Speciation, thermodynamics and structure of Np(<scp>v</scp>) oxalate complexes in aqueous solution

Maiwald, Martin; Trumm, Michael; Dardenne, Kathy; Rothe, Jörg; Skerencak-Frech, Andrej; Panak, Petra J.

doi:10.1039/d0dt02379e

Cited by 3 publications

(4 citation statements)

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“…In contrast, the C c distance in the malonate complexes are by 0.50–0.58 Å longer, indicating the formation of chelate rings involving one O atom of each COO – group. Furthermore, the C c distance in the NpO 2 (Mal) n 1–2 n complexes is in excellent agreement with the results for Np(V) oxalate complexes also displaying side-on coordination ( C c : 3.32 ± 0.06 Å) …”

Section: Resultssupporting

confidence: 86%

“…To investigate steric effects, the results for the Np(V) complexes of the present work are compared to recently published data for the complexation of Np(V) with oxalate (Ox 2– ) . A comparison of log β n ° (Θ) of oxalate, malonate, and succinate reveals a successive decrease of the complex stability with increasing C-backbone of the dicarboxylates.…”

Section: Resultssupporting

confidence: 81%

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Complexation of Np(V) with the Dicarboxylates, Malonate, and Succinate: Complex Stoichiometry, Thermodynamic Data, and Structural Information

et al. 2021

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The complexation of Np(V) with malonate and succinate is studied by different spectroscopic techniques, namely, attenuated total reflection Fourier transform infrared (ATR FT-IR) and extended X-ray absorption fine-structure (EXAFS) spectroscopy, as well as by quantum chemistry to determine the speciation, thermodynamic data, and structural information of the formed complexes. For complex stoichiometries and the thermodynamic functions (log β n °(Θ), ΔrH n °, ΔrS n °), near infrared absorption spectroscopy (vis/NIR) is applied. The complexation reactions are investigated as a function of the total concentration of malonate ([Mal2–]total) and succinate ([Succ2–]total), ionic strength [I m = 0.5–4.0 mol kg–1 Na+(Cl–/ClO4 –)], and temperature (Θ = 20–85 °C). Besides the solvated NpO2 + ion, the formation of two Np(V) species with the stoichiometry NpO2(L) n 1–2n (n = 1, 2, L = Mal2–, Succ2–) is observed. With increasing temperature, the molar fractions of both complex species increase and the temperature-dependent conditional stability constants log β n ′(Θ) at given ionic strengths are determined by the law of mass action. The log β n ′(Θ) are extrapolated to IUPAC reference-state conditions (I m = 0) according to the specific ion interaction theory (SIT), revealing thermodynamic log β n °(Θ) values. For all formed complexes, [NpO2(Mal)−: log β1 °(25 °C) = 3.36 ± 0.11, NpO2(Mal)2 3–: log β2 °(25 °C) = 3.95 ± 0.19, NpO2(Succ)−: log β1 °(25 °C) = 2.05 ± 0.45, NpO2(Succ)2 3–: log β2 °(25 °C) = 0.75 ± 1.22], an increase of the stability constants with increasing temperature was observed. This confirmed an endothermic complexation reaction. The temperature dependence of the log β n °(T) values is described by the integrated Van’t Hoff equation, and the standard reaction enthalpies and entropies for the complexation reactions are determined. Furthermore, the sum of the specific binary ion–ion interaction coefficients Δεn °(Θ) for the complexation reactions are obtained as a function of the t from the respective SIT modeling as a function of the temperature. In addition to the thermodynamic data, the structures of the complexes and the coordination modes of malonate and succinate are investigated using EXAFS spectroscopy, ATR-FT-IR spectroscopy, and quantum chemical calculations. The results show that in the case of malonate, six-membered chelate complexes are formed, whereas for succinate, seven-membered rings form. The latter ones are energetically unfavorable due to the limited space in the equatorial plane of the Np(V) ion (as NpO2 + cation).

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Section: Resultssupporting

confidence: 86%

Section: Resultssupporting

confidence: 81%

Complexation of Np(V) with the Dicarboxylates, Malonate, and Succinate: Complex Stoichiometry, Thermodynamic Data, and Structural Information

et al. 2021

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“…13 The vis-NIR spectrum of Np( v ) in wet RTIL shows a prominent peak at 976 nm, characteristic of the ion whereas for dry RTIL an additional peak at 1002 nm was seen along with the 971 peak, which can be attributed to its complexation with different ligands. 50–52 Dong et al , 41 have also observed few peaks in the Np( v ) vis-NIR spectrum in dry C 4 mim.NTf 2 and assigned their occurrence to the Np–hydroxo or carbonato complexes. 41 Though one would be tempted to conclude accordingly, our studies for CCI interactions between Np( v ) and U( vi ) in dry RTIL and wet RTIL contradict these peak assignments.…”

Section: Resultsmentioning

confidence: 95%

Effect of hydration of a room temperature ionic liquid on the cation–cation interaction of UO₂²⁺ and NpO₂⁺ ions

2023

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“…At the Priroda-optimized geometries, electronic structures were calculated in a tetrahydrofuran (THF) solution by using the ADF 2014 program . This approximation has proven to be reliable as re-optimizations have only a very slight effect on the structural parameters and molecular properties. − The default convergence criterion of 10 –6 au was used, and an integration parameter of 6.0 was applied. The solvation was taken into account using the Conductor-Like Screening Model, COSMO. , A dielectric constant of 7.58 was applied for THF, associated with the E surf -type of cavity.…”

Section: Computational Detailsmentioning

confidence: 99%

Theoretical Investigation of Catalytic Water Splitting by the Arene-Anchored Actinide Complexes

et al. 2022

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Actinide complexes, which could enable the electrocatalytic H2O reduction, are not well documented because of the fact that actinide-containing catalysts are precluded by extremely stable actinyl species. Herein, by using relativistic density functional theory calculations, the arene-anchored trivalent actinide complexes (Me,MeArO)3 ArAn (marked as [AnL]) with desirable electron transport between metal and ligand arene are investigated for H2 production. The metal center is changed from Ac to Pu. Electron-spin density calculations reveal a two-electron oxidative process (involving high-valent intermediates) for complexes [AnL] (An = P–Pu) along the catalytic pathway. The electrons are provided by both the actinide metal and the arene ring of ligand. This is comparable to the previously reported uranium catalyst (Ad,MeArO)3 mesU (Ad = adamantine and mes = mesitylene). From the thermodynamic and kinetic perspectives, [PaL] offers appreciably lower reaction energies for the overall catalytic cycle than other actinide complexes. Thus, the protactinium complex tends to be the most reactive for H2O reduction to produce H2 and has the advantage of its experimental accessibility.

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Speciation, thermodynamics and structure of Np(v) oxalate complexes in aqueous solution

Abstract: The speciation, thermodynamics and structure of the NpO2+ complexes with oxalate are studied by different spectroscopic techniques. Near infrared absorption spectroscopy (Vis/NIR) is used to investigate complexation reactions as a...

Cited by 3 publications

References 62 publications

Complexation of Np(V) with the Dicarboxylates, Malonate, and Succinate: Complex Stoichiometry, Thermodynamic Data, and Structural Information

Complexation of Np(V) with the Dicarboxylates, Malonate, and Succinate: Complex Stoichiometry, Thermodynamic Data, and Structural Information

Effect of hydration of a room temperature ionic liquid on the cation–cation interaction of UO₂²⁺ and NpO₂⁺ ions

Theoretical Investigation of Catalytic Water Splitting by the Arene-Anchored Actinide Complexes

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Speciation, thermodynamics and structure of Np(v) oxalate complexes in aqueous solution

Abstract: The speciation, thermodynamics and structure of the NpO2+ complexes with oxalate are studied by different spectroscopic techniques. Near infrared absorption spectroscopy (Vis/NIR) is used to investigate complexation reactions as a...

Cited by 3 publications

References 62 publications

Complexation of Np(V) with the Dicarboxylates, Malonate, and Succinate: Complex Stoichiometry, Thermodynamic Data, and Structural Information

Complexation of Np(V) with the Dicarboxylates, Malonate, and Succinate: Complex Stoichiometry, Thermodynamic Data, and Structural Information

Effect of hydration of a room temperature ionic liquid on the cation–cation interaction of UO22+ and NpO2+ ions

Theoretical Investigation of Catalytic Water Splitting by the Arene-Anchored Actinide Complexes

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Effect of hydration of a room temperature ionic liquid on the cation–cation interaction of UO₂²⁺ and NpO₂⁺ ions