Designing and Constructing a High‐Temperature Molecular Ferroelectric by Anion and Cation Replacement in a Simple Crown Ether Clathrate

Abstract

Molecular ferroelectrics have displayed ap romising future since they are light-weight, flexible, environmentally friendly and easily synthesized,c ompared to traditional inorganic ferroelectrics. However, how to precisely design a molecular ferroelectric from an on-ferroelectric phase transition molecular system is stillagreat challenge. Here we designed and constructed am olecular ferroelectric by double regulation of the anion andc ation in as imple crown ether clathrate, 4,[ K(18-crown-6)] + [PF 6 ] À .B yr eplacing K + and PF 6 À with H 3 O + and [FeCl 4 ] À respectively,w eo btained an ew molecular ferroelectric [H 3 O(18-crown-6)] + [FeCl 4 ] À , 1.C ompound 1 undergoes a para-ferroelectricp hase transition near 350 Kw ith symmetry change from P21/n to the Pmc21 space group. X-ray single-crystal diffraction analysis suggests that the phase transition was mainly triggered by the displacementm otion of H 3 O + and[ FeCl 4 ] À ions and twist motion of 18-crown-6m olecule. Strikingly,c ompound 1 shows high aC urie temperature (350 K), ultra-strong second harmonic generation signals (nearly 8t imes of KDP), remarkable dielectric switching effect and large spontaneous polarization. We believe that this research will pave the way to design and build high-quality molecular ferroelectrics as well as their application in smart materials.

Coupling Narrow Band Gap and Switchable SHG Responses in a New Molecule Ferroelectric: Imidazolyl Propylamine Pentabromo Stibium(III)

“…For a ferroelectric, the essential mark is to judge whether it has a perfect hysteresis loop, since a hysteresis loop is the most important parameter to characterize a ferroelectric. , The ferroelectricity and polarizability of compound 1 are obtained through the polarization–electric hysteresis loop ( P - E ) test. As shown in Figure , the typical rectangular P-E hysteresis loop obtained at different temperatures affords evidence for the ferroelectric properties of compound 1 by using the Sawyer–Tower circuit method.…”

Crown Ether Host‐Guest Molecular Ferroelectrics

“…Due to the poor diffraction data in PP, variable-temperature PXRD measurements were employed (Figure 9c). The significant reduction of the number of PXRD patterns from FP to PP shows 12), [23] satisfying the polar crystal symmetry for ferroelectrics. The crystal structure of 12 is isostructural to that of 11 (Figure 10a).…”

“…Zhou et al. then replaced the counterion [PF 6 ] − with [FeCl 4 ] − , and the crystal symmetry changes to the polar Pmc 2 1 in [H 3 O(18‐crown‐6)][FeCl 4 ] ( 12 ), [23] satisfying the polar crystal symmetry for ferroelectrics. The crystal structure of 12 is isostructural to that of 11 (Figure 10a).…”

“…[15][16][17][18] A series of crown ether molecular ferroelectrics with organic ammonium cations, hydrated cations and metal cations have been discovered. [15][16][17][18][19][20][21][22][23][24][25] For example, Fu et al anchored the 4-methoxyaninium the crown ether to construct a host-guest ferroelectric [(4-methoxyaninium)(18-crown-6)][BF 4 ] with phase transition point of 127 K. [15] The ferroelectricity is derived from the order-disorder transition of the gust 4methoxyaninium cation. By using a similar organic cation DIPA (DIPA = 2,6-diisopropylanilinium), a new crown-ether-based molecular ferroelectric [(DIPA)(18-crown-6)][ClO 4 ] has been constructed.…”

“…The structure makes the components prone to occur order‐disorder transition easily, which is beneficial for inducing ferroelectric phase transitions [15–18] . A series of crown ether molecular ferroelectrics with organic ammonium cations, hydrated cations and metal cations have been discovered [15–25] . For example, Fu et al.…”