An Order–Disorder Ferroelectric Host–Guest Inclusion Compound

The host–guest complex (DIPA)(18]crown‐6)](ClO₄) ( 1 ; DIPA=2,6‐diisopropylanilinium) was constructed and found to undergo a sequence of phase transitions (Ibam–Pbcn–Pna2₁) at T₁=278 K and T₂=132 K, respectively. Systematic characterizations, such as differential scanning calorimetry, heat capacity, temperature‐dependent dielectric constant, and P–E hysteresis loop, reveal that the centrosymmetric‐to‐polar phase transition at T₂ is a paraelectric‐to‐ferroelectric transition. The symmetry breaking was also confirmed by temperature‐dependent second‐harmonic generation effect and X‐ray powder diffraction. The ferroelectric mechanism is attributable to the linear motion of the perchlorate counterions accompanied by the order–disorder transition of the 18]crown‐6 molecules and the anions.