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

Abstract

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.

Cyclodextrin Dimers as Receptor Molecules for Steroid Sensors

“…[10] In a previous paper, we reported on the use of fluorophore-appended cyclodextrin-calix [4]arene couples as sensing molecules with an enlarged cavity. [11] Their sensing behavior, however, depended heavily on the aggregation state of the hosts and the host ± guest complexes. [12] Ueno and co-workers have used biomolecules as large caps for cyclodextrin-based sensing molecules.…”

“…The maximum emission wavelength for an aqueous solution of 9 is at 540 nm. The blue-shift relative to N,N-dimethyl dansylamide, which was reported to have an emission maximum at 572 nm, [11] indicates that the dansyl Table 2. Thermodynamic parameters (298 K) for the interaction between dimer 6 and bile salts.…”

Sensor Development Using Existing Scaffolds

“…The selectivity of the conjugate toward alkyl amines is due to the cooperative binding of both the crown ether and CD moieties [30]. Reinhoudt and coworkers prepared CD-calix [4]arene conjugates [31]. The fluorophore was attached to the upper rim of the calix [4]arene moiety.…”

Cetyltrimethylammonium assay using fluorescence probe berberine and a competitive host–guest complexation with butylated β-cyclodextrin

“…CDs are basically spectroscopically inert. To transduce the complexation of CDs with guests into a physical signal, some modified CDs bearing a fluorescence probe have been synthesized and their complexation behaviors acting as molecular sensors have been investigated [18][19][20]. Sensing is based on the competition for the hydrophobic cavity between a guest molecule and the covalently linked fluorophore resulting in a change in optical properties.…”