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Issue 45, 2010
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Molecular structures of dicarboxylated viologens on a Cu(100) surface during an ongoing charge transfer reaction

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Abstract

Molecular structures of dicarboxylated viologens (1,1′-bis (7-carboxyheptyl)-4,4′-bipyridinium dibromide molecules, V-(C7–COOH)2) on a Cu(100) surface are studied by means of in situ scanning tunneling microscopy (STM) in combination with cyclic voltammetry (CV). Self-assembled monolayers of adsorbed dicarboxylated viologens form during an ongoing charge transfer reaction. Mainly six structures of the organic molecules are observed, including a dot array, metastable phases, stripe patterns, a closed stacking stripe pattern, chloride desorption, and a dimer phase. The molecular structural models for all the structures have been successfully established. The carboxylated viologen molecules in the dicationic state prefer the face-on configuration on the surface and form the dot array phase. The other phases are shown by the radical state of the viologens. The metastable phases show two forms: cluster-like and stripe pattern-like structures. Main features of the metastable phases are face-to-face configurations of the radical viologens in π-stacking form between neighboring parallel bipyridiniums. Hydrogen bonding is considered to be the major factor in constructing the network of the stripe pattern. At a more negative potential, the bilayers of the stripe pattern transform to be a monolayer of the closed stacking stripe pattern because of the enhanced electrostatic force. The closed stacking stripe pattern is stable on the surface until chloride desorption. As the chloride anions desorb from the Cu(100) surface, the disordered dimers transform to an ordered dimer phase on a Cu(100)-1×1 surface due to the hydrogen bonding between neighboring dimer rows.

Graphical abstract: Molecular structures of dicarboxylated viologens on a Cu(100) surface during an ongoing charge transfer reaction

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Publication details

The article was received on 12 Jun 2010, accepted on 06 Aug 2010 and first published on 15 Oct 2010


Article type: Paper
DOI: 10.1039/C0CP00865F
Citation: Phys. Chem. Chem. Phys., 2010,12, 14950-14959
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    Molecular structures of dicarboxylated viologens on a Cu(100) surface during an ongoing charge transfer reaction

    S. Tsay, J. Tsay, T. Fu, P. Broekmann, T. Sagara and K. Wandelt, Phys. Chem. Chem. Phys., 2010, 12, 14950
    DOI: 10.1039/C0CP00865F

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