Ferrocene-based imidazolium receptors for anions

Cyclic and acyclic ferrocene derivatives bearing two imidazolium rings have been synthesized and characterized by NMR, elemental analysis, mass spectra, and X-ray crystallography. Electrochemical measurements revealed that all the receptors displayed a significant anodic shift response for F−. In addition, for receptors 1, 2, and 4, addition of HSO4− induced quite different electrochemical behavior with dramatic cathodic peak current increase on CV. 1H NMR titrations demonstrated that receptors 1, 2, and 4 showed selectivity for AcO− while receptor 3 exhibited high affinity toward Cl− among the anions investigated.