A Bowl-Type Dodecavanadate as a Halide Receptor

Sho Kuwajima; Yuka Ikinobu; Daiki Watanabe; Yuji Kikukawa; Yoshihito Hayashi; Atsushi Yagasaki

doi:10.1021/acsomega.6b00408

A Bowl-Type Dodecavanadate as a Halide Receptor

ACS Omega. 2017 Jan 26;2(1):268-275. doi: 10.1021/acsomega.6b00408. eCollection 2017 Jan 31.

Authors

Sho Kuwajima¹, Yuka Ikinobu¹, Daiki Watanabe¹, Yuji Kikukawa^{1

2}, Yoshihito Hayashi¹, Atsushi Yagasaki³

Affiliations

¹ Department of Chemistry, Graduate School of Natural Science and Technology, Kanazawa University, Kakuma, Kanazawa 920-1192, Ishikawa, Japan.
² JST, PRESTO, 4-1-8 Honcho, Kawaguchi 332-0012, Saitama, Japan.
³ Department of Chemistry, Kwansei Gakuin University, Sanda 669-1337, Hyogo, Japan.

Abstract

The dodecavanadate framework, [V₁₂O₃₂]^4-, exhibits a unique bowl-type structure with an open molecular oxide cage having a cavity diameter of 4.4 Å, and different synthetic paths were required to construct the bowl-type structure with a different guest. A new dodecavanadate, {(n-C₄H₉)₄N}₄[V₁₂O₃₂(CH₃NO₂)] (1), is synthesized with a nitromethane guest, which is stacked above the entrance of the hemisphere rather than fully occupying the cavity, and it enables a guest-capturing reaction, while retaining the anionic cage structure. Compound 1 is a good precursor for halide-centered dodecavanadates, {(C₂H₅)₄N}₅[V₁₂O₃₂(X)] (X = Cl^- (2), Br^- (3), and I^- (4)). The position of the halide inside the cavity correlates with the ionic radius of the guest; the small chloride ion sat at the far bottom, and the large iodide floated at the entrance. The inclusion reaction rates were estimated through ⁵¹V NMR time-course measurements in nitromethane. The reaction rates increase in the order I^- < Br^- < Cl^-.