[Interaction of cucurbit[ n ]urils and quinoline or its derivatives].

The structures and fluorescence characteristics of cucurbit[n = 6-8]urils with quinoline, isoquinoline and 7-methyl quinoline have been investigated by fluorescence spectrophotometry. Compared to NMR techniques, thefluorometric analysis methodrevealed that there are not only obvious interactions of quinoline or its derivates and cucurbit[7]uril, but also interactions of quinoline or its derivates and cucurbit[6]uril or cucurbit[8]uril which can not be observed by using 1H NMR technique. The experimental results also revealed that quinoline, isoquinoline and 7-methyl quinoline were included by cucurbit[6-8]uril with different ratios. There could be three kinds of interactions of cucurbit[n]urils and the guests: (a) cavity interaction, including hydrophobic forces and Van der Waals contact forces between macrocycles and cages; (b) portals ion-dipole interaction, or electrostatic interaction of the positive charge of the guests and the carbonyl groups at the portals of cucurbit[n]uril; (c) size interaction which requires the size of the guest matching a cucurbit[n]uril.