Host–guest complexes of cucurbituril with the 4-methylbenzylammonium lon, alkali-metal cations and NH₄⁺

Abstract

Kinetic measurements indicate the existence of two different complexes of cucurbituril with 4-methylbenzylammonium ions: (i) an association complex, where the ammonium group binds to one of the polar portals of cucurbituril and the hydrophobic part extends into the solvent, and (ii) an inclusion complex, where the hydrophobic part extends into the cavity of cucurbituril. This complex is used as an indicator for the binding of simple monovalent cations to cucurbituril. Stability constants are reported for the 1 : 1 complexes of cucurbituril with different cations.