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.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)