Crystal structures and phase transitions in two new hybrid crystals: (Me 3 NCH 2 CH 2 X) 4 [Ni(NCS) 6 ] (X = Cl and Br)

Understanding phase transitions in multi-component crystals is of importance for regulating specified functional materials. Herein, we present two new organic-inorganic hybrid crystals, (Me 3 NCH 2 CH 2 X) 4 [Ni(NCS) 6 ] (X = Cl and Br), revealing distinct phase transitions. Specifically, the Clsubstituted cations weakly interact with discrete inorganic part hence reveal step-wise dynamic changes upon heating, which result in multi-step solid-solid phase transitions ( P 1 over bar -P 2 1 / n -A 2/ a -Cmce ) including a ferroelastic one with a spontaneous strain of 0.0475. Whereas the Br-substituted cations with larger steric effect prevent the solid-solid phase transition but give a solid-liquid phase transition at above 419 K. The present instances well demonstrate the complicity for multi-component crystals arising from the delicate balance established by abundant weak intermolecular interactions, and inspire the design of novel phase-transition materials by judiciously assembling multi-component crystals. (c) 2023 Published by Elsevier B.V. on behalf of Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences.