High‐T_c Enantiomeric Ferroelectrics Based on Homochiral Dabco‐derivatives (Dabco=1,4‐Diazabicyclo[2.2.2]octane)

Abstract

1,4‐Diazabicyclo[2.2.2]octane (dabco) and its derivatives have been extensively utilized as building units of excellent molecular ferroelectrics for decades. However, the homochiral dabco‐based ferroelectric remains a blank. Herein, by adding a methyl (Me) group accompanied by the introduction of homochirality to the [H2dabco]2+ in the non‐ferroelectric [H2dabco][TFSA]2 (TFSA=bis(trifluoromethylsulfonyl)ammonium), we successfully designed enantiomeric ferroelectrics [R and S‐2‐Me‐H2dabco][TFSA]2. The two enantiomers show two sequential phase transitions with transition temperature (Tc) as high as 405.8 K and 415.8 K, which is outstanding in both dabco‐based ferroelectrics and homochiral ferroelectrics. To our knowledge, [R and S‐2‐Me‐H2dabco][TFSA]2 are the first examples of dabco‐based homochiral ferroelectrics. This finding opens an avenue to construct dabco‐based homochiral ferroelectrics and will inspire the exploration of more eminent enantiomeric molecular ferroelectrics.

Tailoring the physical properties of hybrid magnetic quinuclidine-based plastic compoundsviaweak interactions

“…Especially interesting effects are due to homochirality, like in the case of ((R and S)-(+ −)-3˗Me-H 2 dabco)[TFSA] 2 (TFSA=bis(trifluoromethylsulfonylammonium)); homochiral ferroelectric compounds which show a large number of crystal phase transitions and a T c about 400 K higher than the one detected in [H 2 dabco][TFSA] 2 . 18 Other examples are the ((R)-(−)-3-hydroxyquinuclidium)[FeCl 4 ], 19 a plastic hybrid compound with chirality, ferroelectricity and long-range magnetic ordering, or ((R and S)-(+ −)-3-C 4 H 9 N))[CdCl 3 ] compound, a prirrolidine magnetic hybrid material with ferroelectric phase transition from C222 1 to P2 1 , with a significantly higher Curie temperature than the parent compound (C 4 H 10 N))[CdCl 3 ]. 20 Among these materials, those including paramagnetic ions give rise to magnetic hybrid materials, which are applied as components in many technologies, such as memory storage devices, electro-magnets or sensors.…”

Anions Distorting Triggering Ferroelectricity in a Molecular Crystal†

“…Most of the currently known molecular ferroelectric design strategies focus on selecting and modifying cations, such as H/F substitution, quasi‐spherical theory and introducing homochirality, etc . [ 29‐31 ] The sphere of cations with low rotational energy barriers is easily disordered at high temperatures and low order, which can create symmetry breaking. [ 32‐33 ] Then, by precise chemical modification of the cation, the probability of the crystal crystallising with the space group required for ferroelectricity can be greatly increased.…”

A lead bromide organic–inorganic hybrid perovskite material showing reversible dual phase transition and robust SHG switching

“…In recent years, quasi-spherical molecules such as 1,4-diazabicyclo[2.2.2]octane, quinuclidine and 1,5-diazabicyclo[3.2.1] octane have been widely used to synthesize multifunctional compounds with reversible phase transition, dielectric properties, second harmonic generation effects and ferroelectric properties. [32][33][34] This is because such molecules are easy to rotate at high temperature and form spherical structures in disorder, while they are in an orderly state at low temperature. Taking these considerations into account, designing and introducing suitable cations is an effective method to construct multifunctional perovskite compounds.…”