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842 results on '"Ikeda, Yasuhisa"'

6. Electrochemical behavior of [UO2Cl4]2− in 1-ethyl-3-methylimidazolium based ionic liquids

Author

Ogura, Toshinari, Sasaki, Kotoe, Takao, Koichiro, Arai, Tsuyoshi, and Ikeda, Yasuhisa

Abstract

Abstract: In order to examine the chemical form of uranyl species in 1-ethyl-3-methylimidazolium (EMI) based ionic liquids, UV-visible absorption spectra of solutions prepared by dissolving [EMI]2[UO2Cl4] into a mixture of EMICl and EMIBF4 (50:50 mol%) were measured. As a result, it was confirmed that uranyl species in the mixture of EMICl and EMIBF4 existed as [UO2Cl4]2−. Cyclic voltammograms (CVs) of [UO2Cl4]2− in the mixture were measured at 25 °C using a Pt working electrode, a Pt wire counter electrode, and an Ag/Ag+ reference electrode (0.01 M AgNO3, 0.1 M tetrabutylammonium perchlorate in acetonitrile) in a glove box under an Ar atmosphere. Peaks corresponding to one redox couple were observed around −1.05 V (E pc) and −0.92 V (E pa) vs. ferrocene/ferrocenium ion (Fc/Fc+). The potential differences between two peaks (ΔE p) increased from 101 to 152 mV with an increase in the scan rate from 50 to 300 mV s−1, while the (E pc + E pa)/2 value was constant, −0.989 V vs. Fc/Fc+ regardless of the scan rate. Furthermore, the diffusion coefficient of [UO2Cl4]2− and the standard rate constant were estimated to be 3.7 × 10−8 cm2 s−1 and (2.7–2.8) × 10−4 cm s−1 at 25 °C. By using the diffusion coefficient and the standard rate constant, the simulation of CVs was performed based on the reaction, [UO2Cl4]2− + e− = [UO2Cl4]3−. The simulated CVs were found to be consistent with the experimental ones. From these results, it is concluded that [UO2Cl4]2− in the mixture of EMICl and EMIBF4 is reduced to [UO2Cl4]3− quasi-reversibly at −0.989 V vs. Fc/Fc+.

Published
2024
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7. Stability of pyrrolidone derivatives against γ-ray irradiation

Author

Nogami, Masanobu, Sugiyama, Yuichi, Kawasaki, Takeshi, Harada, Masayuki, Kawata, Yoshihisa, Morita, Yasuji, Kikuchi, Toshiaki, and Ikeda, Yasuhisa

Abstract

Abstract: To evaluate the stability of N-alkylated pyrrolidone derivatives (NRPs), which are supposed to be used as precipitants for U(VI) and Pu(IV, VI) species in HNO3 media, under irradiation environment, some candidate NRPs were irradiated by γ-ray. Irradiation to HNO3 solutions up to 6 mol dm−3 (= M) containing 2 M N-n-butyl-2-pyrrolidone (NBP), one of NRPs with lower hydrophobicity, has revealed that the residual ratios of NBP in the samples of HNO3 up to 3 M decreased identically and linearly. Approximately 20% of NBP was found to be degraded after the irradiation at 1 MGy. It was also found that the decrease in the precipitation ratio of UO22+ (P.R., %) was gentle and that the P.R. values were relatively in accordance with the residual ratios of NBP. On the other hand, the degradation of the samples irradiated in 6 M HNO3 was found more distinguished. It was proposed from the analyses of degraded compounds that the degradation of NBP in HNO3 by γ-ray irradiation started from the cleavage of the pyrrolidone ring by the addition of oxygen atom originating from HNO3, followed by the formation of chain compounds by the successive addition of oxygen, leading to the generation of oxalic acid and acetic acid. The stability of other NRPs in 3 M HNO3 was evaluated to be nearly identical with that of NBP except lower P.R. values of the samples containing NRPs with higher hydrophobicity irradiated at more than 0.5 MGy.

Published
2024
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34. Comparative study of uranyl(VI) and -(V) carbonato complexes in an aqueous solution

Author

Ikeda, Atsushi, Hennig, Christoph, Tsushima, Satoru, Takao, Koichiro, Ikeda, Yasuhisa, Scheinost, Andreas C., and Bernhard, Gert

Subjects
Aqueous solution reactions -- Analysis, Electrochemical analysis, Chemistry
Abstract

Electrochemical, complexation, and electronic properties of uranyl(VI) and (V) carbonato complexes in an aqueous N[a.sub.2]C[O.sub.3] solution was investigated to define the appropriate conditions for preparing pure uranyl(V) samples. Cyclic voltammetry using three different working electrodes of platinum, gold, and glassy carbon suggests that the electrochemical reaction of uranyl(VI) carbonate species proceeds quasi-reversibly.

Published
2007

35. Structural characterization and reactivity of U[O.sub.2](salophen)L and [[U[O.sub.2](salophen)].sub.2]: Dimerization of U[O.sub.2](salophen) fragments in noncoordinating solvents (salophen = N,N'-disalicylidene-o-phenylenediaminate, L = N,N-dimethylformamide, dimethyl sulfoxide)

Author

Takao, Koichiro and Ikeda, Yasuhisa

Subjects
Nuclear magnetic resonance spectroscopy -- Usage, Dimethyl sulfoxide -- Atomic properties, Dimethyl sulfoxide -- Structure, Chemistry
Abstract

Single crystal X-ray analysis and IR, [super 1]H NMR and ultraviolet (UV)-visible absorption spectroscopies are used to investigate the molecular structures of U[Osub.2](salophen)L (L = DMF, DMSO) and a uranyl-salophen complex without any unidentate ligands (L) in solid and solution. The reaction mechanisms including the L-exchange reaction in U[O.sub.2](salophen)L, the formation of [[U[O.sub.2](salophen)].sub.2] from U[O.sub.2](salophen)L, and the enantiomer exchange of [[U[O.sub.2](salophen)].sub.2] are proposed based on the kinetic information.

Published
2007

38. Electronic spectra of pure uranyl(V) complexes: Characteristic absorption bands due to a U(super v)O(sub 2)(super +) core in visible and near-infrared

Author

Mizuoka, Koichiro, Tsushima, Satoru, Hasegawa, Miki, Hoshi, Toshihiko, and Ikeda, Yasuhisa

Subjects
Near infrared spectroscopy -- Research, Absorption spectra -- Research, Chemistry
Abstract

The absorption spectra of three types of pure uranyl(V) complexes are measured to clarify the electronic spectral properties of uranyl(V) complexes. The results show that these uranyl(V) complexes have characteristic absorption bands in the visible-near infrared (NIR) region, which are useful for the deeper understanding of the spectroscopic properties of the actinyl species.

Published
2005

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