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Article

Dimensional Control in Polyoxometalate Crystals Hybridized with Amphiphilic Polymerizable Ionic Liquids

by
Toshiyuki Misawa
1,
Jun Kobayashi
1,
Yoshiki Kiyota
1,
Masayuki Watanabe
2,
Seiji Ono
2,
Yosuke Okamura
2,
Shinichi Koguchi
1,
Masashi Higuchi
2,
Yu Nagase
2 and
Takeru Ito
1,*
1
Department of Chemistry, School of Science, Tokai University, 4-1-1 Kitakaname, Hiratsuka 259-1292, Japan
2
Department of Applied Chemistry, School of Engineering, Tokai University, 4-1-1 Kitakaname, Hiratsuka 259-1292, Japan
*
Author to whom correspondence should be addressed.
Materials 2019, 12(14), 2283; https://doi.org/10.3390/ma12142283
Submission received: 19 June 2019 / Revised: 12 July 2019 / Accepted: 15 July 2019 / Published: 16 July 2019
(This article belongs to the Special Issue Growth and Design of Inorganic Crystal)
Browse Figures
Versions Notes

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.

1. 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. The hybridization of ionic liquids as organic components with other inorganic counter parts is effective for building up functional inorganic–organic hybrid materials. To select inorganic counter parts for the hybridization is crucial for improving the thermal stability and other properties.
Polyoxometalate (POM) cluster anions are effective inorganic components for constructing inorganic–organic hybrid materials due to their characteristic physicochemical properties [12,13,14,15,16,17,18,19,20]. Hybridization of ionic liquids with POMs has been investigated, and several functional hybrids have been successfully realized such as solid electrolytes or catalysts [21,22,23,24,25,26,27,28]. These ionic liquid–POM hybrids sometimes have POM arrangements in a disordered manner, which may be a drawback for exploiting their characteristics in solid-state hybrid materials. The dimensional control of the components in the solid state is quite significant for the emergence and control of characteristic properties [29]. Introducing amphiphilic moieties, such as a long alkyl chain [30,31,32,33,34,35,36] in ionic liquids is an effective way of constructing single-crystalline ordered structures in the ionic liquid–POM hybrids [37,38,39,40,41].
Recently, we designed a polymerizable ionic liquid cation with an imidazolium moiety with a methacryloyl group ([{CH2=C(CH3)COO(CH2)2}C3H3N2(CH3)]+, denoted as MAImC1, Figure 1a), and successfully synthesized inorganic–organic hybrid monomers and polymers with several POM anions [42,43,44]. These MAImC1–POM hybrids were isolated as single crystals with clarified structures, and behaved as monomers of hybrid polymers exhibiting high conductivity as solid electrolytes [44]. In the MAImC1–POM hybrid monomers, the POM arrangements in the bulk crystal structures were isotropic due to the small molecular size of the MAImC1 cation. Introducing an amphiphilic moiety into MAImC1 will give rise to a more anisotropic molecular arrangement of POM anions derived from the structure-directing ability of the amphiphilic moiety [30,31,32].
Here we report the first syntheses of POM hybrid crystals with amphiphilic polymerizable ionic liquids. The amphiphilic polymerizable ionic liquid is a MAImC1 derivative with a long octyl chain instead of a methyl group ([{CH2=C(CH3)COO(CH2)2}C3H3N2(C8H17)]+, denoted as MAImC8, Figure 1a). Another MAImC1 derivative without a methyl group ([{CH2=C(CH3)COO(CH2)2}C3H4N2]+, denoted as MAIm, Figure 1a) was also utilized to hybridize with POM anions for comparison. The POM anions hybridized were β-type octamolybdate ([Mo8O26]4– (Mo8), Figure 1b) and dodecatungstosilicate ([SiW12O40]4– (SiW12), Figure 1b), both of which are anions with a 4− charge. Hybrid crystals with Mo8 and SiW12 have been reported previously [42,44]. The hybrid crystals with MAImC8 contained anisotropic arrangements of POM anions in their bulk crystal structures due to the presence of an amphiphilic moiety, while hybrid crystals with MAIm exhibited isotropic POM arrangements.

2. Materials and Methods

2.1. Materials and General Methods

All chemical reagents were purchased from FUJIFILM Wako Pure Chemical Corporation (Osaka, Japan) and Tokyo Chemical Industry Co., Ltd. (TCI, Tokyo, Japan). The starting polymerizable ionic liquid of [{CH2=C(CH3)COO(CH2)2}C3H3N2] (denoted as MAIm–N) was synthesized as a neutral compound, and [{CH2=C(CH3)COO(CH2)2}C3H3N2(C8H17)]Br (MAImC8·Br) were synthesized as bromide salts according to previous studies (Figure S1) [42,43,44].
Infrared (IR) spectra were recorded on a Jasco FT/IR-4200ST spectrometer (JASCO Corporation, Tokyo, Japan) by the KBr pellet method. Powder X-ray diffraction (XRD) patterns were measured with a Rigaku MiniFlex300 diffractometer (Rigaku Corporation, Tokyo, Japan) by using Cu Kα radiation (λ = 1.54056 Å) at ambient temperature. CHN (carbon, hydrogen, and nitrogen) elemental analyses were performed with a PerkinElmer 2400II elemental analyzer (PerkinElmer, Waltham, MA, USA).

2.2. Syntheses of Polyoxometalate Hybrids with Polymerizable Ionic Liquids

2.2.1. Synthesis of MAIm–Mo8

As-prepared MAIm–Mo8 (denoted as 1) was initially precipitated by a cation exchange reaction. Na2MoO4·2H2O (1.0 g, 4.1 mmol) was dissolved in 10 mL of H2O, and then the pH was adjusted to 3.8 by 6 M HCl. To the obtained homogeneous solution was added an ethanol solution (10 mL) of MAIm–N (0.28 g, 1.6 mmol) neutralized by 1 M HCl (2.0 mL). The resulting suspension was filtered to obtain colorless precipitates, which was dried under ambient atmosphere to obtain colorless precipitates (0.73 g, yield: 48%). An acetonitrile/ethanol solution (20 mL, 1:1 (v/v)) of as-prepared 1 (0.03 g) was heated at ca. 343 K for 3 h, and then the supernatant was slowly evaporated at room temperature to obtain colorless plates of 1. CHN elemental analysis: Calcd for C30H45N6NaMo8O32: C: 18.53, H: 2.25, N: 4.80%. Found: C: 18.97, H: 2.30, N: 4.98%. IR (KBr disk): 3144 (w), 3109 (w), 3010 (w), 2979 (w), 2927 (w), 2883 (w), 1734 (m), 1718 (m), 1635 (m), 1577 (w), 1543 (w), 1456 (w), 1401 (w), 1362 (w), 1317 (w), 1301 (m), 1170 (m), 1086 (w), 1041 (w), 942 (s), 916 (s), 846 (m), 817 (w), 724 (s), 666 (m), 626 (w), 556 (w), 523 (w) cm−1.

2.2.2. Synthesis of MAImC8–Mo8

As-prepared MAImC8–Mo8 (denoted as 2) was synthesized and recrystallized by a similar procedure to 1. Na2MoO4·2H2O (0.51 g, 2.1 mmol) dissolved in 10 mL of H2O was adjusted to pH 3.8 by 6 M HCl, and then an ethanol solution (10 mL) of MAImC8·Br (0.30 g, 0.80 mmol) was added. The resulting suspension was filtered and dried to obtain colorless precipitates (0.38 g, yield: 47%). An acetonitrile/ethanol solution (20 mL, 1:1 (v/v)) of as-prepared 2 (0.03 g) was heated at ca. 343 K for 3 hours, and the supernatant was slowly evaporated at room temperature to obtain colorless plates of 2. CHN elemental analysis: Calcd for C51H87N6NaMo8O32: C: 29.10, H: 4.26, N: 3.99%. Found: C: 28.05, H: 4.14, N: 3.52%. IR (KBr disk): 3136 (w), 3105 (w), 2956 (m), 2925 (s), 2854 (m), 1719 (m), 1636 (w), 1560 (w), 1457 (w), 1404 (w), 1377 (w), 1362 (w), 1317 (w), 1296 (w), 1162 (m), 1039 (w), 943 (s), 913 (s), 844 (m), 714 (s), 666 (m), 555 (w), 525 (w), 473 (w), 453 (w), 442 (w), 416 (w) cm−1.

2.2.3. Synthesis of MAIm–SiW12

As-prepared MAIm–SiW12 (denoted as 3) was synthesized by adding a 10 mL ethanol solution containing MAIm–N (0.59 g, 3.3 mmol) to a 10 mL ethanol solution of dodecatungstosilicic acid 26 hydrate (H4[SiW12O40]·26H2O (H–SiW12), 2.0 g (0.60 mmol)). The obtained suspension was separated by decantation to obtain colorless precipitates, which were washed by water and dried under ambient atmosphere (1.3 g, yield: 51%). A 1,4-dioxane solution (20 mL) of as-prepared 3 (0.03 g) was heated at ca. 333 K for 3 h, and the supernatant was kept at 298 K to obtain colorless plates of 3. CHN elemental analysis: Calcd for C36H52N8SiW12O48: C: 12.01, H: 1.46, N: 3.11%. Found: C: 12.03, H: 1.47, N: 3.04%. IR (KBr disk): 3145 (w), 3072 (w), 2963 (w), 2927 (w), 1715 (m), 1634 (w), 1578 (w), 1547 (w), 1449 (w), 1404 (w), 1319 (w), 1297 (w), 1168 (m), 1085 (w), 1013 (w), 973 (s), 922 (s), 884 (w), 796 (s), 665 (w), 622 (w), 534 (w) cm−1.

2.2.4. Synthesis of MAImC8–SiW12

As-prepared MAImC8–SiW12 (denoted as 4) was synthesized and recrystallized by a similar procedure to 3. H–SiW12 (1.2 g, 0.36 mmol) was dissolved in 5 mL of ethanol, and then an ethanol solution (10 mL) of MAImC8·Br (0.50 g, 1.3 mmol) was added. The resulting suspension was filtered and dried under ambient atmosphere to obtain colorless precipitates (1.2 g, yield: 69%). An 1,4-dioxane/ethanol solution (20 mL, 1:1 (v/v)) of as-prepared 4 (0.03 g) was heated at ca. 333 K for 3 hours, and the supernatant was kept at 298 K to obtain colorless plates of 4. CHN elemental analysis: Calcd for C68H116N8SiW12O48: C: 19.50, H: 2.79, N: 2.74%. Found: C: 20.18, H: 2.89, N: 2.77%. IR (KBr disk): 3142 (w), 3109 (w), 2957 (w), 2925 (m), 2853 (m), 1719 (w), 1635 (w), 1561 (w), 1457 (w), 1401 (w), 1377 (w), 1359 (w), 1318 (w), 1295 (w), 1161 (w), 1107 (w), 1054 (w), 1013 (w), 973 (m), 920 (s), 884 (w), 795 (s), 653 (w), 530 (w), 487 (w), 423 (w) cm−1.

2.3. X-ray Crystallography

Single crystal X-ray diffraction measurements for 1–3 were performed with an ADSC Q210 CCD area detector by using synchrotron radiation (λ = 0.60000–0.80000 Å, Table 1) at 2D beamline in the Pohang Accelerator Laboratory (PAL, a synchrotron radiation facility in Pohang, Republic of Korea). The processing of both diffraction images and absorption correction were performed with HKL3000 [45]. The diffraction measurements for 4 were made on a Rigaku XtaLAB P200 diffractometer (Rigaku Corporation, Tokyo, Japan) using graphite monochromated Mo Kα radiation, and the data were collected and processed using CrysAlisPro [46]. The structures were solved by the dual-space algorithm using SHELXT Version 2014/5 [47] or SHELXS Version 2013/1 [48], and refined by the full-matrix least-squares method on F2 using SHELXL Version 2014/7 [48]. All calculations were performed using the CrystalStructure software package [49]. Most non-hydrogen atoms were refined anisotropically, and the hydrogen atoms of organic moieties were refined using the riding model. Further details of the crystal structure investigation may be obtained free of charge from the Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223 336 033; or E-Mail: [email protected] (CCDC 1934917–1934920).

3. Results

3.1. Mo8 hybrids with Polymerizable Ionic Liquids

Octamolybdate (Mo8) hybrids with the polymerizable ionic liquids of MAIm and MAImC8 were obtained as colorless precipitates in ca. 50% yield. IR spectra of both as-prepared MAIm–Mo8 (1, Figure 2a) and MAImC8–Mo8 (2, Figure 2c) exhibited characteristic peaks of the β-Mo8 anion [50,51,52] in the range of 400–1000 cm−1 together with the peaks derived from MAIm or MAImC8 (methylene groups in 2800–3000 cm−1 and methacryloyl group in 1200–1800 cm−1), indicating the successful hybridization of Mo8 with the polymerizable ionic liquids.
Both as-prepared precipitates of 1 and 2 were successfully recrystallized by using acetonitrile/ethanol solution to obtain single crystals. The IR spectra of recrystallized 1 (Figure 2b) were almost identical to that of the as-prepared 1 (Figure 2a), indicating that the molecular structures were retained before and after the recrystallization. The molecular structures of 2 were also the same before and after the recrystallization as observed in the IR spectra of hybrid crystal 2 (Figure 2c,d).
X-ray structure analyses together with CHN elemental analyses revealed that the Mo8 hybrid crystals were formulated to be [{CH2=C(CH3)COO(CH2)2}C3H4N2]3Na[Mo8O26] for 1 and [{CH2=C(CH3)COO(CH2)2}C3H3N2(C8H17)]3Na[Mo8O26] for 2, respectively (Table 1, Figure 3). Both hybrid crystals contained three MAIm (1+ charge) or MAImC8 (1+ charge) and one Na+ associated with one β-type Mo8 anion (4− charge), being similar to other hybrid crystals consisting of β-type Mo8 anions [42,53,54]. Both crystal structures contained a one-dimensional (1D) infinite chain composed of the Na+ cation and Mo8 anion (Mo8–Na+ 1D chain) as shown in Figure 3a,b, while the coordination environments of Na+ were different. The Na+ cation in 1 was surrounded by O atoms of two Mo8 anions and two MAIm cations, and located in a six-fold coordination environment (Na–O distance: 2.28–2.43 Å, mean value: 2.36 Å) to form a zig-zag chain structure (Figure 3a, right). On the other hand, the Na+ cation in 2 was sandwiched by only two β-Mo8 anions to possess an eight-fold coordination environment (Na–O distance: 2.40−2.90 Å, mean value: 2.60 Å), resulting in a more straight chain structure (Figure 3b, right).
In addition, the packing manners of the Mo8–Na+ 1D chains in the crystal structures of 1 and 2 were different. The Mo8–Na+ 1D chains in 1 were rather densely packed in the crystal structure (Figure 3a, left), while the Mo8–Na+ 1D chains in 2 were located more separately, to exhibit a honeycomb-like structure along the a-axis direction (Figure 3b, left). Namely, 1 had a rather isotropic arrangement of the Mo8–Na+ 1D chains, while 2 possessed a more anisotropic arrangement of the Mo8–Na+ 1D chains in the bulk crystal structure. This difference in the arrangements of the Mo8–Na+ 1D chains between 1 and 2 will be due to the presence of the amphiphilic moiety in the polymerizable ionic liquid cations. The MAImC8 had a long alkyl chain, which interacted with itself to control the arrangement of the Mo8–Na+ 1D chain in the crystal structures of 2 [30,31,32]. As shown in Figure 3c, several C–C bonds in the methylene groups of MAImC8 had a gauche conformation, which forced both octyl and methacryloyl groups to locate to the same side against the charged and hydrophilic imidazolium ring. These molecular conformations of MAImC8 caused the segregation of hydrophilic and hydrophobic parts in the crystal structure of 2, resulting in the anisotropic honeycomb-like arrangement of the Mo8–Na+ 1D chains (Figure 3b, left). The octyl chains were not interdigitated in a straight manner.
Powder XRD patterns of as-prepared 1 and 2 (Figure 4a,c) were quite similar in the peak positions to the patterns calculated from the single crystal structure of 1 and 2 (Figure 4b,d), indicating that the crystal structures of 1 and 2 were retained before and after the recrystallization. Slight differences in the peak intensity and position of the patterns may be derived from the difference in the measurement temperature (powder: ambient temperature, single crystal: 100 K). This suggests that the Mo8–Na+ 1D chains were already formed in the as-prepared precipitates due to their stable and rigid structures. The amphiphilic moiety of MAImC8 in 2 also contributed to the formation of a stable and rigid crystal structure derived from the van der Waals interactions between the octyl chains.

3.2. SiW12 Hybrids with Polymerizable Ionic Liquids

Dodecatungstosilicate (SiW12) hybrids with the polymerizable ionic liquids were obtained as colorless precipitates in ca. 50% yield for MAIm–SiW12 (3) and ca. 70% yield for MAImC8–SiW12 (4), respectively. The characteristic peaks of SiW12 [17,44,55] were observed for as-prepared 3 (Figure 5a) and 4 (Figure 5c) in the range of 400–1100 cm−1 of IR spectra. The presence of the polymerizable ionic liquids were confirmed by the IR spectra (in the range of 2800–3000 cm−1 for methylene groups and 1200–1800 cm−1 for methacryloyl group), which showed successful formation of the hybrid crystals comprising SiW12 and the polymerizable ionic liquids.
Single crystals of 3 were obtained from 1,4-dioxane (C4H4O2) solution, while single crystals of 4 were grown from 1,4-dioxane/ethanol solution. As-prepared 3 (Figure 5a) and recrystallized 3 (Figure 5b) were almost the same in the IR spectra, indicating the retention of the molecular structures before and after the recrystallization. A slight difference in the peaks in the range of 1500–1700 cm−1 may be derived from the difference in the crystal structures of as-prepared 3 and recrystallized 3 (see below). The retention of the molecular structures of 4 was also verified by the IR spectra measured before and after the recrystallization (Figure 5c,d).
Chemical formulae were revealed to be [{CH2=C(CH3)COO(CH2)2}C3H4N2]4[SiW12O40]·C4H4O2 for 3 and [{CH2=C(CH3)COO(CH2)2}C3H3N2(C8H17)]4[SiW12O40]·C4H4O2·H2O for 4, respectively (Table 1). These hybrid crystals contained four polymerizable ionic liquid cations (1+ charge) associated with one SiW12 anion (4− charge). All of the protons of the starting H–SiW12 were replaced by ion-exchange reactions without remaining counter cations after the hybridization [44,56,57,58], which was different from the cases of Mo8 hybrid crystals of 1 and 2. Both recrystallized SiW12 hybrid crystals of 3 and 4 contained the solvents of crystallization (1,4-dioxane utilized in the recrystallization process for 3; 1,4-dioxane and water for 4), which also contrasts with the Mo8 hybrid crystals of 1 and 2. Figure 6 depicts crystal structures of 3 (Figure 6a) and 4 (Figure 6b). In both crystals, each SiW12 anion was isolated by the imidazolium moieties of the polymerizable ionic liquids (Figure 6a, right for 3; Figure 6b, right for 4).
The molecular arrangements of the SiW12 anions in the bulk crystal structures of 3 and 4 were quite different. The SiW12 anions are arranged rather densely and isotropically in 3 (Figure 6a, left). On the contrary, the SiW12 anions in 4 formed the inorganic monolayers sandwiched by the MAImC8 organic layers with an interlayer distance of 20.2 Å (Figure 6b, left), and exhibited much more anisotropic structure than 3. Such anisotropic molecular arrangement will be induced by the amphiphilic moiety of the MAImC8 cations. The MAImC8 in 4 had similar conformations to those observed in 2 (Figure 3c). The octyl chains in 4 were not interdigitated in a straight manner as in the crystals of 2.
The powder XRD pattern of as-prepared 3 (Figure 7a) was different from that calculated from the single crystal structure of 3 (Figure 7b). This demonstrates that the crystal structures of 3 changed after the recrystallization, probably because of desolvation of solvent molecules of the crystals under the ambient atmosphere. On the other hand, powder 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.

4. Discussion

As observed in the crystal structures of 2 and 4, introducing the amphiphilic moiety into the polymerizable ionic liquid enabled the construction of the anisotropic molecular arrangements of POM inorganic clusters in the bulk crystal structures. The amphiphilic MAImC8 cation behaved as a structure-directing reagent, like typical surfactants [30,31,32], owing to the van der Waals interactions between the octyl chains of MAImC8. The presence of a long alkyl chain in the polymerized ionic liquids induced the segregation of hydrophilic parts (charged POM and imidazolium ring) and a hydrophobic moiety (alkyl chain and methacryloyl group), which led to the formation of the anisotropic POM arrangements in the crystal structures of 2 and 4. Introducing the amphiphilic moiety into the polymerizable ionic liquid also realized stable crystal structures. The crystal structures of 2 and 4 were retained before and after the recrystallization process, although the crystal structures of the hybrid crystal of 3 without the amphiphilic moiety changed in their crystal structures through the recrystallizations procedures.
The β-type Mo8 anion tends to coordinate metal cations to form a 1D chain or two-dimensional (2D) layered structures [42,54]. The smaller metal cations such as Na+ or Ag+ preferred the 1D chain structure, while the larger cations such as K+ or Cs+ gave rise to a 2D layered structure. In the case of 1 and 2, the Na+ cation of the starting material (Na2MoO4·2H2O) remained to form the Mo8–Na+ 1D chain structures in the crystal structures. Furthermore, 1 and 2 kept their molecular and crystal structures before and after the recrystallization (Figure 2 and Figure 4), suggesting the retention of the Mo8–Na+ 1D chain structures. These stable Mo8–Na+ 1D chain structures could be beneficial to the Na+-conducting materials. On the other hand, the typical Keggin-type SiW12 anion exhibits Td symmetry, which is higher than the C2h symmetry of the β-Mo8 anion (Figure 1b) [59,60]. The more spherical SiW12 anion tends to be surrounded by the heterocyclic moiety of the polymerizable ionic liquid or surfactant [44,56], resulting in the isolated arrangement of SiW12 without the coordination by metal cations.
As described here, introducing the amphiphilic moiety into the polymerizable ionic liquid is an effective way to control the POM arrangements in the hybrid single crystals. Such controlled arrangement of POM anions will have beneficial emergent functions such as conductive properties [12,13,29]. In principle, these POM hybrid crystals of 1–4 behave as inorganic–organic hybrid monomers to construct hybrid polymers [20,42,43,44], which could pave the way to another category of conductive materials. The polymerization of these hybrids and investigation of conductivities are in progress.

5. Patents

A Japanese patent (JP 2018012758 A) resulted from the work reported in this manuscript (T.I., Y.N., S.K., M.H., Y.O.).

Supplementary Materials

The following are available online at https://www.mdpi.com/1996-1944/12/14/2283/s1, synthetic procedures of polymerizable ionic liquids, Figure S1: Synthetic route of MAIm, cif files of 1–4.

Author Contributions

Conceptualization, T.I. and Y.N.; methodology, T.I., Y.N., S.K., M.H., Y.O.; formal analysis, T.M., M.W., S.O., T.I.; investigation, T.M., J.K., Y.K., M.W., S.O.; resources, S.K.; writing—original draft preparation, T.I.; visualization, T.M., T.I.; funding acquisition, T.I.

Funding

This research was funded in part by JSPS KAKENHI (grant No. JP26410245), Research and Study Project of Tokai University Educational System General Research Organization (grant No. PJ2014-02), and JSPS Core-to-Core Program. The APC was funded by Iketani Science and Technology Foundation (grant No. 0311048-A).

Acknowledgments

X-ray diffraction measurements with synchrotron radiation were performed at the Pohang Accelerator Laboratory (Beamline 2D), a synchrotron radiation facility in Pohang, Republic of Korea, supported by Pohang University of Science and Technology (POSTECH).

Conflicts of Interest

The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.

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Materials 12 02283 g001 550
Figure 1. Molecular structures of the components: (a) polymerizable ionic liquids of MAImC1, MAImC8, and MAIm; (b) polyoxometalates of β-type octamolybdate (Mo8) and dodecatungstosilicate (SiW12) anions.
Figure 1. Molecular structures of the components: (a) polymerizable ionic liquids of MAImC1, MAImC8, and MAIm; (b) polyoxometalates of β-type octamolybdate (Mo8) and dodecatungstosilicate (SiW12) anions.
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Materials 12 02283 g002 550
Figure 2. IR spectra of Mo8 hybrid crystals: (a) as-prepared 1; (b) recrystallized 1; (c) as-prepared 2; (d) recrystallized 2.
Figure 2. IR spectra of Mo8 hybrid crystals: (a) as-prepared 1; (b) recrystallized 1; (c) as-prepared 2; (d) recrystallized 2.
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Materials 12 02283 g003 550
Figure 3. Crystal structures of Mo8 hybrid crystals (Na: green, C: gray, N: blue, O: red). Mo8 anions are represented by polyhedrons. H atoms are omitted for clarity; (a) packing diagram of 1 (left, along a axis) and molecular arrangement of the Mo8–Na+ 1D chain in 1 (right, along a axis); (b) packing diagram of 2 (left, along a axis) and molecular arrangement of Mo8-Na+ 1D chains in 2 (right, along c axis). A honeycomb-like arrangement of Mo8–Na+ 1D chains is highlighted by a light-blue broken hexagon; (c) molecular conformations of crystallographically independent MAImC8 cations in 2. C atoms relevant to the gauche conformation are numbered. Symmetry code: (i) 1 − x, −0.5 + y, 0.5 − z.
Figure 3. Crystal structures of Mo8 hybrid crystals (Na: green, C: gray, N: blue, O: red). Mo8 anions are represented by polyhedrons. H atoms are omitted for clarity; (a) packing diagram of 1 (left, along a axis) and molecular arrangement of the Mo8–Na+ 1D chain in 1 (right, along a axis); (b) packing diagram of 2 (left, along a axis) and molecular arrangement of Mo8-Na+ 1D chains in 2 (right, along c axis). A honeycomb-like arrangement of Mo8–Na+ 1D chains is highlighted by a light-blue broken hexagon; (c) molecular conformations of crystallographically independent MAImC8 cations in 2. C atoms relevant to the gauche conformation are numbered. Symmetry code: (i) 1 − x, −0.5 + y, 0.5 − z.
Materials 12 02283 g003
Materials 12 02283 g004 550
Figure 4. Powder XRD patterns of Mo8 hybrid crystals: (a) as-prepared 1; (b) calculated pattern of 1 using the structure obtained by single-crystal X-ray diffraction; (c) as-prepared 2; (d) calculated pattern of 2 using the structure obtained by single-crystal X-ray diffraction.
Figure 4. Powder XRD patterns of Mo8 hybrid crystals: (a) as-prepared 1; (b) calculated pattern of 1 using the structure obtained by single-crystal X-ray diffraction; (c) as-prepared 2; (d) calculated pattern of 2 using the structure obtained by single-crystal X-ray diffraction.
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Materials 12 02283 g005 550
Figure 5. IR spectra of Mo8 hybrid crystals: (a) as-prepared 3; (b) recrystallized 3; (c) as-prepared 4; (d) recrystallized 4.
Figure 5. IR spectra of Mo8 hybrid crystals: (a) as-prepared 3; (b) recrystallized 3; (c) as-prepared 4; (d) recrystallized 4.
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Materials 12 02283 g006 550
Figure 6. Crystal structures of SiW12 hybrid crystals (C: gray, N: blue, O: red). SiW12 anions are represented by polyhedrons. H atoms are omitted for clarity; (a) packing diagram of 3 (left, along a axis) and molecular arrangement of SiW12 anions in 3 (right, along b axis); (b) packing diagram of 4 (left, along c axis) and molecular arrangement of SiW12 anions in 4 (right, along a axis).
Figure 6. Crystal structures of SiW12 hybrid crystals (C: gray, N: blue, O: red). SiW12 anions are represented by polyhedrons. H atoms are omitted for clarity; (a) packing diagram of 3 (left, along a axis) and molecular arrangement of SiW12 anions in 3 (right, along b axis); (b) packing diagram of 4 (left, along c axis) and molecular arrangement of SiW12 anions in 4 (right, along a axis).
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Materials 12 02283 g007 550
Figure 7. Powder XRD patterns of SiW12 hybrid crystals: (a) as-prepared 3; (b) calculated pattern of 3 using the structure obtained by single-crystal X-ray diffraction; (c) as-prepared 4; (d) calculated pattern of 4 using the structure obtained by single-crystal X-ray diffraction.
Figure 7. Powder XRD patterns of SiW12 hybrid crystals: (a) as-prepared 3; (b) calculated pattern of 3 using the structure obtained by single-crystal X-ray diffraction; (c) as-prepared 4; (d) calculated pattern of 4 using the structure obtained by single-crystal X-ray diffraction.
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Table
Table 1. Crystallographic data of the hybrid crystals.
Table 1. Crystallographic data of the hybrid crystals.
Compound1234
Chemical formulaC27H39N6NaMo8O32C51H87N6NaMo8O33C40H60N8SiW12O50C72H107N8SiW12O51
Formula weight1750.142102.783687.224134.95
Crystal systemmonoclinicorthorhombicmonoclinicmonoclinic
Space groupI2/a (No. 15)P212121 (No. 19)P21/n (No. 14)P21/c (No. 14)
a (Å)13.6080(3)9.33330(10)14.8460(3)20.7451(16)
b (Å)17.6620(4)18.6205(2)12.6020(3)21.2737(6)
c (Å)21.8453(5)42.7175(5)19.6940(5)25.5199(8)
α (°)90.000090.000090.000090.0000
β (°)95.0422(14)90.000098.6520(10)103.067(5)
γ (°)90.000090.000090.000090.0000
V (Å3)5230.1(2)7423.90(14)3642.61(15)10970.9(10)
Z4424
ρcalcd (g cm−3)2.2221.8813.3612.503
T (K)100100100100
Wavelength (Å)0.800000.630000.600000.71075
μ (mm−1)2.7250.97612.04412.638
No. of reflections measured3512710228494446106869
No. of independent reflections5143157611451324752
Rint0.06000.08000.08700.1418
No. of parameters394883507644
R1 (I > 2σ(I))0.05530.05640.07210.0777
wR2 (all data)0.16800.15760.20460.2256

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Misawa, T.; Kobayashi, J.; Kiyota, Y.; Watanabe, M.; Ono, S.; Okamura, Y.; Koguchi, S.; Higuchi, M.; Nagase, Y.; Ito, T. Dimensional Control in Polyoxometalate Crystals Hybridized with Amphiphilic Polymerizable Ionic Liquids. Materials 2019, 12, 2283. https://doi.org/10.3390/ma12142283

AMA Style

Misawa T, Kobayashi J, Kiyota Y, Watanabe M, Ono S, Okamura Y, Koguchi S, Higuchi M, Nagase Y, Ito T. Dimensional Control in Polyoxometalate Crystals Hybridized with Amphiphilic Polymerizable Ionic Liquids. Materials. 2019; 12(14):2283. https://doi.org/10.3390/ma12142283

Chicago/Turabian Style

Misawa, Toshiyuki, Jun Kobayashi, Yoshiki Kiyota, Masayuki Watanabe, Seiji Ono, Yosuke Okamura, Shinichi Koguchi, Masashi Higuchi, Yu Nagase, and Takeru Ito. 2019. "Dimensional Control in Polyoxometalate Crystals Hybridized with Amphiphilic Polymerizable Ionic Liquids" Materials 12, no. 14: 2283. https://doi.org/10.3390/ma12142283

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