Interactions of Pyridine-Based Organic Cations as Structure-Determining Factors in Perovskite-Related Compounds AxPb(II)yBrz

We have synthesised and characterised 21 new ternary Pb(II) bromides with 16 different pyridine-based organic cations by single crystal XRD measurements. The dominating composition is APbBr₃ with 10 representatives, but also 6 examples for APb₂Br₅ were found. The systematic variation of topological aspects of the organic cations allowed conclusions on the influence of N−H⋅⋅⋅Br hydrogen bridges on the connectivity and bonding situation of the Pb−Br polyhedra. Additionally, it turned out, that further weak ionic interactions can have an influence, if the formation of N−H⋅⋅⋅Br hydrogen bridges is hindered by steric effects. In general, the high versatility of the dominating PbBr₆ octahedra, and in some cases higher or lower coordination numbers, allows conclusions on the parameters that influence pattern and extent of the N−H⋅⋅⋅Br bridges as the strongest structure-determining factor. Type and extent of N−H⋅⋅⋅Br bridges have also an impact on the distortion of the PbBr₆ octahedra ranging from nearly regular PbBr₆ octahedra to 2+2+2 and 1+2+2+1 patterns with significant lone pair activity. Finally, the connectivity mode of the octahedra relates to formation and strength of hydrogen bonds.