Ion pair recognition of ditopic receptor bearing silanol groups as anion recognition sites and a 2,2′-bipyridine moiety as a metal-coordination site

A ditopic receptor 1 bearing silanol groups as anion recognition sites and a 2,2′-bipyridine moiety as a metal-coordination site was synthesized. The X-ray crystallographic analysis revealed that the receptor 1 simultaneously associated Ag+ at the bipyridine site and NO 3 - at the anion recognition site surrounded by two silanol groups and one C–H proton of the bipyridine. The titration experiments suggested the large affinity of the receptor with AgNO3, caused by the cooperative cation and anion binding. The cooperative effect of metal cation could enhance anion recognition property of silanol-based receptor.