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 APbBr(3) with 10 representatives, but also 6 examples for APb(2)Br(5) were found. The systematic variation of topological aspects of the organic cations allowed conclusions on the influence of N-H center dot center dot center dot 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 center dot center dot center dot 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 center dot center dot center dot Br bridges as the strongest structure-determining factor. Type and extent of N-H center dot center dot center dot 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.