Tunable and Switchable Dielectric Constant in an Amphidynamic Crystal

The inclusion compound [(CH3)2­NH2]2­[KCo­(CN)6] exhibits a marked temperature-dependent dielectric constant and can be considered as a model of tunable and switchable dielectric materials. Crystal structure and solid-state NMR studies reveal a switchable property between low and high dielectric states around 245 K. This originates from an order–disorder phase transition of the system, changing the dynamics of the polar dimethylammonium (DMA) cation. Furthermore, the tuning of the dielectric constant at temperatures below the phase transition point is related to increasing angular pretransitional fluctuations of the dipole moment of DMA.包合物[(CH₃)₂NH₂]₂[KCo(CN)₆]展现出显著的温度依赖性介电常数，可作为可调谐与可切换介电材料的模型体系。晶体结构与固态核磁共振（solid-state NMR）研究表明，该体系在约245 K附近存在低介电态与高介电态之间的可切换特性。这一特性源于体系的有序-无序相变，该相变改变了极性二甲基铵（DMA）阳离子的动力学行为。此外，在相变温度以下区域介电常数的可调谐性，与DMA偶极矩逐渐增强的角向预转变涨落密切相关。