Biphenyl macrolactams in anion complexation. Selective naked-eye fluoride recognition

Two colorimetric anion sensors and allow for the selective differentiation of fluoride in the presence of other anions. Two different types of species have been observed in the complexation process, one of them is a co-ordination complex and the other is a salt generated by ligand deprotonation. The deprotonation reaction induces a conformational change, giving rise to a symmetrical species. This species is responsible for colour development. Ligand has a similar structure and does not give rise to any colour modification due to presence of the dimethylamino groups in the biphenyl moiety. The X-ray structure of ligand is also reported and compared with that of ligand , that had been previously described.