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. [ABSTRACT FROM AUTHOR]