A Lead-Free Ferroelectric 2D Dion-Jacobson Tin Iodide Perovskite.

2D hybrid organic-inorganic halide perovskites emerge as a new class of 2D semiconductors with the potential to combine excellent optoelectronic properties with symmetry-enabled properties such as ferroelectricity. Although many lead-based ferroelectric 2D halide perovskites are reported, there is yet to be a conclusive report of ferroelectricity in tin-based 2D perovskites. Here, the structures and properties of a new series of 2D Dion-Jacobson (DJ) Sn perovskites: (4AMP)SnI, (4AMP)(MA)SnI, and (4AMP)(FA)SnI (4AMP = 4-(aminomethyl)piperidinium, MA = methylammonium, and FA = formamidinium), are reported.

Crystallographic and spectroscopic characterization of 3-chloro-5-fluoro-salicyl-aldehyde.

The title compound (systematic name: 3-chloro-5-fluoro-2-hy-droxy-benzaldehyde), CHClFO, is a dihalogenated salicyl-aldehyde derivative that has been studied for its anti-bacterial characteristics. The salicyl-aldehyde engages in intra-molecular hydrogen bonding with an O-H⋯O distance of 2.6231 (19) Å while the mol-ecules pack together weak inter-molecular C-H⋯O, C-H⋯F and F⋯O inter-actions and offset face-to-face π-stacking.