Spectral study on the inclusion complex of cryptophane-E and CHCl3

Cryptophane-E was synthesized from vanillin by a three-step method, and its absorption and fluorescence spectroscopic properties were determined. Two absorption bands at about 245–260 and 280–290 nm were observed for cryptophane-E and the fluorescence emission maxima were at 320–330 nm depending on the solvent used. The interaction of cryptophane-E with CHCl3 was studied in detail by absorption and fluorescence spectroscopies. The results showed that cryptophane-E and CHCl3 can easily form a stable 1:1 host–guest inclusion complex. Their binding constant (K) was determined by Benesi–Hildebrand equation and the nonlinear least squares fit method. The binding constant is largest in ethyl acetate, followed by dioxane and with acetonitrile as the smallest. In addition, the effect of guest volume on the host–guest inclusion complex was investigated. Guest molecules including CH2Cl2 and CCl4 were unable to form inclusion complex with cryptophane-E because of sizes mismatching with the host cavity.