| Solid-state phase transition materials in the past decades have attracted increasing attention owing to their prospective applications in dielectric devices,nonlinear optical switches and ferroelectric random-access memories,etc.Recent progress in the research of solid-state phase transitions,associated with the reorientational motion of the flexible cations in the organic-inorganichybrids,has offered a potentially effective strategy in the exploration of novel phase transition materials.Some physical properties such as the dielectric constant are highly sensitive to the phase transition,thus the phase transition is usually accompanied by marked dielectric anomalies.Based on the research direction,cyclohexylmethylammonium,1,4-cyclohexanediammonium,protonated 1-methylimidazole and 4-aminotetrahydropyran were selected to react respectively with MX3?M=Sb,Bi;X=Cl,Br?by self-assembly reaction in solution,and 9 organic-inorganic hybrids containing cyclammonium were obtained,namely,[C7H16N]3·[BiBr5]·[Br]?1?,[C6H16N2]3·[BiBr5]2·[Br]2?2?,[C6H16N2]3·[SbBr5]2·[Br]2?3?,[C4H7N2]·[BiCl4]?4?,[C4H7N2]·[BiBr4]?5?,[C4H7N2]·[SbCl4]?6?,[C4H7N2]·[SbBr4]?7?,[C5H12NO]·[SbCl4]?8?and[C5H12NO]·[SbBr4]?9?.Single-crystal X-ray diffraction,IR spectroscopy,powder X-ray diffraction?PXRD?,and dielectric measurements were systematically conducted to investigate these 9compounds.It was suggested that 1 undergoes a structural phase transition at a high temperature up to 401.6 K,which is confirmed by combined DSC and variable-temperature PXRD measurements.Additionally,1 shows obvious step-like dielectric anomalies around 401.6 K,which are characteristics of switchable dielectrics.The results indicate that 1 could be regarded as phase transition material coupled with dielectric switching properties.For other 8 compounds,no obvious dielectric abnormal was observed,which may implies that these compounds experience no structural phase transitions within our measured temperature range.Besides,deep insights into the crystal structures of these compounds conclude that the organic cations have marked influence on the hydrogen bonds and the overall structure. |
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