Dimensional Control in Polyoxometalate Crystals Hybridized with Amphiphilic Polymerizable Ionic Liquids.

Toshiyuki Misawa,Shinichi Koguchi,Masashi Higuchi,Seiji Ono,Jun Kobayashi,Takeru Ito,Yosuke Okamura,Yoshiki Kiyota,Masayuki Watanabe,Yu Nagase

doi:10.3390/ma12142283

Abstract

Ionic liquids are an important component for constructing functional materials, and polyxometalate cluster anion is a promising partner for building inorganic–organic hybrid materials comprising ionic liquids. In such hybrid materials, the precise control of the molecular arrangement in the bulk structures is crucial for the emergence of characteristic functions, which can be realized by introducing an amphiphilic moiety into the ionic liquids. Here, an amphiphilic polymerizable imidazolium ionic liquid with a methacryloyl group was firstly hybridized with polyoxometalate anions of octamolybdate ([Mo8O26]4−, Mo8) and silicotungstate ([SiW12O40]4−, SiW12) to obtain inorganic–organic hybrid crystals. The polymerizable ionic liquid with a octyl chain (denoted as MAImC8) resulted in the formation of anisotropic molecular arrangements in the bulk crystal structure, which was compared with the hybrid crystals composed from the polymerizable ionic liquid without a long alkyl chain (denoted as MAIm). Rather densely packed isotropic molecular arrangements were observed in the hybrid crystals of MAIm–Mo8 and MAIm–SiW12 due to the lack of the amphiphilic moiety. On the other hand, using the amphiphilic MAImC8 cation gave rise to a honeycomb-like structure with the Mo8 anion and a layered structure with the SiW12 anion, respectively.

Highlights

Ionic liquid molecules attract extensive attention from researchers owing to their characteristic properties such as conductivity, catalysis, and separation abilities [1,2,3,4,5,6,7,8,9,10,11]
In the range of 400–1000 cm−1 together with the peaks derived from MAIm or MAImC8, indicating the successful hybridization of Mo8 with the polymerizable ionic liquids
Powder X-ray diffraction (XRD) patterns of as-prepared 4 (Figure 7c) were essentially similar to the patterns calculated from the single crystal structure of 4 (Figure 7d), indicating that the crystal structures of 4 were retained before and after the recrystallization. These results suggest that the amphiphilic moiety of the polymerizable ionic liquid enabled formation of the stable crystal structures of 4 owing to the van der Waals interactions between the octyl chains

Summary

Introduction

Ionic liquid molecules attract extensive attention from researchers owing to their characteristic properties such as conductivity, catalysis, and separation abilities [1,2,3,4,5,6,7,8,9,10,11]. These properties are quite attractive for the construction of functional materials. Introducing amphiphilic moieties, such as a long alkyl chain [30,31,32,33,34,35,36] in ionic liquids

Methods

Results

Conclusion