Highly Selective Fluorescent Sensors for Hg2+ and Ag+ Based on Bis-triazole-Coupled Polyoxyethylenes in MeOH Solution

Fluorescent chemosensors 6-9, with variable length polyoxyethylenes between two triazolylmethyl ether units, have been synthesized under "click" conditions in which the bis-triazoles and polyoxyethylenes were used as metal-ion binding sites and the pyrenes as fluorophores. Of the 15 metal ions screened, the fluorescence of chemosensors 6-9 in methanol solution was found to be selectively quenched by only Hg2+ and Ag+. In contrast, the fluorescence of control compound 10, a [(triazol-4-yl)methoxymethyl]pyrene, was quenched by only Hg2+. These results imply that the recognition of Hg2+ does not need the cooperation of two triazole groups. Binding constants for the interactions of 6-9 with Ag+ increased as the chain length of the polyoxyethylene increased. Finally, a very high selectivity of compound 9 towards Hg2+ in aqueous methanol solution was observed. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)