Synthesis of BINOL–xylose-conjugates as “Turn-off” fluorescent receptors for Fe(3+) and secondary recognition of cysteine by their complexes

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 (1)HNMR, (13)CNMR, 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 Fe(3+). The detection limit of R-β-d-2 for Fe(3+) was 0.91 μmol L(−1). Complexation between R-β-d-2 and Fe(3+) was investigated by ESI-MS and (1)HNMR. The stoichiometric ratio of R-β-d-2 was 1 : 1. In addition, the R-β-d-2–Fe(3+) complex was titrated with 20 naturally occurring amino acids and Hcy with GSH. It was found that the complex R-β-d-2–Fe(3+) had a secondary recognition effect on Cys by switching to fluorescence.