Date Published: June 01, 2018
Publisher: International Union of Crystallography
Author(s): Xiao-Gang Chen, Ji-Xing Gao, Xiu-Ni Hua, Wei-Qiang Liao.
Two new organic–inorganic hybrid sodium halides based on the piperazinediium dication have been synthesized, with C4H12N2·NaI3 presenting a three-dimensional perovskite structure and 3C4H12N2·NaI4·3I·H2O showing a three-dimensional hydrogen-bonded supramolecular network.
In recent decades, three-dimensional organic–inorganic hybrid perovskites have been of interest to researchers, not only for their remarkable structural variability and highly tunable properties, but also for their rich physical properties, such as superconductivity, ionic conductivity and ferroelectric related properties (Jin et al., 2009 ▸; Saparov & Mitzi, 2016 ▸; Veldhuis et al., 2016 ▸). Such hybrid perovskites have a simple generic formula of AMX3 (A = organic cation, M = metal cation and X = halogen anion) and the structural characteristic of corner-sharing MX6 octahedra. Among them, there have been a large number of reports on the halometallates of PbII and SnII ions because of their superior semiconducting properties, but related systems containing alkali metal halides are rare (Lee et al., 2003 ▸; Shi et al., 2017 ▸; Liao et al., 2016b ▸; Galkowski et al., 2016 ▸; Yang et al., 2015 ▸; Liao et al., 2016a ▸). To be precise, the first alkali metal halide perovskites, RMCl3 (R = piperazine and M = K, Rb and Cs), were found less than ten years ago (Paton & Harrison, 2010 ▸). In recent years, due to the development of molecular ferroelectric materials (You et al., 2017 ▸; Xu et al., 2017 ▸; Liao et al., 2017 ▸), three-dimensional alkali metal halide perovskites have attracted the attention of researchers again. Just last year, Xiong and co-workers reported two high-Tc three-dimensional perovskite ferroelectric materials, i.e. [3-ammoniopyrrolidinium]·RbBr3 and [N-methyl-1,4-diazoniabicyclo[2.2.2]octane]·RbI3 (Pan et al., 2017 ▸; Zhang et al., 2017 ▸).
Two new organic–inorganic hybrid sodium halides have been synthesized by adjusting the stoichiometric ratio of sodium iodide and piperazine. C4H12N2·NaI3, 1, presents an interesting three-dimensional perovskite structure. However, compound 3C4H12N2·NaI4·3I·H2O, 2, features a singular three-dimensional hydrogen-bonded network. The different structures of compounds 1 and 2 show that the stoichiometric ratio plays a key role in the synthesis of various frameworks.