Selective metal-cation recognition by [2.2]ferrocenophanes: the cases of zinc- and lithium-sensing.

The synthesis, electrochemical, optical, and cation-sensing properties of [2.2]ferrocenophanes, in which the two ferrocene subunits are linked through two aldiminic or iminophosphorane moieties, are reported. The new compounds show remarkably selective cation-sensing properties due to the presence of redox-active units (ferrocene) and aza-unsaturated functionalities that are able to act as putative cation-binding sites.