Self-assembled complexes between cage com-pounds 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 encap-sulated yet; the cavity of the cucurbit[7]uril can accommo-date a hexamethylenetetramine molecule to form a self- assembled host-guest inclusion. Moreover, both the cavity interaction of the cucurbit[7]uril with hexamethylenetetra-mine稨Cl and the portal interaction of the dipole carbonyl of the cucurbit[7]uril with hexamethylenetetramine稨Cl lead to form self-assembled capsules in which the hexamethylene-tetramine稨Cl are encapsulated in the hexamethylenetetra-mine稨Cl 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.
SHEN Yongqiang, XUE Saifeng, ZHAO Yunjie, ZHU Qianjiang & TAO Zhu Institute of Applied Chemistry, Guizhou University, Guiyang 550025, China Correspondence should be addressed to Xue Saifeng (e-mail: gzutao@ 263.net)
The experimental results reveal that solubility of cucurbiturils is related with acidity of solution and metal ions. In hydrochloric acid, cucurbituril is the most soluble one, and cucurbituril is the least soluble one. There is no significant influence of alkaline metal ion on the solubility of cucurbiturils. The solubility of cucurbituril increases greatly in a SrCl2 solution. However, increase of weight of cucurbiturils suggest that cucurbiturils can catch Ba2+in a solution.
