Colorimetric signaling of Hg2+ ions by a nitrobenzoxadiazole-appended cyclen-triester

A novel Hg2+-selective colorimetric sensor based on a cyclen–nitrobenzoxadiazole (NBD) conjugate was investigated. A cyclen derivative with three ester ligands was used as the binding site and the NBD moiety acted as the reporting chromogenic subunit. Interaction of 1 with Hg2+ ions resulted in a pronounced color change from pink to yellow, and fluorescence signaling was also possible. Selective colorimetric signaling of Hg2+ ions by NBD-functionalized cyclen with a detection limit of 1.5 × 10−6 M in aqueous environments was successfully achieved.