Alkyl modification to optimize the ferroelastic properties of molecular crystals

Abstract

Ferroelastics, an important type of ferroic material, have significant value in applications such as shape memory, mechanical switches, intelligent sensors, etc. With the aim of developing new technologies, ferroelastics with only single properties have certain limitations that hinder expansion of their applications. Thus, it is still a challenge to find multifunctional ferroelastic materials, especially those with multi-dielectric responses and fluorescence properties. Here, under the guidance of a strategy of alkyl modification, (EMP)PbBr₃ (EMP = N-ethyl-N-methyl-3-pyrroline) (compound 2) was successfully obtained by modifying the parent compound (DMP)PbBr₃ (DMP = N,N-dimethyl-3-pyrroline) (compound 1). Of note, compound 2 was improved to have a triple dielectric response compared with the double dielectric response of compound 1, and both the ferroelastic phase transition temperature and photoluminescence quantum yield of compound 2 were improved. Such changes make compound 2 potentially applicable in smart electronic devices. This work provides some insights into the search for multifunctional ferroelastic materials.