Proton transfer in host-guest complexation between a difunctional pillar[5]arene and alkyldiamines.

Host-guest complexation between a novel difunctional pillar[5]arene-based host H and alkyldiamines was fully investigated in both solution and the solid state. Proton transfer from the carboxylic acid groups to the amine units occurred in the principle by undergoing an acid-base reaction. Driven by the cooperativity of electrostatic interactions, multiple C-H···π interactions, and H-bonds, the guests penetrated into the cavity of H to form pseudorotaxane-type inclusion complexes with relatively high binding affinities.