The electrochemistry of self-assembled monolayers (SAMs) on gold containing a lipoic acid linker, the beta-peptide sequence (beta(3)Val-beta(3)Ala-beta(3)Leu)(n) for n = 1, 2, and a terminal ferrocenyl group has been described for the first time. Circular dichroism (CD), NMR, and molecular modeling were used to evaluate the beta-peptide structure in solution, while the monolayer film organization and electron-transfer kinetics were evaluated by cyclic voltammetry, chronoamperometry (CA), and ellipsometry. The peptides were assembled from trifluoroethanol solutions, where they are linear (n = 1) or helical (n = 2) based on CD, NMR, ellipsometry, and modeling evidence. The structure of the SAMs is less well understood. There is evidence for noncompact layers that allow electrolyte ions to approach the interface. Electron-transfer rates for n = 1, 2 were found to be 2500 and 1200 s(-1), respectively, and CA evidence indicated that the transfer is based on the hopping mechanism.

Here we report a versatile ring-closing metathesis-based approach to 5-, 6-, and 7-membered cyclic beta-amino esters starting with simple and readily available building blocks-methionine, allylglycine, and serine-where the nature of the amino acid determines the size of the carbocyclic ring.

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An investigation of the kinetics of electron transfer though a self-assembled monolayer containing long chain alkanethiol and β-peptide components and a terminating ferrocene group has been carried out at a polycrystalline gold electrode. Cyclic voltammetry and electrochemical impedance spectroscopy in aqueous and mixed aqueous−methanol solutions showed the rate of electron transfer varied from approximately 5 in water to 29 s−1 in methanol. This difference is attributed to a change in the alkanethiol tilt angle in the film in response to hydrogen bonding disruption of the peptide to allow greater molecular motion during electron transfer.