Dresden 2011 – scientific programme

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O: Fachverband Oberflächenphysik

O 53: Solid / liquid interfaces III

O 53.1: Talk

Wednesday, March 16, 2011, 15:00–15:15, WIL C107

The adsorption and in situ characterization of viologen monolayers at copper/electrolyte interfaces. — •Emilia Sak¹, Ralf Troff², Christoph Schalley², and Klaus Wandelt¹ — ¹Institute of Physical and Theoretical Chemistry, University of Bonn, Wegelerstr.12, 53115 Bonn, Germany — ²Institute Chemistry and Biochemistry, Free University of Berlin, Takustr.3, 14195 Berlin, Germany

Different redox-active 1,1’-Dibenzyl-4,4’-bipyridinium (or "viologen") molecules (DBV) adsorbed on a chloride - modified Cu(100) electrode have been studied by means of cyclic voltammetry (CV) and in-situ scanning tunneling microscopy (STM). At anodic potentials unsubstituted DBV forms a laterally well ordered quadratic array of dicationic "cavitand" ensembles which at negative potentials transformes into a stripe phase of π-stacked monocation radicals. Likewise with Dimethyl-DBV (DMDBV) a pair of redox peaks P1/P1’ (-305 mV / -240 mV) is found which is accompanied by a transition form a "cavitand" to a dimer phase. Quite in contrast, Tetrametyl-DBV (TMDBV) does not show redox peaks in CV and, accordingly, only a "cavitand" phase. Also the adsorption kinetics of all three molecules is significantly different, it slows down with increasing methylation.