A Halogen Bonding 1,3-Disubstituted Ferrocene Receptor for Recognition and Redox Sensing of Azide

Abstract

A neutral redox-active acyclic halogen bonding (XB) receptor with a ferrocene core functionalised at the 1,3-positions of a cyclopentadienyl ring with iodotriazole motifs is prepared. Owing to favourable host-guest size-complementarity, the receptor was found to be selective for azide over a diverse range of anions with different geometries. Voltammetric studies revealed the unique ability of the XB ferrocene receptor to selectively sense azide via a significant cathodic shift of its ferrocene/ferrocenium redox couple. Notably, much weaker binding of azide was observed for the hydrogen bonding 1,3-bis-prototriazole ferrocene receptor analogue, which also displayed a poorer electrochemical response, suggesting that halogen bonding interactions play crucial roles in the binding and sensing of azide.