AND/NOT sensing of fluoride and cyanide ions by ferrocene-derivatised Lewis acids

A simple two-component sensor system was developed, featuring the strongly Lewis acidic (but air-stable) FcRBMes2 (1: FcR=(η5-C5H4)Fe(η5-C5R5), R=H, Me; Mes=2,4,6-Me3C6H2), which can be shown to bind both fluoride AND cyanide in solution (but not other anions), and the weaker boronic ester Lewis acid FcRB(OR)2 (2: (OR)2=R,R-OC(H)PhC(H)PhO), which signals the presence of fluoride but NOT cyanide in solution. By coupling the electrochemical shifts with a suitable redox-active tetrazolium dye, a colorimetric AND/NOT sensor system for fluoride and cyanide ions can be develope