NMR study on self-assembled cage complex of hexamethylenetetramine and cucurbit[n]urils

Self-assembled complexes between cage compounds cucurbit[n = 5–8]urils and hexamethylenetetramine were studied by using NMR techniques. Experimental results reveal that hexamethylenetetramine can lid cucurbit [5] uril to forming self-assembled capsules in which nothing is encapsulated yet; the cavity of the cucurbit[7]uril can accommodate a hexamethylenetetramine molecule to form a selfassembled host-guest inclusion. Moreover, both the cavity interaction of the cucurbit[7]uril with hexamethylenetetramine·HCl and the portal interaction of the dipole carbonyl of the cucurbit[7]uril with hexamethylenetetramine·HCl lead to form self-assembled capsules in which the hexamethylenetetramine·HCl are encapsulated in the hexamethylenetetramine·HCl “lidded” cucurbit[7]uril. Although the structures of the portal and cavity to cucurbit[5]uril are similar, there is no obvious interaction between decamethylcucurbit[5]uril and hexamethylenetetramine, and also between cucurbit [6]uril or cucurbit[8]uril and hexamethylenetetramine.