Novel Water-Soluble β-Cyclodextrin−Calix[4]arene Couples as Fluorescent Sensor Molecules for the Detection of Neutral Analytes

The synthesis and the host−guest chemistry of two novel fluorescent β-cyclodextrin−calix[4]arene couples 1 and 2 is described. The compounds were prepared by coupling a β-cyclodextrin linked with an aminoxylyl spacer with two different calix[4]arene building blocks each bearing a fluorophore. The fluorophores attached to 1 and 2 are the 2-naphthylamine and the dansyl moiety, respectively. The unsymmetric calix[4]arene functionalization was achieved by monoprotection of the 1,3-diformylcalix[4]arene. The host molecules 1 and 2 were used as fluorescent probes for several organic analytes in aqueous solution. 1 shows sensitivity for a series of neutral organic guest species, such as steroids, terpenes, and other natural products. In contrast, compound 2 does not show sensitivity for organic analytes in aqueous solution. The different behavior of the two fluorescent probes 1 and 2 is explained by the different strength of self-inclusion of each fluorphoric group into the β-cyclodextrin cavity.