Neutral redox-active hydrogen- and halogen-bonding [2]rotaxanes for the electrochemical sensing of chloride

The first examples of redox-active ferrocene-functionalised neutral [2]rotaxanes have been synthesised via chloride anion templation. (1)H NMR spectroscopic titrations reveal that these [2]rotaxane host systems recognize chloride selectively over other halides and oxoanions in highly-competitive aqueous media. By replacing the hydrogen bonding prototriazole units of the rotaxane axle component with iodotriazole halogen bond-donor groups, the degree of chloride selectivity of the [2]rotaxanes is modulated. Electrochemical voltammetric experiments demonstrate that the rotaxanes can sense chloride via cathodic perturbations of the respective rotaxanes' ferrocene-ferrocenium redox-couple upon anion addition.