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

Sung Lin Tsay, Jyh Shen Tsay*, Tsu Yi Fu, Peter Broekmann, Takamasa Sagara, Klaus Wandelt

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

19 Citations (Scopus)


Molecular structures of dicarboxylated viologens (1,1′-bis (7-carboxyheptyl)-4,4′-bipyridinium dibromide molecules, V-(C 7-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.

Original languageEnglish
Pages (from-to)14950-14959
Number of pages10
JournalPhysical Chemistry Chemical Physics
Issue number45
Publication statusPublished - 2010 Dec 7

ASJC Scopus subject areas

  • General Physics and Astronomy
  • Physical and Theoretical Chemistry


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