Inclusion complex of riboflavin with cucurbit[7]uril: study in solution and solid state

Abstract

The aqueous solution of riboflavin and cucurbit[7]uril complex has been studied based on fluorescence and 1H NMR spectroscopic results. Upon addition of cucurbit[7]uril, the fluorescence intensity of riboflavin was quenched and a slight red shift was observed for the maximum emission peak. These results indicated that the cucurbit[7]uril–riboflavin complex was formed at a 1:1 mole ratio. The temperature-dependent inclusion constants were calculated, from which ΔH and ΔS values were calculated. Meanwhile, rationale of the interaction mechanism was also discussed based on 1H NMR results. The solid inclusion complex was prepared from co-evaporation method and characterised by differential thermal analysis and fluorescence lifetime analysis methods. The experimental results indicated that riboflavin and cucurbit[7]uril formed stable host–guest inclusion complex in both solution and solid states.