Potential Multiaxial Molecular Ferroelectricity through Chiral Cation Replacement

Molecular ferroelectrics are an important class of materials offering chemical versatility, low toxicity, and tunable functional properties. A major design challenge lies in achieving multiaxial properties akin to inorganic perovskite ferroelectrics. Here, we report a series of new potential multiaxial molecular ferroelectrics obtained by introducing chiral cations into a structure type known to undergo a phase transition that raises the symmetry significantly. Three of the compounds studied show an Aizu m3̅mFm phase transition, resulting in 24 equiv polarization directions in the polar phase. ¹H solid-state NMR was used to study the dynamics of the organic cation, confirming rapid rotation about the 3-fold rotation axis of the cubic cell. This blurs the chiral center to an X-ray probe, making the distinction between Sohncke and non-Sohncke space group choices redundant.

Chiral cation incorporation reveals a new family of potential multiaxial molecular ferroelectrics. Solid-state NMR shows the dynamic disorder of the cation, rendering crystallographic chirality indistinct to X-ray diffraction.