Plastic crystals show diverse functional properties, for example, resemblance to a liquid with internal rotation degrees of freedom, the colossal barocaloric effect (BCE), excellent ion conduction, huge enthalpy changes between phase transition of the crystal and plastic crystal, and so forth. These unique natures endow plastic crystals with a range of applications in the material areas of the BCE and solid-state thermal energy storage, solid electrolytes, and solid-state “solvent” for ion doping. Herein, we present the study of DSC, temperature-dependent powder X-ray diffraction, and ion conduction for an organic ion plastic crystal, TBA2[Ni­(mnt)2] (1; TBA+ = tetra-n-butylammonium, mnt2– = maleonitriledithiolate). Upon heating, 1 undergoes a crystal-to-plastic crystal transition at ∼398 K and a plastic crystal-to-plastic crystal transformation at ∼415 K. The annealing process cooled from the plastic crystal state induces a series of reversible solid–solid phase transitions, related to the conformation transformation of alkyl chains in cations; amongst them, an exothermic solid–solid phase transition occurs at ∼324 K, releasing huge latent heat during heating process, which is in contrast to most observations, and such a material releasing large latent heat near room temperature has promising application in thermal energy storage. Additionally, two plastic crystal phases in 1 extend from 398 to 473 K at least (1 starts to decompose around 500 K), with a wide temperature window and high ion conductivity of 10–3 to 10–2 S·cm–1, indicating that 1 is a good ion conductor.

The emerging organic ion plastic crystals (OIPCs) are the most promising candidates used as solid-state electrolytes in a range of ionic devices. To endow an OIPC with additional functionality may create a new type of material for multifunctional devices. Herein, we present an ion plastic crystal, [EMIm]­[Ni­(mnt)2] (1; [EMIm]+ = 1-ethyl-3-methylimidazolium and mnt2– = maleonitriledithiolate), and its crystal consists of twin dimeric chains of [Ni­(mnt)2]− anions, embraced by [EMIm]+ cations. A crystal-to-plastic crystal transformation with a large latent heat that occurred at ∼367/337 K on heating/cooling is confirmed by the differential scanning calorimetry (DSC) technique. The plastic crystal phase in 1, characterized by variable temperature powder X-ray diffraction (PXRD) and optical microscopy images, spans a broad temperature range with ΔT ∼123/153 K on heating/cooling (DSC measurement), and the wide ΔT is relevant to an extra stable anion chain owing to the strong antiferromagnetic (AFM) interactions protecting the chain from collapse in the plastic crystal state. 1 is a single-component ion plastic crystal with a record high ion conductivity, 0.21 S·cm–1, at 453 K. The crystal-to-plastic crystal transformation in 1 is coupled to a bistable magnetic transition to give a multi-in-one multifunctional material. This study provides a creative thought for the design of OIPCs with striking thermal, electrical, and magnetic multifunctionality.

Organic ion plastic crystals (OIPCs) show promising applications in various all- solid-state electrochemical energy storage devices. In this regard, superionic conducting OIPCs with broad temperature window are highly demanded. Herein,...

A thermochromic or mechanochromic material can switch between at least two stable states in response to changes in temperature or static pressure/strain. In this study, we investigated a Ni-dithiolene dianion...

The phase transition materials, with abrupt change of electrical, magnetic, or optical responses in the phase transition vicinity, may have applications in data storage, signal processing, and switchable devices. Herein, we present the study of structural, magnetic, dielectric, and thermal properties for an S = 1/2 magnetic chain system, [DMPy][Ni(mnt) 2 ] (1; DMPy + = N-dimethyl pyrrolidinium and mnt 2− = maleonitriledithiolate). Two ongoing magnetostructural transitions appear at ∼270 and ∼307 K, giving low-(LTP), intermediate-(ITP), and high-temperature (HTP) phases of 1. LTP crystallizes in P2 1 /c, while both ITP and HTP belong to Pnma space group. The LTP−ITP phase transition is broken symmetry associated with one-dimensional (1D) regular magnetic chain dimerization, the spin gap opened in LTP, and no visible latent heat, showing the typical character of the second-order spin-Peierls transition. The ITP−HTP transformation is an isostructural phase transition, which is coupled with the sharp change of the cation orientation, accompanied by latent heat and dielectric anomaly, with the typical character of the first-order phase transition. This study demonstrates the coexistence of diverse mechanisms of magnetostructural phase transition in an 1D radical salt and opens a way for design and preparation of new switchable magnetic and electric materials.