Crystal Structure, Phase Transition and Dielectric Behaviors of One-dimensional Organic-inorganic Bromoargentate Hybrids of [Et-dabco]2Ag2Br4

Abstract

A new haloargentate hybrid, [Et-dabco]₂Ag₂Br₄ (1) (Et-dabco⁺=1-Ethyl-1,4-diazabicyclo[2.2.2]octan-1-ium), has been successfully synthesized by a solution diffusion method and characterized using microanalysis, single crystal X-ray diffraction, variable-temperature powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC), and dielectric spectra. The crystal structure of 1 at 273 K contains one-dimensional (1D) anionic [Ag₂Br₄]²⁻ chains, with the [Et-dabco]⁺ cations embedded in the gaps between the inorganic chains. Hybrid 1 underwent a reversible structural phase transition (SPT) at around 464.5 K on heating, and the Pawley refinement revealed similar crystal structures in the low- and high-temperature phases. The SPT endows 1 with switchable and bistable dielectric properties. Combined with previous studies, it was revealed that the self-assembly of silver halide (AgX) with the lower rotational energy barrier of 1-alkyl-1,4-diazabicyclo[2.2.2]octan-1-ium in solution probably achieves new phase transition materials.