Polyalanine derivatives containing cysteamine linker R-(Ala)14NH-(CH2)2-SH, where R is ferrocenecarbonyl or hydrogen, were synthesized and then used to form self-assembled monolayers on gold. The tilt angles and the packing density of the molecules within monolayer assemblies were determined by FTIR spectroscopy and scanning tunneling microscopy, respectively. Electrochemical properties of monolayer-modified electrodes were studied using cyclic voltammetry and impedance spectroscopy. Measurements of electron-transfer rates using electrochemical techniques and scanning tunneling spectroscopy revealed asymmetry dependent on the applied voltage. It is suggested that the observed electron-transfer behavior is connected with the electric field generated by the molecular dipole of the polyalanine helix.

A series of oligoglycine derivatives (Fc−CO(Gly) n NH−(CH2)2−SH (where Fc = ferrocene; Gly = glycine; n = 2−6) were synthesized and then self-assembled on gold in the presence of selected alkanethiols in order to form mixed monolayers. The properties and electron transfer behavior of the monolayer assemblies were investigated using electrochemical methods. It was found that the rates of electron transfer through oligoglycine bridges decrease rapidly with distance only for short chain derivatives, while for the longer bridges the distance dependence is weaker. Differences in the secondary structure of the peptide bridges and the change of the electron transfer mechanism are considered as possible reasons of the increase of the rate constants observed for the longer peptide chains.