Encapsulation of fluoride and hydrogen sulfate dimer by polyammonium-functionalised first- and second-generation tripodal: cavity-induced anion encapsulation

Abstract

AbstractDesign, synthesis and complexation with inorganic anions of first (1L) and second (2L) generation tripodal polyamine receptors are reported here. The C3v symmetric second-generation tripodal receptor (2L) possesses large enough cavity to encapsulate larger hydrogen sulfate dimer in a unimolecular capsular fashion [(HSO4)2⊂2]. The dimer is stabilised by (NH)+⋯O type H-bonding and electrostatic interactions between and ammonium group. Water of crystallisation form hybrid anion–water cluster [(HSO4)–(H2O) with ions located outside the cavity. The [(HSO4)–(H2O) cluster and Cl⋯Cl halogen bond play templating role in the supramolecular aggregation of unimolecular capsule [(HSO4)2⊂2]. On the other hand, first-generation receptor (1L) encapsulates only fluoride ion due to its smaller cavity size and thus form unimolecular fluoride complex [F⊂1]. Overall study shows cavity size-induced anion encapsulation. All complexes are well characterised by FT-IR, NMR, TGA, DSC and XRD experiments.