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

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

Research output: Contribution to journalArticlepeer-review

132 Citations (Scopus)


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
Pages (from-to)10719-10725
Number of pages7
JournalJournal of Physical Chemistry B
Issue number50
Publication statusPublished - Dec 11 1997

ASJC Scopus subject areas

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

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