New ferrocene-pyrene dyads bearing amide/thiourea hybrid donors for anion recognition

Two new ferrocene-pyrene dyads (1 and 2) bearing amide and thiourea donors were designed and prepared for anion recognition. The structure of 1 was also characterized by X-ray single crystal analysis. The anion recognition ability of 1 and 2 was fully investigated by elecotrochemical and fluorescent techniques. In CH3CN solution, both 1 and 2 showed a good electrochemical sensing toward F-, AcO- and H2PO4-, with the ferrocene-based redox potential showing a large negative shift. Interestingly, both 1 and 2 exhibited an exclusive fluorescence sensing of F- over other anions, with the fluorescence of the receptors showing a turn-off response. Further, the binding mechanism between receptors and anions was confirmed by H-1 NMR titrations, which reveal that the two thiourea NH donors, cooperative with the amide donor, play a key role for binding the anions.