Electrochemically controlled 2D assembly of paddle-wheel diruthenium complexes on the Au(111) surface and identification of their redox states

The 2D molecular assemblies of chloride-coordinated mixedvalence diruthenium complexes, each possessing phenyl, naphtyl, or anthracenyl moieties, were examined on an Au(111) at electrochemical interface. In situ scanning tunneling microscopy images revealed a clear dependence of the molecular assembly on both the nature of the aryl functional groups and on the redox state of the dinuclear ruthenium complex, either chloride-coordinated Ru ^II/Ru ^III or noncoordinated Ru ^II/Ru ^II. At potentials where the Ru ^II/Ru ^III and Ru ^II/Ru ^II redox states were in equilibrium, two distinct redox states were clearly identified at the single-molecular level. We found that manipulating both the electrochemical potential and the aryl functional group substitution was important for controlling the 2D molecular assembly of a chloride-coordinated diruthenium complex on an Au(111) surface.