Host–guest complexes between cucurbit[n]urils and acetanilides having aminopropyl units

2-(Propylamino)acetamide of aniline (1a), and bis-2-(propylamino)acetamide of ortho- (1b) and para-(1c) phenylenediamine form host–guest complexes with CB[6], CB[7] and CB[8] as evidenced by the variations in the 1H NMR spectroscopy chemical shifts and observation in MALDI-TOF-MS and ESI-MS of ions at the corresponding mass. Binding constants for the 1:1 complexes were estimated from fluorescence titrations and were in the range 105–106 M−1. Models based on molecular mechanics for these supramolecular complexes are provided. In spite of the different geometries arising from the ortho- or para-substitution, phenylenediamides form complexes of similar strength in which the hydrophobic alkyl chains are accommodated inside the host cavity. Formation of these host–guest complexes in the solid state was also achieved by modifying an aminopropyl silica with chloroacetanilides and preparing three silica having analogues of compounds 1a–c anchored to the solid particles. Titrations showed, however, that these solids can adsorb a large percentage of CBs by unselective interactions that are not related to the formation of inclusion complexes.

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► Acetalinides with lateral amino groups form complexes with cucurbit[n]urils.
► An aminopropyl silica has been modified attaching acetanilides pending moieties.
► Cucurbiturils adsorb onto modified silica in a specific and unspecific way.