Structural investigation of bromide complexation with bipodal, tripodal and tetrapodal cationic molecules

Abstract

Nine multipodal cationic molecules with adaptable cyclic and acyclic amine functional groups along with bromide as the counterion have been synthesised and structurally characterised by single crystal X-ray diffraction. In the solid-state, the dicationic bipodal molecule has a pincer-like geometry while the tricationic tripodal molecule has a cavity-like geometry. The tetracationic tetrapodal molecule crystallised as the chair conformer as a result of steric crowding by the heterocyclic amine functional groups (imidazolium and pyrrolidinium), which prohibits arrangement of the heterocyclic amine substituents in the same direction. This study also illustrates that the different packing motifs (including linear and corrugated layers, and channels) are affected by the substituents at the central core for each type of multipodal molecule. CrystalExplorer was used to visualise these weak intermolecular interactions and to quantitatively summarise the interactions that contribute to the overall stability to the crystal structure.