Abstract

  We overview recent investigations of structure and electronic function of single transition metal complexes and redox metalloprotein molecules, mapped by electrochemical scanning tunneling (ECTM) and atomic force microscopy (ECAFM). A spectroscopic feature in the tunneling current-overpotential correlations is caused by population/depopulation of the molecule redox levels. Bandshape details are determined by the electrochemical potential, bias voltage, ionic strength etc. in the tunneling gap. The degree of electronic coherence in the overall two-step conduction process is determined by the coupling between the redox group and the enclosing electrodes which strongly affects the number of electrons transferred in a single-two-step ECST event. This pattern is illustrated by s-polypyridine complexes and the bacterial heme protein cyt b562.

  Molecular size metallic nanoparticles, AuNPs in particular are long known to act as efficient catalysts of interfacial electrochemical ET. AuNP catalysis of gas phase reactions of small molecules is understood in some detail but these notions cannot be transformed straightforwardly to the much more complex electrochemical interface. We investigate here to which extent single-molecule electrochemical and ECTM notions can be transferred to molecular size metallic NPs and offer a view towards the way the molecular scale metallic NPs may operate in simple electrochemical ET processes based on the electronic properties of the particles.

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