A multifunctional molecular ferroelectric with a high Curie temperature and electrical–thermal double-switch coexistence: (C8H14NO)[FeCl4]

Abstract

Quasi-spherical molecules are used to construct high-performance molecular ferroelectrics, but accurately producing polar crystals with low symmetry remains a challenge. Herein, we report a novel high-temperature multiaxial molecular ferroelectric (C₈H₁₄NO)[FeCl₄] (1) (C₈H₁₄NO = 1-methyl-3-quininocyclone). Dielectric and differential scanning calorimetry (DSC) measurements showed that compound 1 had a high Curie temperature of 341.8 K. It crystallizes in the Cmc2₁ space group at room temperature, showing switchable SHG response, moderate spontaneous polarization (P_s = 0.24 μC cm⁻²), and clear ferroelectric domains. In addition, DSC and dielectric cycling tests indicate that compound 1 can be used as an excellent electric double-switch material. Notably, the distinct symmetry breaking, that is, 4/mmmFmm2, leads to a biaxial ferroelectric with four equivalent directions of polarization. This discovery provides an effective approach for constructing multiaxial high-temperature molecular ferroelectrics.