Spectroscopic study the interaction of cucurbit[n]urils with 1-naphthol, 2-naphthol

Interaction of cucurbit[n]urils with two naphthol isomers and the influence of pH on the interaction were studied by using UV-Vis spectroscopy and fluorescence spectrophotometry. The experimental results revealed that cucurbit[8]urils always forms a 1 : 1 complex with the naphthol isomers. However, UV-Vis spectroscopy and fluorescence spectrophotometry method showed no obvious interaction of cucurbit[6]urils and cucurbit[7]urils with naphthol isomers in all pH values. Formation constant of K-f was found to be 4.2 x 10(4) L . mol(-1), 1.6 x 10(4) L . mol(-1) of 1-naphthol and 2-naphthol with cucurbit[8]urils respectively by using fluorescence spectrophotometry. Formation constant of Kf was found to be 4.2 x 10(4) L . mol(-1), 5.4 x 10(4) L . mol(-1) of 1-naphthol and 2-naphthol with cucurbit[8]urils respectively by using UV-Vis spectroscopy. There is no interaction between cucurbit[8]urils and the naphthol isomers in strong alkalescent medium. The cucurbit[8]urils could include the guest with a 1 : 1 ratio in acid and neutral medium.