Theoretical Estimation of Important Ferroelectricity-Related Parameters for Molecular Design of Host–Guest Compounds, Substituted Anilinium Tetrafluoroborate 18-Crown-6

Abstract

Through rational chemical modification, a series of host–guest complexes, substituted anilinium tetrafluoroborate 18-crown-6, are constructed to achieve excellent ferroelectricity in terms of large spontaneous polarization, high phase transition temperature, and small coercive field. In order to evaluate our new design, computational methods are developed to estimate the ferroelectricity-related parameters, namely, spontaneous polarization, phase transition temperature, and coercive field, in sufficient consideration of structural and symmetrical characteristics of this series of host–guest complexes at the molecular level. In each host–guest crystal, the substituted anilinium acts as a rotator anchoring in the cavity of a stator, 18-crown-6, with three N–H···O hydrogen bonds. This rotator does the pendulum motion of the phenyl ring with its substituent to switch ferroelectric-paraelectric phase transition. High-accuracy quantum chemistry calculations are carried out to obtain complete energy and polarization information along this pendulum-motion-related reaction coordinate. Then the Landau–Devonshire phase transition theory and the Boltzmann statistics are employed to create a bridge between the above ferroelectric molecular behavior and the crystalline macroscopic properties and estimate the phase transition temperatures of these studied host–guest complexes. By virtue of applying an external electric field in our quantum chemistry calculations, the relative magnitude of the coercive field is approximately measured to exhibit the electric-field-responsive behavior of these host–guest self-assemblies. Finally, two candidates, namely, (4-CN-Ani+)­(18-crown-6)­BF4 – and (4-CHO-Ani+)­(18-crown-6)­BF4 –, are designed by us with large excellent ferroelectricity compared to the model system (4-MeO-Ani+)­(18-crown-6)­BF4 –. They would wait for the future experimental confirmation. Our molecular design of these ammonium-crown ether-based host–guest compounds would provide insights into the structure–property relationship of these rotator-stator-type ferroelectrics to help both theoretical and experimental specialists design or/and synthesize new targeted compounds. Our developed computational methods to estimate ferroelectricity-related parameters would also supply ideas for computational scientists to produce new similar methods for some ferroelectrics with specific phase-transition-related molecular dynamics.

The past 10 years of molecular ferroelectrics: structures, design, and properties

“…67 Similarly, [(4-CN-PhNH 3 )(18-crown-6)][BF 4 ] and [(4-CHO-PhNH 3 )(18-crown-6)][BF 4 ], two analogous candidates, were designed and estimated theoretically with excellent ferroelectricity compared to the model system. 75 To improve the T c of the host–guest supramolecules, the larger and heavier bis(trifluoromethanesulfonyl)ammonium (TFSA) was introduced as the anion, which brings a lower crystal symmetry at RT and a higher energy barrier of molecular motions in the phase transition, endowing [(C 7 H 10 NO)(18-crown-6)][TFSA] with multiaxial ferroelectricity and a high T c up to 415 K. 68 A wide working temperature range for a variety of applications is made possible by the record temperature improvement in reported crown-ether-based ferroelectrics.…”

2-Chloroethylamine·trifluoromethanesulfonate combined with 18-crown-6: a ferroelectric with excellent dielectric switching properties

“…19,20 In particular, 18-crown ether-6-based inclusions are often used as a platform for the construction of molecular ferroelectric and piezoelectric materials, as the host–guest inclusions may have ordered–disordered phase transitions. 21–24 Xiong et al have successfully designed a high-temperature multiaxial host–guest inclusion ferroelectric [(MeO-C 6 H 4 -NH 3 )(18-crown-6)][TFSA] (MeO-C 6 H 4 -NH 3 = 4-methoxyanilinium, TFSA = bis(trifluoromethanesulfonyl)ammonium) by adjusting the anion to control the “momentum matching” in the crystal structure. The internal environment of the crystal has changed and a new and distinct interaction between (MeO-C 6 H 4 -NH 3 ) + and the TFSA anion has taken place.…”

The Synthesis, Structure, and Dielectric Properties of a One-Dimensional Hydrogen-Bonded DL-α-Phenylglycine Supramolecular Crown-Ether-Based Inclusion Compound

“…Host-guest crown-ether-based supramolecular structures, represented by organic amines and crown ethers, are prone to molecular rocking, proton transfers, and order-disorder transitions within the structural units of hybrid materials via intermolecular forces, hydrogen bonds, and other interactions. Therefore, these supramolecular structures have important applications in photoelectric conversion, storage devices, capacitors, and sensors [34][35][36][37][38][39][40][41][42][43][44]. The research group headed by Professor Xiong at Southeast University [45] successfully synthesized a high-temperature multi-axial host-guest inclusion ferroelectric material that undergoes phase transitions [(MeO-C 6 H 4 -NH 3 )(18-crown-6)][TFSA].…”