Abstract
A γ-cyclodextrin (γ-CyD) derivative (1) having a pyrene moiety, connected through a 4, 13-diaza-18-crown-6 ether moiety to γ-CyD, was synthesized and evaluated for guest binding and sensing properties. In aqueous solution, 1 existed as an association dimer in which the secondary hydroxyl sides faced each other to accommodate two pyrene moieties. Photo-induced electron transfer (PET) between the amino group and the excited pyrene moiety regulated the monomer fluorescence intensity of 1. The monomer-dimer equilibrium and the PET indicated that 1 may be used as a host capable of detecting guest complexation by changes in fluorescence intensity from the pyrene moiety. Deoxycholic acids were found to be good guests for detection by 1, and deoxycholic acid itself induced different fluorescence changes compared to the other deoxycholic acids. This indicated that 1 could recognize the position of the hydroxy groups on the steroidal framework. The azacrown part may participate in the guest selectivity for the deoxycholic acids by regulating the distance between the amino group and the pyrene moiety, modifying PET efficiency.
