Pyrenyl-imino-C2-glucosyl conjugate: synthesis, characterization, and ratiometric and reversible OFF–ON receptor for Hg²⁺

Abstract

A pyrenyl-imino-C2-glucosyl conjugate, L, has been synthesized and characterized. The L exhibits selective chromogenic as well as fluorescent property towards Hg²⁺ 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 Hg²⁺ is well demonstrated using various techniques, such as, fluorescence, absorption, visual color under UV light and ESI MS. A minimum detection limit of 18 ± 2 ppb was shown by L for Hg²⁺ in ethanol. All the experimental studies carried out supported the formation of 2:1 complex between L and Hg²⁺. The structure of the 2:1 complex was modeled at ab initio using HF and found a structure where Hg²⁺ is sandwiched between the two pyrenyl moieties. The reversibility and reusability of L has been demonstrated using fluoride ion.