Ferrocenyl alkanethiols-thio beta-cyclodextrin mixed self-assembled monolayers: evidence of ferrocene electron shuttling through the beta-cyclodextrin cavity.

This paper reports the preparation and characterization of an Au electrode modified with self-assembled alkane ferrocenes, in the absence and in the presence of beta-cyclodextrins (betaCD). Electrode modification with ferrocene derivatives was achieved through a self-assembled monolayer (SAM) approach, using ferrocenyl hexane thiol (FcC6) and ferrocenyl undecane thiol (FcC11); the same was also done using per-6-thio-beta-cyclodextrin. The different SAMs prepared were characterized by both cyclic voltammetry and electrochemical surface plasmon resonance (EC-SPR). The behavior of both single and binary monolayers including their interfacial reorganization was investigated and critically discussed, according to the nature of the SAM used. Cyclic voltammetry combined with SPR measurements revealed the reorientation of the SAM concomitant with the oxidation of ferrocene moieties. In particular, the electron shuttling of FcC11 through the betaCD cavity (mixed SAM) was also evidenced by both SPR and the electrocatalytic oxidation of ferro(II)cyanide.