Unusual electrochemical properties of the inclusion complexes of ferrocenium and cobaltocenium with cucurbit[7]uril

Ferrocenium and cobaltocenium form highly stable 1:1 inclusion complexes with the host cucurbit[7]-uril. From electronic absorption spectroscopic data the association equilibrium constants for both complexes were found to be larger than 10(6) L/mol. The electrochemical reduction of either guest leads to a modest loss in binding affinity.