Ferroelastic phase transition and switchable dielectric behavior associated with ordering of molecular motion in a perovskite-like architectured supramolecular cocrystal†
Abstract
An organic supramolecular co-crystal with a perovskite-like architecture, dabco·p-nitrophenol (1, dabco = at around 128 K (Tc), displays switchable dielectric behaviors triggered by the ordering of molecular rotational motion in the dabco moieties. Its transition dynamic behaviors were investigated by variable-temperature crystal structure analysis, thermal analysis and dielectric measurements. The results reveal that in the high-temperature state, 1 behaves as a molecular rotor, in which the dabco moiety rotates around the N⋯N axis as a rotator, and the neutral p-nitrophenol part acts as a stator jointed through the intermolecular N–H⋯O H-bonds. Below the Tc, the rotational motions of the rotator are frozen and the whole setup becomes much more ordered, corresponding to its low-temperature stable phase. Moreover, study of the deuterated analogue of 1 excludes the possibility of