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complexes of mixed N,O-donor ligands demonstrated on a 10-fold [Eu(TPAMEN)] chelate complexSchnaars, K.; Kaneko, Masashi; Fujisawa, Kiyoshi*
Inorganic Chemistry, 60(4), p.2477 - 2491, 2021/02
Times Cited Count：6 Percentile：57.56(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 
-tetrakis[(6-carboxypyridin-2-yl)methyl]ethylenediamine (H
TPAEN) has shown good performance as a masking agent in Am/Eu separation studies. In this work, we examine whether a decrease in O-donor basicity can promote the M-N
interactions. Therefore, we replace the deprotonated "charged" carboxylic acid groups of TPAEN
by neutral amide groups and introduce -tetrakis[(6-
-diethylcarbamoylpyridin-2-yl)methyl]ethylenediamine (TPAMEN) as a new ligand. TPAMEN was crystallized with Eu(OTf)
and Eu(NO) 6H
O to form positively charged 1:1 [Eu(TPAMEN)] 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 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)] (M = Eu, Am) complexes provide an outlook on the potential performance of TPAMEN in Am/Eu separation.
Kakurai, Kazuhisa; Osakabe, Toyotaka; Goto, Kenji*; Osawa, Akira*; Fujisawa, Masashi*; Tanaka, Hidekazu*
Physica B; Condensed Matter, 385-386(Part 1), p.450 - 452, 2006/11
Times Cited Count：1 Percentile：6.63(Physics, Condensed Matter)KCuCl and TlCuCl are singlet ground state systems with excitation gap of 31K and 7.7K, respectively. The origin of the spin gap is the strong antiferromagnetic spin dimer of the chemical CuCl
unit. These spin dimers are weakly coupled three dimensionally via non-frustrating inter dimer exchanges. The magnetization measurements under applied hydrostatic pressure show the existence of the magnetic order above certain critical pressure Pc=8.8 kbar and 0.42 kbar, respectively. We report on the elastic neutron scattering results of the pressure induced magnetic ordering in these quantum systems. The observed magnetic structures and the possible role of the spin-lattice coupling in the spin reorientation in TlCuCl3 under pressure will be discussed.
Goto, Kenji; Fujisawa, Masashi*; Tanaka, Hidekazu*; Uwatoko, Yoshiya*; Osawa, Akira*; Osakabe, Toyotaka; Kakurai, Kazuhisa
Journal of the Physical Society of Japan, 75(6), p.064703_1 - 064703_7, 2006/06
Times Cited Count：30 Percentile：76.29(Physics, Multidisciplinary)Magnetization and neutron elastic scattering experiments under hydrostatic pressure were performed on KCuCl, which is a three-dimensionally coupled spin dimer system with a gapped ground state. It was found that the intradimer interaction decreases with increasing hydrostatic pressure, while the sum of the interdimer interactions increases. This leads to the shrinkage of the spin gap. A quantum phase transition from a gapped state to an antiferromagnetic state occurs at Pc
8.2 kbar. For P
Pc, magnetic reflections were observed at reciprocal lattice points equivalent to those for the lowest magnetic excitation at zero temperature. This confirms that the spin gap decreases and closes under applied pressure.
Osawa, Akira; Fujisawa, Masashi*; Osakabe, Toyotaka; Kakurai, Kazuhisa; Tanaka, Hidekazu*
Journal of the Physical Society of Japan, 72(5), p.1026 - 1029, 2003/05
Times Cited Count：60 Percentile：87.54(Physics, Multidisciplinary)no abstracts in English
Mg
)ClOsawa, Akira; Fujisawa, Masashi*; Kakurai, Kazuhisa; Tanaka, Hidekazu*
Physical Review B, 67(18), p.184424_1 - 184424_8, 2003/05
Times Cited Count：31 Percentile：77.47(Materials Science, Multidisciplinary)no abstracts in English
and KCuCl under applied pressureGoto, Kenji*; Fujisawa, Masashi*; Osawa, Akira*; Kakurai, Kazuhisa; Osakabe, Toyotaka; Uwatoko, Yoshiya*; Tanaka, Hidekazu*
no journal, ,
no abstracts in English
Cl
H
CSOFujisawa, Masashi*; Shiraki, Kosuke*; Okubo, Susumu*; Ota, Hitoshi*; Yoshida, Makoto*; Tanaka, Hidekazu*; Sakai, Toru
no journal, ,
The spin dynamics of the quasi-one-dimensional antiferromagnet CuClHCSO was investigated by the electron spin resonance (ESR). The system has a spin gap, but the direct ESR transition of the spin gap is forbidden due to the spin conservation law, because the spin gap is an energy gap between the singlet and triplet states. However, the direct ESR transition of the spin gap was observed for this material. The present study revealed that the origin of the direct ESR transition is the Dzyaloshinsky-Moriya interaction, and applying the selection rule of the angle-dependent ESR intensity, we successfully specified the direction of the interaction vector.
