Rhodamine—pyrene conjugated chemosensors for ratiometric detection of Hg~(2+) ions: Different sensing behavior between a spirolactone and a spirothiolactone

摘要

Two novel rhodamine—pyrene conjugated chemosensors were successfully designed and synthesized, which exhibited high affinity to Hg~(2+) ions. As ratiometric chemosensors, each displayed highly selective and sensitive colorimetric and fluorogenic dual-responses toward Hg~(2+). The comparison of two chemosensors indicated that the spirothiolactone containing sensor was superior to the spirolactone analog in sensing behavior when detecting Hg~(2+), presumably due to the thiophilic nature of mercury and the different sensing mechanisms in operation. Upon interaction with Hg~(2+), the spirothiolactone showed a 1:1 stoichiometry for the Hg~(2+) complex, accompanied with a weakened fluorescence resonance energy transfer (FRET) behavior. However, the spirolactone was hydrolyzed and consequently induced the monomer-excimer switch of the resulted pyrene in the presence of Hg~(2+) ions.