Synthesis and electrochemical characterization of novel bridged diferrocene tagged alkanethiol self-assembled monolayers /

Abstract

A diferrocene tagged alkanethiol monolayer was synthesized via a four part reaction procedure to produce 6-(diferrocenylhexanylcarbonyl)pentanethiol. Monolayers were adsorbed onto a polycrystalline gold electrode by soaking in a solution of the thiol. Cyclic voltammetric experiments were done to determine the heterogeneous electron transfer rate constant, kO. Formal potentials, surface coverages and FWHM values were investigated to determine the thermodynamic properties of the thiol monolayer. Single crystal X-ray crystallography was performed on three compounds synthesized throughout the reaction pathway. These experiments provided information regarding symmetry and unit cell packing of the molecules, as well as the relative positions of the ferrocenes with respect to one another. This research provides preliminary voltammetric data on alkanethiol monolayers tagged with dimeric ferrocenes. Introduction of another electroactive moiety within the monolayer can dramatically alter the shape of the voltammograms. Formal potentials, FWHM data and electrochemical kinetics were similar to those reported in the literature. Analysis of surface coverages indicates that only 40% of the outer ferrocenes are electrochemically accessible. A possible explanation for this unusual phenomenon is suggested.