Potential dependent change in local structure of ferrocenyl-terminated molecular islands by electrochemical frequency modulation atomic force microscopy

Electroactive ferrocenylundecanethiol $(FcC11H22SH)$ islands embedded in a $n$-heptanethiol $(C7H15SH)$ self-assembled monolayer matrix on Au(111) were studied under potential control in $0.1M$ $HClO4$ aqueous solution using electrochemical frequency modulation atomic force microscopy. Signal of local structural change on the $Fc$ islands upon oxidation from $Fc0$ to $Fc+$ was obtained in topography as a reversible process; however, the magnitude of the change was far less than expected in contrast to the case of the previous study for $FcC11H22SH$ islands embedded in $C10H21SH$⁠. Different degrees of freedom for the structures of the $Fc$ islands originating from different molecular lengths for surrounding matrix molecules perhaps provide the distinct contrast between the two systems.