STM contrast, electron-transfer chemistry, and conduction in molecules

Wenhai Han, Edgardo N. Durantini, Thomas Moore, Ana Moore, Devens Gust, Peter Rez, Gerald Leatherman, Gilbert R. Seely, Nongjian Tao, Stuart Lindsay

Research output: Contribution to journalArticlepeer-review

137 Scopus citations


We have used a series of metalloporphyrin compounds to test for a relationship between the contrast of STM images and the electrochemical properties of the molecules. Molecules were tethered to a gold (111) surface by means of an isothiocyano linkage and both images and current-voltage (I-V) curves were obtained with the sample submerged in oxygen-free mesitylene. The contrast of the reducible molecules changed strongly with bias, and the corresponding I-V curves were highly asymmetric. The derivative of these curves (dI/dV) had a Gaussian-shaped peak at a voltage characteristic of the compound, although local measurements showed that there was considerable variation in this value from molecule to molecule of a given compound. These bias-dependent features were not observed in the less electroactive molecules, so the STM is capable of distinguishing electroactive molecules from non-electroactive molecules as we demonstrate with images of mixed films. We discuss one- and two-step electron-transfer mechanisms which are consistent with these observations.

Original languageEnglish (US)
Pages (from-to)10719-10725
Number of pages7
JournalJournal of Physical Chemistry B
Issue number50
StatePublished - Dec 11 1997

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films
  • Materials Chemistry


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