Synthesis of BINOL–xylose-conjugates as “Turn-off” fluorescent receptors for Fe3+ and secondary recognition of cysteine by their complexes

Abstract

A novel chiral fluorescence “turn-off” sensor was synthesised using the click reaction. The sensor was a BINOL–xylose derivative, modified at the 2-position and linked by 1,2,3-triazole. It was structurally characterized by ¹HNMR, ¹³CNMR, ESI-MS and IR analysis. The selectivity of R-β-D-2 in methanol solution has been studied. Among the 19 transition metal ions, alkaline metal ions and alkaline earth metal ions studied, R-β-D-2 had a selective fluorescence quenching reaction for Fe³⁺. The detection limit of R-β-D-2 for Fe³⁺ was 0.91 μmol L⁻¹. Complexation between R-β-D-2 and Fe³⁺ was investigated by ESI-MS and ¹HNMR. The stoichiometric ratio of R-β-D-2 was 1 : 1. In addition, the R-β-D-2–Fe³⁺ complex was titrated with 20 naturally occurring amino acids and Hcy with GSH. It was found that the complex R-β-D-2–Fe³⁺ had a secondary recognition effect on Cys by switching to fluorescence.