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Journal Articles

Conformation, hydration, and ligand exchange process of ruthenium nitrosyl complexes in aqueous solution; Free-energy calculations by a combination of molecular-orbital theories and different solvent models

Kido, Kentaro; Kaneko, Masashi

Journal of Computational Chemistry, 44(4), p.546 - 558, 2023/02

https://doi.org/10.1002/jcc.27021
 Times Cited Count：0 Percentile：0(Chemistry, Multidisciplinary)

Journal Articles

Cycloidal magnetic ordering in noncentrosymmetric EuIrGe$$_3$$

Matsumura, Takeshi*; Tsukakoshi, Mitsuru*; Ueda, Yoshihisa*; Higa, Nonoka*; Nakao, Akiko*; Kaneko, Koji; Kakihana, Masashi*; Hedo, Masato*; Nakama, Takao*; Onuki, Yoshichika*

Journal of the Physical Society of Japan, 91(7), p.073703_1 - 073703_5, 2022/07

https://doi.org/10.7566/JPSJ.91.073703
 Times Cited Count：1 Percentile：63.35(Physics, Multidisciplinary)

Journal Articles

Fully chelating N$$_{3}$$O$$_{2}$$-pentadentate planar ligands designed for the strongest and selective capture of uranium from seawater

Mizumachi, Takumi*; Sato, Minami*; Kaneko, Masashi; Takeyama, Tomoyuki*; Tsushima, Satoru*; Takao, Koichiro*

Inorganic Chemistry, 61(16), p.6175 - 6181, 2022/04

https://doi.org/10.1021/acs.inorgchem.2c00306
 Times Cited Count：1 Percentile：62.71(Chemistry, Inorganic & Nuclear)

Based on unique 5-fold equatorial coordination of UO$$_{2}$$$$^{2+}$$, water-compatible pentadentate planar ligands, H$$_{2}$$saldian and its derivatives, were designed as strong and selective capture of UO$$_{2}$$$$^{2+}$$ in seawater. In the simulated seawater condition (0.5 M NaCl + 2.3 mM HCO$$_{3}$$$$^{-}$$/CO$$_{3}$$$$^{2-}$$, pH 8), saldian$$^{2-}$$ shows the strongest complexation with UO$$_{2}$$$$^{2+}$$ to form UO$$_{2}$$(saldian) (log$$beta$$$$_{11}$$ = 28.05 $$pm$$ 0.07), which is more than 10 order of magnitude greater than amidoxime-based or -inspired ligand systems most commonly employed for U capture from seawater. Good selectivity for UO$$_{2}$$$$^{2+}$$ from other metal ions coexisting in seawater was also demonstrated.

Journal Articles

Complex formation of light and heavy lanthanides with DGA and DOODA, and its application to mutual separation in DGA-DOODA extraction system

Nomizu, Daiki; Sasaki, Yuji; Kaneko, Masashi; Matsumiya, Masahiko*; Katsuta, Shoichi*

Journal of Radioanalytical and Nuclear Chemistry, 331(3), p.1483 - 1493, 2022/03

https://doi.org/10.1007/s10967-022-08204-5

We studied the successive formation of water soluble DGA (diglycolamide) and DOODA (dioxaoctanediamide) for the mutual separation of Ln in this extraction system. TODGA (tetraoctyl-diglycolamide) and DOODA(C8) (tetraoctyl-dioxaoctanediamide) have the opposite trend to extract light and heavy Ln through Ln-patterns. Metal-complexes of two folding Ln ions with water-soluble DOODA and three folding with DGA are found and their observed formation constants are calculated. The suitable separation condition (aqueous phase: 30 mM DOODA(C2) in 1 M nitric acid, organic phase: 0.1 M TODGA in n-dodecane) of multi-stage extraction (10 $$times$$ 10) is conducted. From the present work, it is clear that La, Pr and Nd are mainly present in aqueous phase, instead Sm-Dy exist in the organic phase.

Journal Articles

Density functional study aiming to elucidate separation mechanisms of minor actinides and rare earths

Kaneko, Masashi

Nihon Genshiryoku Gakkai-Shi ATOMO$$Sigma$$, 64(1), p.30 - 34, 2022/01

https://doi.org/10.3327/jaesjb.64.1_30

Partitioning of minor actinides from rare earths is one of the most important techniques to develop group separation of high-level radioactive liquid waste. In this issue, the results of prediction of separation performance between minor actinides and rare earths observed in solvent extraction and the separation mechanism by means of using density functional theory are explained.

Journal Articles

Multi-stage extraction and separation of Ln and An using TODGA and DTBA or DTPA accompanying pH adjustment with lactic acid and ethylenediamine

Sasaki, Yuji; Kaneko, Masashi; Ban, Yasutoshi; Matsumiya, Masahiko*; Nakase, Masahiko*; Takeshita, Kenji*

Separation Science and Technology, 57(16), p.2543 - 2553, 2022/00

https://doi.org/10.1080/01496395.2022.2080707
 Times Cited Count：0 Percentile：0(Chemistry, Multidisciplinary)

The mutual separation of actinides (An) from lanthanides (Ln) using the masking agent of DTPA (diethylenetriamine-pentaacetic acid) or DTBA (diethylenetriamine-triacetic acid-bis(diethylacetamide)) in the aqueous phase through DGA extraction, referring TALSPEAK method, is focused. We investigate to obtain the same separation performance using commercially available DTPA on that using DTBA. In this work, we select lactic acid (LA) of pH buffer from 10 organic acids and ethylenediamine (ED) for the pH adjustment. Almost the same D and SF values are obtained among the conditions: TODGA-DTPA-LA-NaOH, TODGA-DTPA-LA-ED, and TODGA-DTBA-LA. The experimental results using batchwise multi-stage extractions show the average yields of Ln (La to Gd) and Am to be 3.73 and 98.1% in the aqueous phase using DGA-DTPA-LA-ED, to be 3.1 and 97.0% using DGA-DTPA-LA-NaOH, and to be 1.61 and 98.7% using DGA-DTBA-LA.

Journal Articles

Mutual separation of Ln and An using TODGA and DTBA with high organic acid concentrations

Sasaki, Yuji; Kaneko, Masashi; Matsumiya, Masahiko*; Nakase, Masahiko*; Takeshita, Kenji*

Solvent Extraction and Ion Exchange, 40(6), p.620 - 640, 2022/00

https://doi.org/10.1080/07366299.2021.2024650
 Times Cited Count：0 Percentile：0(Chemistry, Multidisciplinary)

Owing to the chemical behavior of trivalent lanthanide and actinide ions with similar ionic radii, realizing this separation is still challenging. All lanthanides, Am, and Cm can be extracted using diglycolamide (DGA), and relatively high An/Ln separation efficiencies have been obtained using diethylenetriamine-triacetic-bisamide (DTBA). To improve the previous results as well as the separation conditions, we used organic acids for pH adjustment. The advantages of this modification included low HNO$$_{3}$$, DTBA concentrations and pH stability owing to the addition of lactic acid. Under these modified conditions, the recovery rates observed were as follows: 97.1% for Nd with the co-existence of 1.59% Am in organic phase, and 98.4% for Am with the co-existence of 2.95% Nd in aqueous phase.

Journal Articles

Prediction of stability constants for novel chelates design in minor actinides partitioning over lanthanides using density functional theory calculation

Kaneko, Masashi; Sasaki, Yuji; Wada, Eriko*; Nakase, Masahiko*; Takeshita, Kenji*

Chemistry Letters, 50(10), p.1765 - 1769, 2021/10

https://doi.org/10.1246/cl.210402
 Times Cited Count：0 Percentile：0(Chemistry, Multidisciplinary)

Density functional theory calculation is applied to predict the stability constants for Eu$$^{3+}$$ and Am$$^{3+}$$ complexes in aqueous solution for molecular modelling of novel separation agents for minor actinides over lanthanides. Logarithm of experimental stability constants correlates with calculated complex formation enthalpies with high reproducibility (R$$^{2}$$ $$>$$ 0.98). Prediction of stability constants of novel chelates is demonstrated and indicates a potential availability of the derivatives of diethylenetriaminepentaacetic acid type chelate in acidic condition and enhancement of Am$$^{3+}$$ selectivity over Eu$$^{3+}$$.

Journal Articles

Density functional theory study on the $$^{193}$$Ir M$"o$ssbauer spectroscopic parameters of Vaska's complexes and their oxidative adducts

Kaneko, Masashi; Nakashima, Satoru*

Inorganic Chemistry, 60(17), p.12740 - 12752, 2021/09

https://doi.org/10.1021/acs.inorgchem.1c00239
 Times Cited Count：1 Percentile：0.01(Chemistry, Inorganic & Nuclear)

In the present study, density functional theory (DFT) calculation was applied to Vaska's complexes of formula ${it trans}$-[IrCl(CO)(PPh$$_{3}$$)$$_{2}$$], and their oxidative adducts with small molecules (YZ) including H$$_{2}$$, i.e., ${it trans}$-[IrCl(YZ)(CO))(PPh$$_{3}$$)$$_{2}$$], to successfully correlate the electronic states of the complexes with the corresponding $$^{193}$$Ir M$"o$ssbauer spectroscopic parameters. After confirming the reproducibility of the DFT methods for elucidating the equilibrium structures and $$^{193}$$Ir M$"o$ssbauer isomer shifts of the octahedral Ir complexes, the isomer shifts and quadrupole splitting values of Vaska's complexes and their oxidative adducts were calculated. A bond critical point analysis revealed that the tendency in the isomer shifts was correlated with the strength of the covalent interaction in the coordination bonds. In an electric field gradient (EFG) analysis of the oxidative adducts, the sign of the principal axis was found to be positive for the complex with YZ = Cl$$_{2}$$ and negative for the complex with YZ = H$$_{2}$$. This reversal of the sign of the EFG principal axis was caused by the difference in the electron density distribution for the coordination bonds between Ir and YZ, according to a density of states analysis.

Journal Articles

Density functional study on Am(III)/Eu(III) selectivity using crown ether type ligands

Fukasawa, Yuto*; Kaneko, Masashi; Nakashima, Satoru*

Journal of Radioanalytical and Nuclear Chemistry, 329(1), p.77 - 84, 2021/07

https://doi.org/10.1007/s10967-021-07685-0
 Times Cited Count：1 Percentile：30.57(Chemistry, Analytical)

Density functional theory calculations were applied to understand the selectivity between Am$$^{3+}$$ and Eu$$^{3+}$$ ions with the crown ethers type ligands. 18C6 is predicted to form the most stable complex with Eu$$^{3+}$$ and show the higher stability for Am$$^{3+}$$ over Eu$$^{3+}$$, being consistent with previously reported Am$$^{3+}$$/Eu$$^{3+}$$ selectivity. We modeled N- and S-donor complexes by using framework of 18C6 complex and analyzed the complexation Gibbs energies, indicating that 18C6 with N-donor atoms is suitable for both complexation and higher Am$$^{3+}$$ stability over Eu$$^{3+}$$ due to the stronger covalent interaction.

Journal Articles

Density functional modeling of Am$$^{3+}$$/Eu$$^{3+}$$ selectivity with diethylenetriaminepentaacetic acid and its bisamide chelates.

Kaneko, Masashi; Sasaki, Yuji; Matsumiya, Masahiko*; Nakase, Masahiko*; Takeshita, Kenji*

Journal of Nuclear Science and Technology, 58(5), p.515 - 526, 2021/05

https://doi.org/10.1080/00223131.2020.1842267
 Times Cited Count：2 Percentile：33.86(Nuclear Science & Technology)

Density-functional theory calculations were applied to molecular structure and complex formation reaction modelings of metal ion complexes with diethylenetriaminepentaacetic acid (DTPA) and its bisamide (DTPABA) chelates to understand the metal ions selectivity between Am$$^{3+}$$ and Eu$$^{3+}$$. The calculated complexes with DTPA and DTPABA chelates reproduced the coordination geometries of experimental crystal structures. Calculated Gibbs free energies of the complex formation reactions indicated that Am$$^{3+}$$ ion forms higher stable complexes with both chelates than Eu$$^{3+}$$ ion, being consistent with the experimental results. The higher Am$$^{3+}$$ selectivity over Eu$$^{3+}$$ was suggested to originate in the larger bond overlap between Am$$^{3+}$$ 5f-orbital and N 2s, 2p-orbital. This mean that the covalent contribution between metal ion and donor atoms differentiates the complex formation stabilities, leading to the Am$$^{3+}$$/Eu$$^{3+}$$ selectivity. We expect that this study contributes to systematize the origin of metal ions selectivity and to accelerate novel ligands exploration.

Journal Articles

Effect of oxygen-donor charge on adjacent nitrogen-donor interactions in Eu$$^{3+}$$ complexes of mixed N,O-donor ligands demonstrated on a 10-fold [Eu(TPAMEN)]$$^{3+}$$ chelate complex

Schnaars, K.; Kaneko, Masashi; Fujisawa, Kiyoshi*

Inorganic Chemistry, 60(4), p.2477 - 2491, 2021/02

https://doi.org/10.1021/acs.inorgchem.0c03405
 Times Cited Count：6 Percentile：65.73(Chemistry, Inorganic & Nuclear)

To reduce high-level radiotoxic waste generated by nuclear power plants, highly selective separation agents for minor actinides are mandatory. The mixed N,O-donor ligand ${it N,N,N',N'}$-tetrakis[(6-carboxypyridin-2-yl)methyl]ethylenediamine (H$$_{4}$$TPAEN) has shown good performance as a masking agent in Am$$^{3+}$$/Eu$$^{3+}$$ separation studies. In this work, we examine whether a decrease in O-donor basicity can promote the M$$^{3+}$$-N$$_{am}$$ interactions. Therefore, we replace the deprotonated "charged" carboxylic acid groups of TPAEN$$^{4-}$$ by neutral amide groups and introduce ${it N,N,N',N'}$-tetrakis[(6-${it N",N"}$-diethylcarbamoylpyridin-2-yl)methyl]ethylenediamine (TPAMEN) as a new ligand. TPAMEN was crystallized with Eu(OTf)$$_{3}$$ and Eu(NO$$_{3}$$)$$_{3}$$ 6H$$_{2}$$O to form positively charged 1:1 [Eu(TPAMEN)]$$^{3+}$$ complexes in the solid state. Alterations in the M-O/N bond distances are compared to [Eu(TPAEN)]$$^{-}$$ and investigated by DFT calculations to expose the differences in charge/energy density distributions at europium(III) and the donor functionalities of the TPAEN$$^{4-}$$ and TPAMEN. On the basis of estimations of the bond orders, atomic charges spin populations, and density of states in the Eu and potential Am and Cm complexes, the specific contributions of the donor-metal interaction are analyzed. The prediction of complex formation energy differences for the [M(TPAEN)]$$^{-}$$ and [M(TPAMEN)]$$^{3+}$$ (M$$^{3+}$$ = Eu$$^{3+}$$, Am$$^{3+}$$) complexes provide an outlook on the potential performance of TPAMEN in Am$$^{3+}$$/Eu$$^{3+}$$ separation.

Journal Articles

Magnetic skyrmion lattice in 4f electron magnet EuPtSi

Kaneko, Koji; Kakihana, Masashi*; Hedo, Masato*; Nakama, Takao*; Onuki, Yoshichika*

Hamon, 30(3), p.160 - 165, 2020/08

no abstracts in English

Journal Articles

Complexation and bonding studies on [Ru(NO)(H$$_{2}$$O)$$_{5}$$]$$^{3+}$$ with nitrate ions by using density functional theory calculation

Kato, Akane*; Kaneko, Masashi; Nakashima, Satoru*

RSC Advances (Internet), 10(41), p.24434 - 24443, 2020/06

https://doi.org/10.1039/D0RA05042C
 Times Cited Count：6 Percentile：43.96(Chemistry, Multidisciplinary)

Complexation reactions of ruthenium-nitrosyl complexes in HNO$$_{3}$$ solution were investigated by density functional theory (DFT) calculations in order to predict the stability of Ru species in high-level radioactive liquid waste (HLLW) solution. Equilibrium structure of [Ru(NO)(NO$$_{3}$$)$$_{3}$$(H$$_{2}$$O)$$_{2}$$] obtained by DFT calculations reproduced the experimental Ru-ligands bond lengths and IR frequencies reported previously. Comparison of the Gibbs energies among the geometrical isomers revealed that the complexation reactions of the ruthenium-nitrosyl complexes with NO$$_{3}$$$$^{-}$$ proceed via the NO$$_{3}$$$$^{-}$$ coordination to the equatorial plane toward the Ru-NO axis. We also estimated Gibbs energy differences on the stepwise complexation reactions to succeed in reproducing the fraction of Ru-NO species in 6 M HNO$$_{3}$$ solution, such as in HLLW, by considering the association energy between the Ru-NO species and the substituting ligands. Electron density analyses of the complexes indicated that the strength of the Ru-ligands coordination bonds depends on the stability of the Ru species and the Ru complex without NO$$_{3}$$$$^{-}$$ at the axial position is more stable than that wit NO$$_{3}$$$$^{-}$$, which might attribute to the difference in the trans influence between H$$_{2}$$O and NO$$_{3}$$$$^{-}$$. Finally, we demonstrated the complexation kinetics in the reactions $$x = 1 rightarrow x = 2$$. The present study is expected to enable us to model the precise complexation reactions of platinum-group metals in HNO$$_{3}$$ solution.

Journal Articles

Magnetic skyrmion lattice in 4$$f$$ electron magnet EuPtSi

Kaneko, Koji; Kakihana, Masashi*; Hedo, Masato*; Nakama, Takao*; Onuki, Yoshichika*

Kotai Butsuri, 54(12), p.757 - 766, 2019/12

no abstracts in English

Journal Articles

Density Functional Theory (DFT)-based bonding analysis correlates ligand field strength with $$^{99}$$Ru M$"o$ssbauer parameters of ruthenium-nitrosyl complexes

Kaneko, Masashi; Kato, Akane*; Nakashima, Satoru*; Kitatsuji, Yoshihiro

Inorganic Chemistry, 58(20), p.14024 - 14033, 2019/10

https://doi.org/10.1021/acs.inorgchem.9b02024
 Times Cited Count：10 Percentile：65.35(Chemistry, Inorganic & Nuclear)

We applied density functional theory calculations to ruthenium-nitrosyl complexes, which are known to exist in high-level radioactive waste, to give a theoretical correlation between $$^{99}$$Ru M$"o$ssbauer spectroscopic parameters ($$delta$$ and $$Delta$$$$E_{rm Q}$$) and ligand field strength ($$Delta$$$$_{rm o}$$) for the first time. The structures of the series of complexes, [Ru(NO)L$$_{5}$$] (L = Br$$^{-}$$, Cl$$^{-}$$, NH$$_{3}$$, CN$$^{-}$$), were modeled based on the corresponding single-crystal X-ray coordinates. The comparisons of the geometries and total energies between the different spin states suggested that the singlet spin state of [Ru(II)(NO$$^{+}$$)L$$_{5}$$] complexes were the most stable. The calculated results of both the $$delta$$ and $$Delta$$$$E_{rm Q}$$ values reproduced the experimental results by reported previously and increased in the order of L = Br$$^{-}$$, Cl$$^{-}$$, NH$$_{3}$$, CN$$^{-}$$. Finally, we estimated the ligand field strength ($$Delta$$$$_{rm o}$$) based on molecular orbitals, assuming C$$_{rm 4v}$$ symmetry and showed the increase of $$Delta$$$$_{rm o}$$ values in that order, being consistent with well-known spectrochemical series of ligands. The increase attributes to the strengthening of the abilities of $$sigma$$-donor and $$pi$$-acceptor of the L-ligands to the Ru atom, resulting in the increase of the $$delta$$ values.

Journal Articles

Magnetic field induced triple-$$q$$ magnetic order in trillium lattice antiferromagnet EuPtSi studied by resonant X-ray scattering

Tabata, Chihiro*; Matsumura, Takeshi*; Nakao, Hironori*; Michimura, Shinji*; Kakihana, Masashi*; Inami, Toshiya*; Kaneko, Koji; Hedo, Masato*; Nakama, Takao*; Onuki, Yoshichika*

Journal of the Physical Society of Japan, 88(9), p.093704_1 - 093704_5, 2019/09

https://doi.org/10.7566/JPSJ.88.093704
 Times Cited Count：29 Percentile：89.11(Physics, Multidisciplinary)

Journal Articles

Unique helical magnetic order and field-induced phase in trillium lattice antiferromagnet EuPtSi

Kaneko, Koji; Frontzek, M. D.*; Matsuda, Masaaki*; Nakao, Akiko*; Munakata, Koji*; Ohara, Takashi; Kakihana, Masashi*; Haga, Yoshinori; Hedo, Masato*; Nakama, Takao*; et al.

Journal of the Physical Society of Japan, 88, p.013702_1 - 013702_5, 2019/01

https://doi.org/10.7566/JPSJ.88.013702
 Times Cited Count：50 Percentile：95.2(Physics, Multidisciplinary)

Journal Articles

Benchmark study of DFT with Eu and Np M$"o$ssbauer isomer shifts using second-order Douglas-Kroll-Hess Hamiltonian

Kaneko, Masashi; Watanabe, Masayuki; Miyashita, Sunao*; Nakashima, Satoru*

Hyperfine Interactions, 239(1), p.20_1 - 20_10, 2018/12

BB2017-0056.pdf:0.5MB

https://doi.org/10.1007/s10751-018-1495-1
 Times Cited Count：4 Percentile：88.29

We optimized a mixing ratio of exchange energy between pure DFT and exact Hartree-Fock using TPSS exchange-correlation functional to estimate the accurate coordination bonds in f-block complexes by numerically benchmarking with the experimental data of M$"o$ssbauer isomer shifts for $$^{151}$$Eu and $$^{237}$$Np nuclides. Second-order Douglas-Kroll-Hess Hamiltonian with segmented all-electron relativistically contracted basis set was employed to calculate the electron densities at Eu and Np nuclei, i.e. contact densities, for each five complexes for Eu(III) and Np(IV) systems. We compared the root mean square deviation values of their isomer shifts between experiment and calculation by changing the mixing ratio of Hartree-Fock exchange parameter from 0 to 100 % at intervals of 10 %. As the result, it was indicated that the mixing ratio of 30 and 60 % for Eu and Np benchmark systems, respectively, gives the smallest deviation values. Mulliken's spin population analysis indicated that the covalency in the metal-ligand bonds for both Eu and Np complexes decreases with increasing the Hartree-Fock exchange admixture.

Journal Articles

On/off spin-crossover phenomenon and control of the transition temperature in assembled Iron(II) complexes

Nakashima, Satoru*; Kaneko, Masashi; Yoshinami, Keisuke*; Iwai, Saki*; Dote, Haruka*

Hyperfine Interactions, 239(1), p.39_1 - 39_15, 2018/12

https://doi.org/10.1007/s10751-018-1512-4
 Times Cited Count：2 Percentile：70.63

The present study reveals the on/off of spin-crossover (SCO) phenomenon in assembled Fe(II) complexes bridged by bis(pyridyl) type ligand. Whether SCO phenomenon occurs or not in assembled Fe(II) complexes bridged by bis(pyridyl) type ligand is determined by local structure around iron atom. SCO phenomenon occurs when the coordinating pyridines facing to each other across the iron atom are propeller type, while the phenomenon does not occur when they are parallel type or distorted propeller type. DFT calculation explained that, in the shortening of Fe-pyridine bonds when changing from high-spin state to low-spin state, the pyridines of propeller type can approach the iron atom with smaller steric hindrance than those of parallel and distorted propeller type complexes. The local structure is controlled by introducing methyl substituent and introducing $$pi$$-system, changing SCO phenomenon. And the transition temperature of SCO is also controlled in assembled complexes bridged by 1,2-bis(4-pyridyl)ethane by mixing anionic ligand.

98 (Records 1-20 displayed on this page)