Synchronous Switching of Dielectric Constant and Photoluminescence in Cyanidonitridorhenate‐Based Crystals

Switching of multiple physical properties by external stimuli in dynamic materials opens the applications in, e.g., smart sensors, biomedical tools, as well as data storage devices. Among stimuli‐responsive materials, inorganic‐organic molecular hybrids exhibiting thermal order‐disorder phase transitions were tested as promising molecular switches of electrical characteristics, including dielectric constant. We aimed at broadening the multifunctional potential of such hybrid materials towards the switching of not only electrical but also other physical properties, e.g., light emission. We report two ionic salts based on luminescent tetracyanidonitro‐rhenate(V) anions bearing two different diamine ligands, 1,2‐diaminoethane (1) and 1,3‐diaminopropane (2), both crystallizing with polar N‐methyl‐dabconium cations. They exhibit the order‐disorder phase transition related to the heating‐induced turning on of the rotation of polar cations. This leads to the unique synchronous switching of dielectric constant, as well as metal‐complex‐centered photoluminescence, as demonstrated by changes in, e.g., emission lifetime. The roles of organic cations, non‐trivial Re(V) complexes, and their interaction, in achieving the coupled thermal switching of electrical and optical properties are discussed utilizing the experimental and theoretical approaches.