Fluorescent amino-β-cyclodextrin derivative as a receptor for various types of alcohols having cyclic and macrocyclic rings

Abstract

The cyclic- and macrocyclic-alcohol sensing in aqueous solution by an amino-β-cyclodextrin (amino-β-CDx), 1, bearing a naphthalene fluorophore has been investigated by fluorescent and induced circular dichroism (ICD) spectrophotometry. The host-guest 1:1 stoichiometric binding was confirmed mainly by fluorescent titration method. The binding constants ( K f) of the 1:1 host-guest inclusion complexes were found to be in the range of 10 2–10 5 mol −1 dm 3, depending on the shape and size of hydrophobic moiety of alcohol molecules. This indicates that the β-CDx cavity takes part in the guest sensing and the partially self-included naphthalene probe of 1 would extrude from the cavity upon binding with guest molecules. Addition of guests to the host 1 solution causes appreciable changes both in fluorescent and ICD intensity. The geometry of the inclusion complexes and the inclusion process were simulated by molecular mechanics using MM2 force field. The optimized steric-energy differences of the various inclusion complexes indicate that the nonbonded van der Waals (non-1,4-VDW) interaction between host and guest play a significant role in the induced-fit inclusion process.