Electron transfer through organic monolayer films with oligoglycine spacers

Self-assembled monolayers were designed as model systems for the investigation of electron transfer mediated by peptide chains. A thiol derivative containing a cysteamine linker, four glycine residues and a ferrocene head group—Fc-(CO)-(Gly)4-NH-(CH2)2-SH, was synthesized and used for preparation of monolayer assemblies. Electrochemical methods were employed to measure the electron transfer rates through one-component oligoglycine monolayers and through mixed monolayers with oligoglycine molecules (0.2–0.5%) embedded in the alkanethiol matrix. The standard rate constant for electron tunneling through the pure oligolglycine monolayer (821±78 s−1) is larger than that through the mixed monolayer with alkanethiols as the main component (36±7 s−1) and larger than for the corresponding alkanethiol monolayer (12 s−1).