed and separated from each other by ethylenediammonium dications and water molecules. The title compound crystallizes in the monoclinic space group P2/ c, with cell parameters a = 8.5966 ( 13 ) Å , b = 5.1068 ( 8 ) Å , c = 18.847 ( 3 ) Å , β = 91.210 ( 3 ) ° , V = 827.2 ( 2 ) Å 3 and Z = 2 . Refinement gave R 1[ I>2 σ( I)]=0.0354 and w R 2[ I>2 σ( I)]=0.0878. Thermogravimetric analysis indicates that this material is thermally stable to above 400 °C.

The hydration of the scandium(iii) ion in aqueous solution and crystalline hydrates studied by XAFS spectroscopy, large-angle X-ray scattering and crystallography

The structures of the hydrated scandium(III) ion and of the hydrated dimeric hydrolysis complex, [Sc2(mu-OH)2]4+, in acidic aqueous solutions have been characterized by X-ray absorption fine structure (XAFS) and large-angle X-ray scattering (LAXS) methods. Comparisons with crystalline reference compounds containing hydrated scandium(III) ions in well characterized six-, seven- and eight-coordinated polyhedra have been used to evaluate the coordination numbers and configurations in aqueous solution. In strongly acidic aqueous solution the structure of the hydrated scandium(III) ion is found to be similar to that of the eight-coordinated scandium(III) ion with distorted bicapped trigonal prismatic coordinating geometry in the crystalline [Sc(H2O)(8.0)](CF3SO3)3 compound. The EXAFS data reveal for the solution, as for the solid, a mean Sc-O bond distance of 2.17(1) Angstrom to six strongly bound prism water molecules, 2.32(4) Angstrom to one capping position, with possibly another capping position at about 2.5 Angstrom. The LAXS study supports this structural model and shows furthermore a second hydration sphere with approximately 12 water molecules at a mean Sc...O(II) distance of 4.27(3) Angstrom. In less acidic concentrated scandium(III) aqueous solutions, the dimeric hydrolysis product, [Sc2(mu-OH)2(H2O)10]4+, is the predominating species with seven-coordinated scandium(III) ions in a double hydroxo bridge and five terminal water molecules at a mean Sc-O bond distance of 2.145 Angstrom. Hexahydrated scandium(III) ions are found in the crystal structure of the double salt [Sc(H2O)6][Sc(CH3SO3)6], which crystallizes in the trigonal space group R3[combining macron] with Z = 6 and the unit cell dimensions a = 14.019(2) and c = 25.3805(5) Angstrom. The Sc-O distances in the two crystallographically unique, but nearly identical, [Sc(H2O)6]3+ entities (both with 3[combining macron] imposed crystallographic symmetry) are 2.085(6) and 2.086(5) Angstrom, while the mean Sc-O distance in the near octahedral [Sc(OSO2CH3)6]3- entities (with three-fold symmetry) is 2.078 Angstrom.

Highly Hydrated Cations: Deficiency, Mobility, and Coordination of Water in Crystalline Nonahydrated Scandium(III), Yttrium(III), and Lanthanoid(III) Trifluoromethanesulfonates

Trivalent lanthanide-like metal ions coordinate nine water oxygen atoms, which form a tricapped trigonal prism in a large number of crystalline hydrates. Water deficiency, randomly distributed over the capping positions, was found for the smallest metal ions in the isomorphous nonahydrated trifluoromethanesulfonates, [M(H2O)n](CF3SO3)3, in which M = Sc(III), Lu(III), Yb(III), Tm(III) or Er(III). The hydration number n increases (n = 8.0(1), 8.4(1), 8.7(1), 8.8(1) and 8.96(5), respectively) with increasing ionic size. Deuterium (2H) solid-state NMR spectroscopy revealed fast positional exchange between the coordinated capping and prism water molecules; this exchange started at temperatures higher than about 280 K for lutetium(III) and below 268 K for scandium(III). Similar positional exchange for the fully nonahydrated yttrium(III) and lanthanum(III) compounds started at higher temperatures, over about 330 and 360 K, respectively. An exchange mechanism is proposed that can exchange equatorial and capping water molecules within the restrictions of the crystal lattice, even for fully hydrated lanthanoid(III) ions. Phase transitions occurred for all the water-deficient compounds at approximately 185 K. The hydrated scandium(III) trifluoromethanesulfonate transforms reversibly (DeltaH degrees = -0.80(1) kJ mol(-1) on cooling) to a trigonal unit cell that is almost nine times larger, with the scandium ion surrounded by seven fully occupied and two partly occupied oxygen atom positions in a distorted capped trigonal prism. The hydrogen bonding to the trifluoromethanesulfonate anions stabilises the trigonal prism of water ligands, even for the crowded hydration sphere of the smallest metal ions in the series. Implications for the Lewis acid catalytic activity of the hydrated scandium(III) and lanthanoid(III) trifluoromethanesulfonates for organic syntheses performed in aqueous media are discussed.