Structural effects in electron transfer reactions: comparative interfacial electrochemical kinetics for cis- versus trans-dioxorhenium(V)(bi)pyridine oxidation

Xiao Lian Zhang, Joseph T. Hupp, Gerald D. Danzer

Research output: Contribution to journalArticle

2 Citations (Scopus)

Abstract

The comparative interfacial oxidation kinetics of the approximate structural isomers trans-(O)2ReV(py)+4 and cis-(O)2ReV(bpy)(py)+2 (py, pyridine; bpy, 2,2′-bipyridine) have been assessed in aqueous solution via conventional cyclic voltammetry at a highly ordered pyrolytic graphite (HOPG) electrode. HOPG was employed because of its known propensity to diminish interfacial electron transfer (ET) rates (by ca. three to four orders of magnitude) and because of a probable lack of importance of kinetic work terms (diffuse double-layer corrections). Measured rates for the trans complex exceed those for the cis by about a factor of 3. Expressed as an effective activation Gibbs energy difference ΔG*, this corresponds to a cis-trans difference of ca. 3 kJ mol-1. The actual vibrational barriers to ET have determined from a combination of published X-ray structural results (trans complex) and new resonance Raman results (cis complex). The values are 0.6 kJ mol -1 for the trans oxidation and 4.4 kJ mol-1 for the cis oxidation (i.e. close to the barrier difference inferred from rate measurements). Further analysis shows that most of the barrier difference is associated with displacement of a (predominantly) Re-N(bpy) stretching mode found only in the cis system. Differences in metal-oxo displacements (cis > trans) are also implicated.

Original languageEnglish
Pages (from-to)229-235
Number of pages7
JournalJournal of Electroanalytical Chemistry
Volume380
Issue number1-2
DOIs
Publication statusPublished - Jan 3 1995

Keywords

  • Dioxorhenium(V)(bi)pyridine
  • Electron transfer reactions
  • Interfacial oxidation kinetics
  • Structural effects

ASJC Scopus subject areas

  • Analytical Chemistry
  • Chemical Engineering(all)
  • Electrochemistry

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