A fluorescent chemosensor based on optically active 2,2'-binaphtho-20-crown-6 for metal ions

Abstract

A chiral conjugated polymer can be obtained by the polymerization of (S)-6,6′-dibromo-2,2′-binaphtho-20-crown-6 and 1,4-divinyl-2,5-dibutoxybenzene via a palladium-catalyzed Heck cross-coupling reaction. The chiral conjugated polymer shows strong green-blue fluorescence. The responsive properties of the chiral polymer to metal ions were investigated using fluorescence and UV-visible absorption spectra. K+,Pb2+,Cd2+ and Ba2+ enhance the fluorescence of the polymer; in contrast, Hg2+ causes effective quenching of the fluorescence of the polymer. The obvious influences on the fluorescence indicate that the 2,2′-binaphtho-20-crown-6 moiety plays an important role in fluorescence recognition for Hg2+ due to the effective photo-induced electron transfer or charge transfer between the conjugated polymer backbone and the receptor ions. The responsive properties of the polymer to metal ions show that the chiral conjugated polymer incorporating 2,2′-binaphtho-20-crown-6 moieties in the main-chain backbone as recognition sites can act as an excellent fluorescent probe for the sensitive detection of Hg2+. © 2010 Society of Chemical Industry.