Design, synthesis and anion recognition of ferrocene-based benzimidazolium receptors

• Receptors 4–7 are characterized by single-crystal X-ray diffraction analysis.
• Receptors 4–7 have selectivity for F− in the electrochemical behaviors.
• Receptors 6 and 7 have selectivity for F− on the UV–visible absorption studies.
• Receptors 4–7 have a good fluoride binding ability in DMSO-d6.
• Ferrocene-based benzimidazolium fragment linked to conjugated group 6 and 7 exhibit better affinity for F−.

A series of novel ferrocene-based benzimidazolium receptors 4–7 were designed and structurally characterized, their crystal structures revealed that these receptors were capable of incorporating anions such as PF6− and Br− and that the molecules were linked by C–H···X hydrogen bonds. The anion binding studies were carried out using various techniques including electrochemistry (CV and SWV), UV–vis and 1H NMR spectroscopy. Electrochemical behavior indicated that all the receptors displayed rather strong electrochemical sensing properties for F− in CH3CN. For receptors 6 and 7, obvious absorption changes were observed when F− was added in CH3CN on the UV–vis spectra. 1H NMR titrations demonstrated that all the receptors could bind anions through (C–H)+···X− hydrogen bonds forming 1:1 stoichiometric complexes and have good fluoride binding ability in DMSO-d6. The anion binding studies indicated that receptors 6 and 7 comprised of the ferrocene-based benzimidazolium fragment and conjugated group showing better affinity for F− than receptors 4 and 5.

The receptors comprising of ferrocenyl unit and benzimidazolium moiety were synthesized and structurally charecterized. The anion binding studies were carried out using electrochemistry, UV-vis and 1H NMR spectroscopy, which indicated receptors comprised of the conjugated group and a redox unit showed better affinity for anion.Figure optionsDownload as PowerPoint slide