Molecular Motions and Hydrogen-Bonding Networks in (o-Aminoanilinium)–(Crown Ethers)–[PMo12O40]4− Crystals

Abstract

Single crystals formed from hydrogen-bonding supramolecular cations of o-aminoanilinium (HOPD +)crown ethers, (HOPD +)([12]crown-4), (HOPD +)([15]crown-5), and (HOPD +)([18]crown-6), and one-electron-reduced [PMo 12 O 40 ] 4¹ Keggin-type clusters were synthesized. The crystal structures and dielectric responses of the three new compounds (HOPD +) 4 ([12]crown-4) 4 [PMo 12 O 40 ] 4¹ ¢4CH 3 CN (1), (HOPD +) 4 ([15]crown-5) 4 [PMo 12 O 40 ] 4¹ (2), and (HOPD +) 4 ([18]crown-6) 4 [PMo 12 O 40 ] 4¹ ¢8CH 3 CN (3) were examined. The CH 3 CN molecules in salts 1 and 3 were included in zero-dimensional pores and one-dimensional channels, respectively; higher thermal stability was observed in the former lattice because of its extended hydrogen-bonding network. Large frequencyand temperature-dependent dielectric responses were confirmed in salts 2 and 3, whereas the dielectric response of salt 1 was quite small. The fixed orientation of HOPD + because of the hydrogen-bonding network was consistent with the dielectric property of salt 1. In contrast, large magnitudes of dielectric responses in the temperature range above 280 K were observed for salt 3. Thermal motions of CH 3 CN molecules in the channel were the origin of such dielectric responses. In salt 2, the thermally activated coupled motion of the orthogonally arranged HOPD + pair along the CNH 3 +-axis with the potential energy barrier of ca. 80 kJ mol ¹1 resulted in large dielectric responses.

Self-assembled Structure of Inorganic–Organic Hybrid Crystals Based on Keggin Polyoxometallates [SMo12O402–] and Supramolecular Cations

“…Hydrogen bonding can be modified by choosing reasonable and distributing functional groups such as −COOH, −NH 2 , and −OH in the molecular systems. Recently, anilinium derivatives were used to replace the H 3 O + ion of oxonium-crown and of constructed supramolecular cations that were introduced into POMs. , Many inorganic–organic hybrids based on POMs and supramolecular cations have been successfully obtained because of the advantages of supramolecular cations, namely (a) numerous hydrogen bonding sites that can effectively combine with POMs in the solid state; (b) a relatively large size, comparable to that of Keggin anions, which is suitable for constructing stable crystals; and (c) their size and charge can be modified by changing anilinium and crown ether derivatives, which can affect the electrostatic interaction with POM anions. Our laboratory reported the synthesis of some of the inorganic–organic hybrids based on supramolecular cations and Keggin [PMo 12 O 40 n – ], and the structural characteristics of supramolecular cations and the packing diagrams of POMs were discussed.…”

Two Supramolecular Inorganic–Organic Hybrid Crystals Based on Keggin Polyoxometalates and Crown Ethers

“…The typical organic cations are tetrathiafulvalene and ferrocenyl derivatives [21][22][23][24][25]. Recently, the Nakamura group used large-sized crown ethers as organic building blocks and designed supramolecular inorganic-organic hybrids with POMs [26][27][28]. Crown ethers are excellent supramolecular building blocks due to their structural advantages.…”

A proton transfer and a cobalt(II) compound including 2,6-pyridinedicarboxylate and o-phenylenediamine ions: Synthesis, characterization, crystal structure and solution study

“…In this regard, a large number of proton transfer compounds have been constructed with o-phenylenediamine (OPD) acting as the proton acceptor with different acids such as chloroacetic acid [15], benzoic acid [16], malonic acid [17], phosphorous acid [18], and picric acid [19] as the proton donors. OPD can coordinate with the metal center as a unidentate in a cationic form [20], as a chelate in a neutral form [21][22][23][24], as well as a bridge between two metal atoms through amine groups [25], and it can be also found in some complexes as a discrete cation [26].…”