Dielectric Phase Transition Induced by Halogen Substitution Based on 1,4-Diazabicyclo[2.2.2]octane-Derivatives

We successfully synthesized (X-EtHDabco)[ZnBr4] (X=H, F, Cl for compound 1, 2, and 3, EtDabco=N-ethyl-1,4-diazoniabicyclo[2.2.2]octane) through precise molecular design. Systematic measurements (powder X-ray diffraction, differential scanning calorimetry measurements, dielectric measurements) were performed on these compounds. It is noteworthy that, no hint of heat anomaly was observed for 1, while both 2 and 3 displayed intriguing isostructural order-disorder phase transition near 230 K. Through the analysis of the crystal structure, the order-disorder transformation of organic ammonium plays a major role in the phase transition, in addition, the displacement of the inorganic framework also contributes to dielectric response.

Automated summary

Three compounds were successfully synthesized through precise molecular design, and systematic measurements were conducted on them. It was found that two of the compounds displayed intriguing isostructural order-disorder phase transition near 230 K, with the order-disorder transformation of organic ammonium playing a major role in the phase transition.