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.