A new crown-ether clathrate [15-crown-5][Y(NO3)2(H2O)5][NO3] with switchable dielectric constant behaviour

Abstract

Molecule-based switchable dielectrics with distinct changes of dielectric constant, which enable conversion of electronic properties between different states under external stimuli, are technologically important. The crown-ether clathrate system is a highly promising class of molecule-based switchable dielectrics. Herein, by choosing yttrium nitrate to be assembled with a 15-crown-5 molecule, we synthesized a new crown-ether clathrate, namely [15-crown-5][Y(NO₃)₂(H₂O)₅][NO₃] (1). One relatively small thermal anomaly peak was observed centered at 230 K (T_tr) for compound 1. Single-crystal structures obtained at various temperatures revealed its reversible phase transition to be driven by the synergistic effect of the dynamic changes of the counter [NO₃]⁻ anions from an ordered to disordered state and the relatively strong thermal vibrations of the 15-crown-5 molecules, along with the rearrangement of [Y(NO₃)₂(H₂O)₅]⁺ cations in the crystal. Meanwhile, compound 1 also displayed a bistable dielectric response characteristically found in different structural phases. This discovery confirmed the possibility of using compound 1 as a molecule-based dielectric switching material.