A high phase transition temperature organic–inorganic Sn(iv)-based metal halide designed by applying amino positional isomerism to the cation†

Abstract

Organic–inorganic metal halides (OIMHs) have recently received extensive interest from researchers because of their diverse functionalities, such as phase transition. A high phase transition temperature (T_c) is highly desirable for the practical applications of OIMH phase transition materials. Here, by applying cation amino positional isomerism to the lead-free Sn(IV)-based OIMH [n-butylammonium]₂SnCl₆ ([NBA]₂SnCl₆), which has a relatively low T_c of 226 K, [sec-butylammonium]₂SnCl₆ ([SBA]₂SnCl₆) was successfully designed with T_c as high as 430 K. This high T_c of [SBA]₂SnCl₆ is higher than that of most lead-free OIMHs, and is outstanding among OIMHs. [NBA]₂SnCl₆ and [SBA]₂SnCl₆ are isostructural at room temperature, but the differences in their chemical composition, crystal structure, and phase-transition mechanisms contribute to their distinct T_c. In addition, [NBA]₂SnCl₆ and [SBA]₂SnCl₆ have wide band gaps (E_g) of about 3.92 eV and 3.95 eV, respectively. This work provides a new strategy for designing high-T_c OIMH materials.