New Organic Ferroelectrics: Cocrystal of 5,5′-Dimethyl-2,2′-bipyridine and Bromanilic Acid

Abstract

Cocrystal 55DMBPH 2 ba was synthesized and characterized. The crystal structure is isostructural to cocrystal 55DMBP H 2 ia with iodanilic acid. The heat capacity, dielectric permittivity, and polarizationelectric field hysteresis showed that the 55DMBPH 2 ba undergoes a paraelectricferroelectic phase transition at 253 K on cooling. The transition mechanism is discussed through the analysis of isotropic temperature factors of atoms.Recently, organic ferroelectrics having a hydrogen bond (H bond), e.g., phenazinechrolanilic acid 1 (PhzH 2 ca), have been paid increasing attention.2,3 In those compounds, dielectric properties depend on a combination of H-bond donor and acceptor.2 A representative series is cocrystals between 5,5¤-dimethyl-2,2¤-bipyridine (55DMBP) and H 2 xa: 55DMBPH 2 ca is antiferroelectric 4 whereas 55DMBPH 2 ia (iodanilic acid) ferroelectic.5 Since both ferroelectricity and antiferroelectricity are found, the series is very important for understanding the mechanism that determines the dielectric nature of such organic complexes. However, there has been no report on 55DMBP H 2 ba (bromanilic acid) so far. In this letter, we report its synthesis, structure, and properties.Single crystals of 55DMBPH 2 ba were grown by diffusion using dehydrated acetone (Wako, >99.5%) as a solvent. Commercial 55DMBP (Aldrich, 98%) and H 2 ba (TCI, >98%) were purified by fractional sublimation in vacuum before dissolving them in dehydrated acetone. The growth took about 2 months. The yield was very low (15%) even in successful cases. Due to the difficulty in crystal growth, only a limited number of single crystals were available for measurements of physical properties. This prevented the authors from performing precise characterization at the highest level.Structure analyses were performed using a SMART APEX diffractometer (Bruker AXS KK). Data collections were performed at room temperature (295 K) and 200 K. Unit-cell refinement and data reduction were carried out using SAINT.

Coexistence of normal and inverse deuterium isotope effects in a phase-transition sequence of organic ferroelectrics

“…2b ). Compared with an earlier report, 34 in our reexamination, the peak value of ε r was significantly improved to a value of 13 000. H55dmbp-Hba, as well as H55dmbp-Hia and H22bpy-Hia, exhibited a huge Curie–Weiss constant ( Table 1 ), which is about two orders of magnitude larger than T c .…”

“…The 1 : 1 cocrystal of 2,2 0 -bipyridine (22bpy) and iodanilic acid (H 2 ia) is a new compound that crystallizes as a proton-transferred monovalent salt. As reference compounds for our study we chose two compounds with similar crystal structures; these were cocrystals of 5,5 0 -dimethyl-2,2 0 -bipyridine (H55dmbp) with Hia 28 and with Hba, 34 the ferroelectricity of which has been reported independently. All these single crystals can be satisfactorily grown through slow evaporation of solutions in methanol, and they comprise linear supramolecular chains of alternating acid and base molecules, as demonstrated below.…”

Soft Ferroelectrics Enabling High‐Performance Intelligent Photo Electronics

“…Dipole re-arrangement via proton tautomerization and noncentrosymmetry similar to those observed in single component small molecules is also found in soft ferroelectrics based on supramolecular assembly. [54][55][56][57][58][59][60][61][62][63][64][65] In supramolecular systems, hydrogen bondings occur between two different molecules, causing inner polarization with proton tautomerization. The dipole arrangement renders a centrosymmetry in the assembly showing paraelectric properties offset.…”

Superspace approach helps: determination of proton dynamics in the phase transition of modulated supramolecular ferroelectrics: 5,5′-dimethyl-2,2′-bipyridine and bromanilic acid

“…They have been co-crystallized with different base molecules, e.g. phenazine [10][11][12][13] and bipyridines, [14][15][16] which accommodate two symmetrically arranged nitrogen atoms that may accept protons. Switchable polar structures are designed by alternating these acid and base molecules along an extended chain through intermolecular O-H⋯N hydrogen bonds.…”