The interaction between cucurbit[n]uril (n＝7 or 8) (Q[7], Q[8]) and diaminonaphthalene isomers, such as 1,8-diaminonaphthalene (g1), 2,3-diaminonaphthalene (g2), 1,5-diaminonaphthalene (g3) was studied by UV spectroscopy, fluorescence spectrophotometry and ¹H NMR technique. The experimental results revealed that the diaminonaphthalene isomers g2 and g3 as molecular guests were bound in the cavity of Q[7] in a ratio of 1∶1 while a portal interaction of the isomer g1 with Q[7] in a ratio of 1∶1 was observed. Interaction ratios of Q[8] with the three guest compounds were different: Q[8] bind g2 to form an inclusion complex in a ratio of 1∶2, and Q[8] bind g1 or g3 to form a less soluble host-guest product in a ratio of 1∶1. The results also showed that the stability of the inclusion complexes was related to the pH of solution: the inclusion complexes of Q[7] with g1, g2 or g3 were decomposed completely at pH＞6.0, and the inclusion complexes of Q[8] with g1, g2 or g3 were decomposed completely at pH＞12.0. Competitive experiments showed that the guests g1, g2 and g3 bound by Q[7] can be substituted by competitive guest 1-amineadmantane•HCl, and the guests g1 and g3 bound by Q[8] can be substituted by competitive guest 1,10-diaminodecane•2HCl completely, however, only part of g3 bound by Q[8] can be substituted by competitive guest 1,10-diaminodecane•2HCl.

Key words: UV absorption spectroscopy, fluorescence spectrophotometry, ¹H NMR technique, interaction of host-guest, pH influence