Redox induced orientational changes in a series of short chain ferrocenyl alkyl thiols self-assembled on gold(111) electrodes

A series of short chain alkyl thiols (n=3–10) with a ferrocene terminal group were allowed to form organised monolayers at gold(111) surfaces. The redox activity of the monolayers was monitored using cyclic voltammetry and subtractively normalised interfacial Fourier transform infrared spectroscopy (SNIFTIRS). The in situ infrared spectra show that the oxidation of the ferrocene groups in the monolayers studied is accompanied by a rotation of the ferrocene groups towards a position where the plane of the cyclopentadienyl rings moves to a position normal to the surface of the electrode. Furthermore, electrochemical and spectroscopic data indicate that monolayers with longer alkyl chains are more ordered than the shorter analogues. A trend was observed in which the rate of adsorption and the surface coverage vary between the length of the alkyl chains.