Solid-State Supramolecular Assemblies of Tryptophan and Tryptamine with Cucurbit[6]Uril

The crystal structure of the supramolecular exclusion
complexes
of cucurbit[6]­uril with amino acid d-tryptophan and its decarboxylation
product tryptamine have been determined. The supramolecular self-assembly
of the cucurbit[6]­uril with aromatic guests is guided by the combination
of ion-dipole, hydrogen bonding, and stacking interactions between
indole rings and glycouril groups of cucurbit[6]­uril and leads to
the formation of helical nanotubules in the case of tryptophan and
stacked columns in the case of tryptamine. The formation of the solid-state
complexes is dependent on the type of salt used for solubilization
of cucurbit[6]­uril which is explained in terms of the specific coordination
mode of cucurbit[6]­uril with magnesium ion.