Manufacturing technologies
Magnetic cooling materials, Pesticides detoxification

図２．合成された希土類水酸化物クラスターの構造
Figure 2. Structures of a series of lanthanide hydroxide clusters.

Formation of lanthanide clusters in crystal lattice using ioniccrystals
今野巧

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Department of Chemistry, Graduate School of Science
Associate Professor Nobuto Yoshinari

Researchmap https://researchmap.jp/read0151149?lang=en

Professor Takumi Konno

Researchmap https://researchmap.jp/takumikonno?lang=en

Professor Yasuhiro Nakazawa

Researchmap https://researchmap.jp/thermo102?lang=en
吉成信人Abstract
It is well known that lanthanide hydroxide clusters show intriguing photophysical, magnetic, and catalytic properties. However,the controlled synthesis of this class of clusters is still challenging
due to the high pH responsibility and the geometrical flexibility oflanthanide ions. In this study, we developed a simple synthetic
method to obtain lanthanide hydroxide clusters using the post-synthetic installation of lanthanide ions inside ionic crystals. Soaking
ionic crystals of K6[Rh4Zn4O(L-cysteinate)6] in a solution of late lanthanide acetate led to the exchange of potassium ions by lanthanide ions to form lanthanide hydroxide clusters in the crystal lattice.
In addition, the crystals installed by lanthanide clusters showed
potential applications for magnetic cooling and catalytic hydrolysisof phosphate esters.

今野巧

中澤康浩

MOF-type framework that is insoluble in solution. The crystals containing lanthanide clusters showed an excellent magnetic coolingand an effective catalytic ability for esters hydrolysis, contributing
to the development of magnetic cooling devices and detoxification
agents of pesticides.

中澤康浩

Manufacturing technologies▍ Background & Results
The post-synthetic modification (PSM) of crystalline materials is
one of the methods to synthesize new compounds that are difficult
to synthesize by conventional processes. In this study, we found
the formation of lanthanide cubane clusters inside ionic crystals ofcoordination compounds through the PSM process.
We used ionic crystals of K6[Rh4Zn4O(L-cysteinate)6] that have recently been synthesized by us as the host crystals, which showedsuperionic conduction due to potassium ions. Immersing the hostcrystals in an EtOH/H2O solution containing excess Ln(OAc)3 (Ln =GdIII, TbIII, DyIII, ErIII, HoIII, TmIII, YbIII, LuIII) at room temperature gave
new crystals containing cubane-type lanthanide hydroxide clusters
Ln4(OH)4 via single-crystal-to-single-crystal transformation. In thecrystal, each lanthanide cubane cluster is bound by free carboxylate groups of the [Rh4Zn4O(L-cysteinate)6]6- anions to construct an
infinitely connected MOF structure. A preliminary magnetic coolingexperiment indicated that crystals containing Gd3+ cubane clusters
were cooled down from 2.6 K to 1.8 K by reducing the magneticfield from 5T to 2T. The magnetic cooling below 2 K is very remarkable because the cooling below 2 K is achieved only by theuse of 3He that is a rare and expensive resource. Moreover, all thecrystals containing Ln3+ cubane clusters showed good heterogeneous catalytic activities for the hydrolysis of phosphate esters in anaqueous media. Since phosphate esters are used as a pesticide inagriculture, which is a cause of water pollution in many countries,
the crystals synthesized in this study are applicable for the detoxification of agricultural wastewaters and products.

Figure 1．Schematic illustration of the synthesis of lanthanide hydroxide clusters incrystal▍ Significance of the research and Future perspective
The present study revealed that the lanthanide hydroxide clusters are easily synthesized inside the pore of ionic crystals of thecoordination compound via soaking crystals in a solution containing lanthanide acetate at room temperature. The resulting lanthanide clusters are tightly fixed in the crystal lattice to construct aFigure 2. Structures of a series of lanthanide hydroxide clusters.

P a t e n t Japanese Patent Application No. 2020-122934, PCT/JP/2021/02679
Yoshinari, Nobuto; Konno, Takumi et al. Single-Crystal-to-Single-Crystal Installation of Ln4(OH)4 Cubanes in an Anionic Metallosupramolecular Framework.
Tr e a t i s eAngew. Chem. Int. Ed Engl. 2020; 59(41): 18048-18053. doi; 10.1002/anie.202008296
UR
L http://www.chem.sci.osaka-u.ac.jp/lab/konno/index_e.html
K e y w o r d rare-earth elements, metal clusters, magnetic cooling, heterogeneous catalysis