A redox-active inorganic crown ether based on a polyoxometalate capsule

Nanako Tamai; Naoki Ogiwara; Eri Hayashi; Keigo Kamata; Toshiyuki Misawa; Takeru Ito; Tatsuhiro Kojima; Mireia Segado; Enric Petrus; Carles Bo; Sayaka Uchida

doi:10.1039/d3sc01077e

A redox-active inorganic crown ether based on a polyoxometalate capsule

Chem Sci. 2023 Apr 26;14(20):5453-5459. doi: 10.1039/d3sc01077e. eCollection 2023 May 24.

Authors

Nanako Tamai¹, Naoki Ogiwara¹, Eri Hayashi², Keigo Kamata², Toshiyuki Misawa³, Takeru Ito³, Tatsuhiro Kojima⁴, Mireia Segado⁵, Enric Petrus⁵, Carles Bo^{5

6}, Sayaka Uchida¹

Affiliations

¹ Department of Basic Science, School of Arts and Sciences, The University of Tokyo 3-8-1 Komaba, Meguro-ku Tokyo 153-8902 Japan csayaka@g.ecc.u-tokyo.ac.jp.
² Laboratory for Materials and Structures, Institute of Innovative Research, Tokyo Institute of Technology Nagatsuta-cho 4259, Midori-ku Yokohama 226-8503 Japan.
³ Department of Chemistry, School of Science, Tokai University 4-1-1 Kitakaname Hiratsuka 259-1292 Japan.
⁴ Department of Chemistry, Graduate School of Science, Osaka Univerisity 1-1 Machikaneyamacho Toyonaka Osaka 560-0043 Japan.
⁵ Institute of Chemical Research of Catalonia (ICIQ), The Barcelona Institute of Science and Technology (BIST) Av. Països Catalans, 16 43007 Tarragona Spain.
⁶ Departament de Química Física i Inorgànica, Universitat Rovira i Virgili Marcel lí Domingo s/n 43007 Tarragona Spain.

Abstract

Cation-uptake has been long researched as an important topic in materials science. Herein we focus on a molecular crystal composed of a charge-neutral polyoxometalate (POM) capsule [Mo^VI₇₂Fe^III₃₀O₂₅₂(H₂O)₁₀₂(CH₃CO₂)₁₅]³⁺ encapsulating a Keggin-type phosphododecamolybdate anion [α-PMo^VI₁₂O₄₀]^3-. Cation-coupled electron-transfer reaction occurs by treating the molecular crystal in an aqueous solution containing CsCl and ascorbic acid as a reducing reagent. Specifically, multiple Cs⁺ ions and electrons are captured in crown-ether-like pores {Mo^VI₃Fe^III₃O₆}, which exist on the surface of the POM capsule, and Mo atoms, respectively. The locations of Cs⁺ ions and electrons are revealed by single-crystal X-ray diffraction and density functional theory studies. Highly selective Cs⁺ ion uptake is observed from an aqueous solution containing various alkali metal ions. Cs⁺ ions can be released from the crown-ether-like pores by the addition of aqueous chlorine as an oxidizing reagent. These results show that the POM capsule functions as an unprecedented "redox-active inorganic crown ether", clearly distinguished from the non-redox-active organic counterpart.