A "clicked" macrocyclic probe incorporating Binol as the signalling unit for the chiroptical sensing of anions

We describe a macrocyclic chiroptical sensor for the detection of halide anions, with the Binol moiety acting as the CD signalling unit. The macrocycle is conveniently synthesized using CuAAC “click” reactions in the cyclization step; this methodology installs 1,2,3-triazole moieties within the macrocyclic backbone, able to directionally bind anions by means of CH…X- hydrogen bonds. 1H NMR complexation studies in CDCl3 reveal weak binding to halide and aliphatic carboxylate anions. Halide anions, however, when held into the macrocyclic cavity, are able to trigger a large chiroptical response originating from the steric interaction with the Binol moiety, which changes its dihedral angle, thus modulating its characteristic CD signature.