Effect of Temperature on the Complexation of Uranium(VI) with Fluoride in Aqueous Solutions

Tian, Guoxin; Rao, Linfeng

doi:10.1021/ic900681x

Cited by 21 publications

(20 citation statements)

References 26 publications

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“…40 The absorption band of the uranyl complexes was broad in the visible range between 520 and 370 nm by extensive spectroscopy experiments studies on uranyl carbonate complexes 13,14,41,42 and some other inorganic ligands. 38,[43][44][45][46][47] The excitation energies above 370 nm of uranyl carbonate complexes in Table 4 are in accordance with the major characteristics observed from experiments discussed above. Just as the main assignments of excitations transitions shown in Table 4, transitions are essentially transferred from high occupied orbital to the low vacant orbital.…”

Section: Electronic Transitionssupporting

confidence: 81%

Electronic Structures of Uranyl(VI) Carbonate Complexes in the Aqueous Phase

Gu¹,

福州大学化学系²,

Lu³

et al. 2012

Acta Physico-Chimica Sinica

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A systematic study of series of non-hydrated and hydrated Cn/m uranyl carbonate complexes (n is number of carbonate ligands, and m is number of water molecules) in the aqueous phase was carried out using relativistic density functional theory. The conductor-like screening model was used to calculate solvent effects. The zeroth-order regular approximation was used to account for scalar relativistic effects and spin-orbit coupling relativistic effects. Time-dependent density functional theory with the inclusion of spin-orbit coupling relativistic effects was used to calculate electronic transitions using the statistically averaged orbital potentials. The results indicate that carbonate ligands play an important role in the geometric and electronic transition properties of the complex. The stability of the C3/0 carbonate complex in the aqueous phase may be attributed to the involvement of 5f components in the highest occupied bonding orbital. The addition of carbonate ligands caused a blue shift in the maximum wavelength and high intensity absorptions in the near visible region.

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Section: Electronic Transitionssupporting

confidence: 81%

Electronic Structures of Uranyl(VI) Carbonate Complexes in the Aqueous Phase

Gu¹,

福州大学化学系²,

Lu³

et al. 2012

Acta Physico-Chimica Sinica

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“…The bond dissociation energies (BDEs) in Tables and indicate that BDEs for actinide-fluorine bonds are generally greater than for carbon–fluorine bonds, and that the An–F bond strength decreases somewhat from An = U to Np to Pu. High actinide halide BDEs, BDE[An–X] (An = U, Np, Pu; X = F, Cl, Br), have been demonstrated by the ability of bare An + ions to abstract halogens from halogenated hydrocarbons. , A particular area of interest is complexes that comprise the actinyls, AnO 2 2+ , bound to one or more halide: AnO 2 X n (2‑ n )+ . ,− One motivation for studying such simple complexes is that the effective electron donation of halides to the actinide metal center affects the axial actinide-oxygen bonds, generally weakening them. − Uranyls, both U VI (unless otherwise specified the oxidation states hereafter are An VI ) and U V , have been shown to form various halide complexes in condensed and gas phases, , including as representative examples UO 2 X 3 – (X = F, Cl, Br, I), ,, UO 2 F n (2‑ n )+ ( n = 1–4), − UO 2 Br 4 2– , U V O 2 X (X = Cl, I), and UO 2 X 2 (X = Cl, Br) . It has been established that the complexation affinities of uranyl by halides decreases in the order F – > Cl – > Br – .…”

Section: Introductionmentioning

confidence: 99%

Halide Abstraction from Halogenated Acetate Ligands by Actinyls: A Competition between Bond Breaking and Bond Making

Dau

Gibson

2015

J. Phys. Chem. A

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Transfer of halogen atoms from halogenated acetate ligands, CX3CO2 (X = F, Cl, Br), to actinyls, AnO2(2+) (An = U, Np, Pu) is stimulated by collision-induced dissociation (CID) in a quadrupole ion trap. CID of [AnO2(CF3CO2)3](-) complexes results exclusively in F atom transfer, concomitant with elimination of CF2CO2, to produce [(CF3CO2)2AnO2F](-), [(CF3CO2)AnO2F2](-), and [AnO2F3](-). This contrasts with CID of transition metal fluoroacetates for which CO2-elimination to produce organometallics is an important pathway, a disparity that can be attributed to the differing bond dissociation energies (BDEs) of the created metal-carbon and metal-fluorine bonds. The dominant pathway for CID of [AnO2(CF3CO2)(CCl3CO2)(CBr3CO2)](-) is Br-atom transfer to produce [(CF3CO2)(CCl3CO2)AnO2Br](-). The preferential formation of bromides, despite that the BDEs of An-F bonds are substantially greater than those of An-Br bonds, is attributed to the offsetting effect of higher BDEs for C-F versus C-Br bonds. The results for the trihaloacetates are similar for uranyl, neptunyl and plutonyl, indicating that for all three the An-X bond dissociation energies are sufficiently high that X atom transfer is overwhelmingly dominant. CID of [UO2(CH2XCO2)2(CX3CO2)](-) (X = F, Cl, Br) resulted in F-transfer only from CH2XCO2, but Cl- and Br-transfer from both CH2XCO2 and CX3CO2, a manifestation of the characteristic increase in BDE[C-F] in CHx-nFn species as n increases; the overall thermochemistry determines the observed CID processes, providing clear distinctions between fluorides and chlorides/bromides. The results of this work reveal the propensity of the actinides to form strong bonds with halogens, and suggest that there is not a large variation in actinyl-halogen BDEs between uranyl, neptunyl, and plutonyl.

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“…As F − is a ligand with intermediate complexation strength toward trivalent actinides in aqueous solution, fluoride complexes of actinides are relevant for a nuclear waste repository in deep salt formations. Different techniques such as solvent extraction, ion exchange, potentiometric methods, − titration calorimetry, , and spectroscopy , have been applied to study the complexation of trivalent lanthanides and actinides with fluoride. These studies are mostly limited to ambient temperatures.…”

Section: Introductionmentioning

confidence: 99%

Complexation of Cm(III) with Fluoride in Aqueous Solution in the Temperature Range from 20 to 90 °C. A Joint TRLFS and Quantum Chemical Study

et al. 2010

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The formation of hydrated CmF2+ and CmF2+ species in aqueous solutions are studied in the temperature range of 20−90 °C at different fluoride concentrations and at constant ionic strength as well as at constant fluoride concentration and different ionic strengths by means of time-resolved laser fluorescence spectroscopy (TRLFS). The molar fractions of the Cm3+ aqua ion, CmF2+, and CmF2+ species are determined by peak deconvolution of the emission spectra. An increase of the mono- and difluoro complexes is observed with increasing fluoride concentration and/or increasing temperature. Using the specific ion interaction theory (SIT), the thermodynamic stability constants log K10 (CmF2+) and log K20 (CmF2+) as well as the values of Δε1 and Δε2 are determined as a function of temperature. The log K10 values increase from 3.56 ± 0.07 to 3.98 ± 0.06 and the log K20 values increase from 2.20 ± 0.84 to 3.34 ± 0.21 with increasing temperature from 20 to 90 °C. The value of Δε1 determined at 25 °C is in good agreement with literature data and shows a negligible temperature dependency in the studied temperature range. The value of Δε2 also shows only a moderate variation in the studied temperature range. The thermodynamic standard state data (ΔrHm0, ΔrSm0, ΔrGm0) are determined from the temperature dependence of the equilibrium constants at Im = 0 using the integrated Van’t Hoff equation. The fluorescence lifetime of the 6D′7/2(Cm3+) state is found to be constant at 63 ± 5 μs with increasing fluoride concentration. A model based on density functional theory (DFT) calculations is introduced to account for the additional quenching occurring through the near second sphere waters in the [Cm(H2O)8F]2+(H2O)18 complex.

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Effect of Temperature on the Complexation of Uranium(VI) with Fluoride in Aqueous Solutions

Cited by 21 publications

References 26 publications

Electronic Structures of Uranyl(VI) Carbonate Complexes in the Aqueous Phase

Electronic Structures of Uranyl(VI) Carbonate Complexes in the Aqueous Phase

Halide Abstraction from Halogenated Acetate Ligands by Actinyls: A Competition between Bond Breaking and Bond Making

Complexation of Cm(III) with Fluoride in Aqueous Solution in the Temperature Range from 20 to 90 °C. A Joint TRLFS and Quantum Chemical Study

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