Dual emission of a bis(pyrene)-functionalized, perbenzylated beta-cyclodextrin

A bis(pyrene)-functionalized β-cyclodextrin (1) has been prepared in two steps from perbenzylated β-cyclodextrin. This compound shows dual emission properties, which arise from the pyrenyl chromophores. Upon excitation of 1 at 355 nm, monomer blue fluorescence (386, 407 and 428 nm) is observed in DMSO solution, whereas excimer green fluorescence (477 nm) is seen upon addition of ≥20 vol% water in DMSO. This suggests that modified β-cyclodextrin 1 changes its shape in response to the environment. The sensing properties of 1 towards carboxylic acids and alcohols were investigated in H2O–DMSO (80 : 20 v/v). Monomer fluorescence is restored selectively by medium length normal carboxylic acids, …