Hierarchical study of mono- and multicharged imidazolium encapsulation in p-sulfonatocalix[4]arene molecular capsules

Four ternary multi-component crystal structures comprising water-soluble p-sulfonatocalix[4]arene anion as the cavitand in the presence of different types of positively charged guest molecules comprising 1-butylimidazolium, 3,3 '-(1,4-phenylenebis(methylene))bis(1-methylimidazolium), 3,3 ',3 ''-(benzene-1,3,5-triyltris(methylene))tris(1-methylimidazolium), or 3,3 ',3 '',3 '''-(benzene-1,2,4,5-tetrayltetrakis(methylene))tetrakis(1-methylimidazolium) and aquated lanthanide(iii) ions (Gd(iii) or Ce(iii)) are reported. Careful crystallographic analysis shows that all positively charged imidazole rings are encapsulated by p-sulfonatocalix[4]arene for 1-butylimidazolium and 3,3 '-(1,4-phenylenebis(methylene))bis(1-methylimidazolium), however, partial encapsulation was observed for 3,3 ',3 ''-(benzene-1,3,5-triyltris(methylene))tris(1-methylimidazolium) and 3,3 ',3 '',3 '''-(benzene-1,2,4,5-tetrayltetrakis(methylene))tetrakis(1-methylimidazolium). The formation of a molecular capsule prevails in all structures regardless of the type of guest species. Supermolecules in three of the complexes self-assemble into a bilayer arrangement in the extended structure, whilst those involving p-sulfonatocalix[4]arene and 1-butylimidazolium form hydrated channels through alternative packing.

Automated summary

This study reports four ternary multi-component crystal structures containing water-soluble p-sulfonatocalix[4]arene anion as the cavitand, along with different types of positively charged guest molecules and aquated lanthanide(iii) ions (Gd(iii) or Ce(iii)). Crystallographic analysis reveals that all positively charged imidazole rings are encapsulated by p-sulfonatocalix[4]arene. A molecular capsule is formed in all structures, regardless of the type of guest species.