Coexistence of Magnetic-Optic-Electric Triple Switching and Thermal Energy Storage in a Multifunctional Plastic Crystal of Trimethylchloromethyl Ammonium Tetrachloroferrate(III).

Driven by the rapidly increasing demand for technological applications, multifunctional materials have been one important research area, which are expected to enhance the capacity and versatility of materials in various applications. Nevertheless, combining more than three functions in one molecular compound is still a challenge. Molecular solid-solid phase transition materials could exhibit switchable properties, which could have potential applications such as switches, sensors, and memory devices. However, these switchable molecular materials are rarely researched as thermal energy storage materials. In this work, we report the coexistence of thermal energy storage and magnetic-optic-electric triple switching in a plastic crystal, trimethylchloromethyl ammonium tetrachloroferrate(III), ([(CH3)3NCH2Cl][FeCl4], referred to as 1). 1 undergoes plastic phase transition at near room temperature (326 K) induced by the order-disorder of the ions. The magnetic-optic-electric triple switching in 1 could be triggered by temperature stimuli near room temperature. Meanwhile, with utilization of large latent heat during the phase transition process and sensible heat, the energy storage in 1 is up to 107 J g-1 from 293 to 343 K, demonstrating its thermal energy storage application in solar energy systems and industrial sectors. This work particularly exhibits the advantages of plastic molecular materials as thermal energy storage materials and introduces the thermal energy storage into the multi-switchable plastic phase transition molecular materials, which will give extra flexibility for the design of new types of multifunctional materials.