A bis(ferrocenyl)phenanthroline iridium(III) complex as a lab-on-a-molecule for cyanide and fluoride in aqueous solution

The bis(ferrocenyl)phenanthroline iridium(III) complex 1 is synthesized and elaborated as a lab-on-a-molecule for the competitive and quantitative determination of cyanide and fluoride in aqueous solution. 1 exhibits a strong OFF-ON photoluminescence (PL) response upon addition of cyanide with a good selectivity over other anions. The mechanism involves nucleophilic displacement of the phenanthroline ligand, which quenches PL, to furnish a strongly photoluminescent dicyano iridium complex. In contrast, in the electrochemiluminescence (ECL) channel, cyanide undergoes oxidation and a different selectivity is observed. The strong ferrocenium-fluoride interaction is exploited for the first time in ECL to selectively monitor fluoride by a >60-fold enhancement. In both PL and ECL channels, anion selectivity is further challenged by competitive assays in the presence of other anions. Quantitative determination of CN^- and F^- is achieved in both channels.