Tadpole-Like Polar Molecule Encapsulated in a Two-in-One Supramolecular Cage: Molecular Motion, Phase Transition and Ferroelectricity

Molecule-inclusive closed cage compounds present a unique platform for molecular motion in an isolated environment. This study showcases the incorporation of a tadpole-like polar molecule (1-propyl-1H-imidazole, PIm) into a supramolecular cage formed by duad semicage p-tert-butylcalix[4]arene. The ferroelectric phase transition as well as the cage-confined motion of encapsulated PIm was studied in detail. The unusual quadrastable state of the PIm in the paraelectric phase allows for the modulation of dipolar polarization over a broad temperature/frequency range. This compound represents the first example of a clathrate molecular ferroelectric featuring a molecule-inclusive supramolecular cage, and it also contributes to the understanding of cage-confined molecular dynamics.