Dual binding mode of alkylammonium cations to (1,3)-calix[5]crown-6 triesters

Abstract

Abstract Potentially heteroditopic receptors 1c-h are easily obtained by exhaustive alkylation of (1,3)-calix[5]crown-6 triols 1a ( R ′ = t Bu ) or 1b (R′ = H) with alkyl bromoacetates. 1H NMR titration experiments provide clear evidence for a dual (endo-cavity and/or exo-cavity) binding mode of alkylammonium cations to hosts 1c-h, depending on the shape of the guest and the size of substituents at the upper rim.