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

Self-assembled complexes between cage compounds cucurbitn = 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 cucurbit7]uril can accommodate a hexamethylenetetramine molecule to form a selfassembled host-guest inclusion. Moreover, both the cavity interaction of the cucurbit7]uril with hexamethylenetetramine·HCl and the portal interaction of the dipole carbonyl of the cucurbit7]uril with hexamethylenetetramine·HCl lead to form self-assembled capsules in which the hexamethylenetetramine·HCl are encapsulated in the hexamethylenetetramine·HCl “lidded” cucurbit7]uril. Although the structures of the portal and cavity to cucurbit5]uril are similar, there is no obvious interaction between decamethylcucurbit5]uril and hexamethylenetetramine, and also between cucurbit 6]uril or cucurbit8]uril and hexamethylenetetramine.