Investigation on photophysical properties of a substituted 3H-indole-modified β-cyclodextrin: I. Conformation in water and recognition mechanism as a chemosensor

A substituted 3H-indole-modified β-cyclodextrin (β-CD), mono-6-deoxy-(2-[(p-amino) phenyl]-3,3-dimethyl-5-carboxyl-3H-indole)-β-CD (compound A) has been synthesized and characterized by elemental analysis, mass spectrum (MS) and 1H NMR. Induced circular dichroism (ICD), time-resolved fluorescence and computational analysis yield information on the molecular structure that compound A adopts rim-covering conformation in aqueous solution. It forms the 1:1 (guest:host) inclusion complex by addition of native β-CD. Novel recognition behavior of compound A is investigated by means of ICD, time-resolved and steady-state fluorescence. In contrast to the behavior of most conventional CD-based chemosensors with self-inclusion conformation, the fluorescence intensity of this new kind chemosensor is increased upon addition of guest molecules. This new chemosensor exhibits high sensitivity to acyclic and adamantine molecules, but not to the bile acids.