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Comprehensive Summary: As an extended model of conventional molecular rotors, a conceived construction of novel crystalline molecular rotor that simultaneously contains two discrete polar rotators is presented here. The supramolecular self‐assembly of 18‐crown‐6 host and two rotator‐containing ion‐pair guests affords a three‐in‐one cocrystal, (2‐NH3‐iBuOH)(18‐crown‐6)[ZnBr3(H2O)], in which the hydroxyl group and aqua ligand both function as ultrasmall polar rotators. On the basis of the variable‐temperature single‐crystal X‐ray diffraction, variable‐temperature/frequency dielectric response, density functional theory calculations, and molecular dynamics simulations, it is found that such dual polar rotators experience a gradually enhanced rotation with increasing temperature, and more importantly, could be controlled by a reversible polar‐to‐polar structural phase transition, i.e., from a "single‐(polar rotator)" state at low‐temperature phase to a "mixed‐dual‐(polar rotator)" state in the vicinity of transition, and to an unusual "synchronized‐dual‐(polar rotator)" state at high‐temperature phase. [ABSTRACT FROM AUTHOR]

By utilizing a supramolecular complex rather than an individual molecule as a deformable and elastic substitutional component, we put forward a solid-solution strategy and demonstrate an example of how two related yet non-isostructural crystalline host–guest compounds can form molecular solid solutions. Interestingly, such a strategy can effectively and continuously modulate the molecular motion and phase transition in them, as revealed by the variable-temperature/frequency dielectric responses. [ABSTRACT FROM AUTHOR]

Abstract: Dielectric switches that can be converted between high and low dielectric states by thermal stimuli have attracted much interest owing to their many potential applications. Currently one main drawback for practical application lies in the non‐tunability of their switch temperatures (TS). We report here an ionic co‐crystal (Me3NH)4[Ni(NCS)6] that contains a multiply rotatable Me3NH+ ion and a solely rotatable one due to a more spacious supramolecular cage for the former one. This compound undergoes an isostructural order–disorder phase transition and it can function as a frequency‐tuned dielectric switch with highly adjustable TS, which is further revealed by the variable‐temperature structure analyses and molecular dynamics simulations. In addition, the distinct arrangements and molecular dynamics of two coexisting Me3NH+ ions confined in different lattice spaces as well as the notable offset effect on the promoting/hindering of dipolar reorientation after dielectric transition provide a rarely observed but fairly good model for understanding and modulating the dipole motion in crystalline environment. [ABSTRACT FROM AUTHOR]

The first thiocyanate-bridged double perovskite-type coordination polymer [NH4]2[NiCd(SCN)6] is reported here, which undergoes a reversible structural phase transition at around 120 K. An order–disorder mechanism for this transition is disclosed by X-ray structural analyses, dielectric measurement, as well as molecular dynamics simulations. [ABSTRACT FROM AUTHOR]

A new perovskite-like coordination polymer [(CH3)2NH2][Cd(N3)3] is reported which undergoes a reversible ferroelastic phase transition. This transition is due to varied modes of motion of the [(CH3)2NH2]+ guest accompanied by a synergistic deformation of the [Cd(N3)3]− framework. The unusual two-staged switchable dielectric relaxation reveals the molecular dynamics of the polar cation guest, which are well controlled by the variable confined space of the host framework. As the material switches from the ferroelastic phase to the paraelastic phase, a remarkable increase of the rotational energy barrier is detected. As a result, upon heating at low temperature, this compound shows a notable change from a low to a high dielectric state in the ferroelastic phase. This thermoresponsive host-guest system may serve as a model compound for the development of sensitive thermoresponsive dielectric materials and may be key to understanding and modulating molecular/ionic dynamics of guest molecules in confined space. [ABSTRACT FROM AUTHOR]

The first thiocyanate-bridged double perovskite-type coordination polymer [NH4]2[NiCd(SCN)6] is reported here, which undergoes a reversible structural phase transition at around 120 K. An order–disorder mechanism for this transition is disclosed by X-ray structural analyses, dielectric measurement, as well as molecular dynamics simulations. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: As an extended model of conventional molecular rotors, a conceived construction of novel crystalline molecular rotor that simultaneously contains two discrete polar rotators is presented here. The supramolecular self‐assembly of 18‐crown‐6 host and two rotator‐containing ion‐pair guests affords a three‐in‐one cocrystal, (2‐NH3‐iBuOH)(18‐crown‐6)[ZnBr3(H2O)], in which the hydroxyl group and aqua ligand both function as ultrasmall polar rotators. On the basis of the variable‐temperature single‐crystal X‐ray diffraction, variable‐temperature/frequency dielectric response, density functional theory calculations, and molecular dynamics simulations, it is found that such dual polar rotators experience a gradually enhanced rotation with increasing temperature, and more importantly, could be controlled by a reversible polar‐to‐polar structural phase transition, i.e., from a "single‐(polar rotator)" state at low‐temperature phase to a "mixed‐dual‐(polar rotator)" state in the vicinity of transition, and to an unusual "synchronized‐dual‐(polar rotator)" state at high‐temperature phase. [ABSTRACT FROM AUTHOR]

Block-shaped single crystals of the new title compound are synthesized by slow evaporation of the filtrate of an aqueous mixture of Cd(NO3)2, NaN3, and Me4NBr in the ratio of 1:12:6 (20 °C, 55% yield). [ABSTRACT FROM AUTHOR]