Syntheses and crystal structures of a new family of hybrid perovskites: C5H14N2· A Br3·0.5H2O (A = K, Rb, Cs)

Abstract

The syntheses and crystal structures of three hybrid perovskites, viz. poly[1-methyl-piperizine-1,4-diium [tri-μ-bromido-potassium] hemihydrate], {(C₅H₁₄N₂)[KBr₃]·0.5H₂O} _n , (I), poly[1-methyl-piperizine-1,4-diium [tri-μ-bromido-rubidium] hemihydrate], {(C₅H₁₄N₂)[RbBr₃]·0.5H₂O} _n , (II), and poly[1-methyl-piperizine-1,4-diium [tri-μ-bromido-caesium] hemihydrate], {(C₅H₁₄N₂)[CsBr₃]·0.5H₂O} _n , (III), are described. These isostructural (space group Amm2) phases contain a three-dimensional, corner-sharing network of distorted ABr₆ octa-hedra (A = K, Rb, Cs) with the same topology as the classical perovskite structure. The doubly protonated C₅H₁₄N₂ ²⁺ cations occupy inter-stices bounded by eight octa-hedra and the water mol-ecules lie in square sites bounded by four octa-hedra. N-H⋯Br, N-H⋯(Br,Br), N-H⋯O and O-H⋯Br hydrogen bonds consolidate the structures.

Keywords: crystal structure; hybrid perovskite; hydrogen bonding.

Figure 1

The asymmetric unit of (I) expanded to show the complete C₅H₁₄N₂ ²⁺ cation, the complete potassium coordination polyhedra and the water mol­ecule (50% displacement ellipsoids). Symmetry codes: (i) x, 1 − y, z; (ii) 2 − x,  − y,  + z; (iii) x, y − ,  + z; (iv) 2 − x, 1 − y, z; (v) 1 − x, 1 − y, z; (vi) 1 − x,  − y,  + z; (vii) x, y − ,  + z.

Figure 2

Polyhedral plot of the extended structure of (I) viewed down [011] with the K1Br₆ octa­hedra coloured lilac and K2Br₆ blue.

Figure 3

Comparison of the structures of (a) MEXMAG (redrawn from Chen et al., 2018 ▸), (b) (I) and (c) GUYMIX (redrawn from Paton and Harrison, 2010 ▸). In MEXMAG, (I) and GUYMIX, the two octa­hedral cages shown are stacked in the [001], [100] and [001] directions, respectively. Note the alternation of water mol­ecules and empty sites in (I) with respect to the [100] direction whereas GUYMIX has a water mol­ecule in every square site in the [001] direction.