Organic enantiomeric high-T c ferroelectrics.
Peng-Fei LiWei-Qiang LiaoYuan-Yuan TangWencheng QiaoDewei ZhaoYong AiYe-Feng YaoRen-Gen XiongPublished in: Proceedings of the National Academy of Sciences of the United States of America (2019)
For nearly 100 y, homochiral ferroelectrics were basically multicomponent simple organic amine salts and metal coordination compounds. Single-component homochiral organic ferroelectric crystals with high-Curie temperature (T c) phase transition were very rarely reported, although the first ferroelectric Rochelle salt discovered in 1920 is a homochiral metal coordination compound. Here, we report a pair of single-component organic enantiomorphic ferroelectrics, (R)-3-quinuclidinol and (S)-3-quinuclidinol, as well as the racemic mixture (Rac)-3-quinuclidinol. The homochiral (R)- and (S)-3-quinuclidinol crystallize in the enantiomorphic-polar point group 6 (C 6) at room temperature, showing mirror-image relationships in vibrational circular dichroism spectra and crystal structure. Both enantiomers exhibit 622F6-type ferroelectric phase transition with as high as 400 K [above that of BaTiO3 (T c = 381 K)], showing very similar ferroelectricity and related properties, including sharp step-like dielectric anomaly from 5 to 17, high saturation polarization (7 μC/cm2), low coercive field (15 kV/cm), and identical ferroelectric domains. Their racemic mixture (Rac)-3-quinuclidinol, however, adopts a centrosymmetric point group 2/m (C 2h), undergoing a nonferroelectric high-temperature phase transition. This finding reveals the enormous benefits of homochirality in designing high-T c ferroelectrics, and sheds light on exploring homochiral ferroelectrics with great application.