Metal-free enantiomorphic perovskite [dabcoH2]2+[H3O]+Br−3 and its one-dimensional polar polymorph

Armand Budzianowski, Vaclav Petřiček and Andrzej Katrusiak

Volume 9(5) (September 2022)
IUCrJ (2022). 9 []
Authorised by IUCr electronic reprint of the article (open access)


The structure and stoichiometry of a new metal-free and ammonium-free compound [dabcoH2]2+H3O+Br3 (where [dabcoH2]2+ = 1,4-di­aza­bicyclo­[2.2.2]octane dication) correspond to the general formula ABX3 characteristic of perovskites. In enantiomorphic trigonal polymorph α of [dabcoH2]2+H3O+Br3, the corner-sharing [H3O]Br6 octahedra combine into a 3D framework embedding [dabcoH2]2+ dications in pseudo-cubic cages. In the more dense polymorph β, the face-sharing [H3O]Br6 octahedra form 1D polyanionic columns separated by [dabcoH2]2+ dications. These different topologies correlate with

different crystal fields around the cations and their different disorder types: orientational disorders of [dabcoH2]2+ dications and H3O+ cations in polymorph α and positional disorder of [H3O]+ cations in polymorph β. The orientational disorder increases the lengths of OH⋯Br hydrogen bonds in polymorph α, but NH⋯Br distances of ordered dabcoH2 dications are longer in polymorph β. The presence of polar [H3O]+ cations in [dabcoH2]2+H3O+Br3 polymorphs offers additional polarizability of the centres compared with analogous metal-free [dabcoH2]2+[NH4]+Br3 perovskite.






Selected images from the Supporting information. See there for full description.