Pyrenyl-imino-C2-glucosyl conjugate: synthesis, characterization, and ratiometric and reversible OFF-ON receptor for Hg(2+).

A pyrenyl-imino-C2-glucosyl conjugate, L, has been synthesized and characterized. The L exhibits selective chromogenic as well as fluorescent property towards Hg(2+) in a ratiometric manner by showing ∼30 fold enhanced fluorescence emission intensity. The fluorescence enhancement continues to be there even in the presence of thirteen other competitive metal ions studied. The sensing of Hg(2+) is well demonstrated using various techniques, such as, fluorescence, absorption, visual color under UV light and ESI MS. A minimum detection limit of 18±2ppb was shown by L for Hg(2+) in ethanol. All the experimental studies carried out supported the formation of 2:1 complex between L and Hg(2+). The structure of the 2:1 complex was modeled at ab initio using HF and found a structure where Hg(2+) is sandwiched between the two pyrenyl moieties. The reversibility and reusability of L has been demonstrated using fluoride ion.