Structure and redox behavior of azobenzene-containing monolayers on Au(1 1 1): A combined STM, X-ray reflectivity, and voltammetry study

A combined structural and electrochemical study of self-assembled monolayers of the azobenzene-containing alkane thiol N-(2-mercaptoethyl)-4-phenylazobenzamide on Au(1 1 1) by scanning tunneling microscopy, synchrotron X-ray reflectivity, and cyclic voltammetry is presented. Densely packed monolayers are observed, in which the molecules are arranged in chains forming an ordered ( 13 × 3 ) structure with a coverage of 2/7 ML. The molecules are tilted by 40° relative to the surface normal, resulting in a monolayer thickness of 13.7 Å. A total charge of 65.2 ± 4.3 μC/cm2 corresponding to 1e− per molecule and apparent electron transfer coefficients of ≈0.5 are found.