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

摘要

Design, synthesis and complexation with inorganic anions of first (L-1) and second (L-2) generation tripodal polyamine receptors are reported here. The C-3v symmetric second-generation tripodal receptor (L-2) possesses large enough cavity to encapsulate larger hydrogen sulfate dimer in a unimolecular capsular fashion [(HSO4)(2)subset of 2]. The dimer is stabilised by (NH)O+ type H-bonding and electrostatic interactions between HSO4- and ammonium group. Water of crystallisation form hybrid anion-water cluster [(HSO4)-(H2O) HSO4- ions located outside the cavity. The [(HSO4)-(H2O) HSO4- cluster and ClCl halogen bond play templating role in the supramolecular aggregation of unimolecular capsule [(HSO4)(2) subset of(2)]. On the other hand, first-generation receptor (L-1) encapsulates only fluoride ion due to its smaller cavity size and thus form unimolecular fluoride complex [F subset of 1]. Overall study shows cavity size-induced anion encapsulation. All complexes are well characterised by FT-IR, NMR, TGA, DSC and XRD experiments.