Coordination and bonding geometry of nitromethane (CH3NO2) on Au(111) surfaces

Jiang Wang, Harald Busse, Denis Syomin, Bruce E. Koel

Research output: Contribution to journalArticle

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Abstract

The adsorption and bonding geometry of nitromethane (CH3NO2) on a Au(111) single crystal surface was studied by temperature programmed desorption and infrared reflection-absorption spectroscopy (IRAS). Nitromethane weakly adsorbs on Au(111) with an adsorption energy of only 10.5 kcal/mol. Adsorption is completely reversible; no thermal decomposition occurs under UHV conditions. Consistent with weak binding, IRAS does not reveal any significant chemical shifts for the vibrational modes of CH3NO2 at monolayer and submonolayer coverages compared to solid multilayer films. Based on the intensities in IRAS and the surface selection rule, we propose that CH3NO2 adsorbs on the Au(111) surface with Cs symmetry in a monodentate geometry using one oxygen atom to bind to the surface with a large tilt of the C-N bond away from the surface normal. This bonding interaction is 25% less than that of adsorbed NO2 on Au(111) which chemisorbs in an O,O′-chelating geometry with C2v symmetry. While isomerization of nitromethane to from methyl nitrite (CH3NO2↔CH3ONO) occurs during thermal decomposition in the gas phase, the Au(111) surface does not sufficiently activate CH3NO2 for dissociation or isomerization to occur under UHV conditions, and so the activation energies for these processes exceed 10.5 kcal/mol on Au(111).

Original languageEnglish (US)
Pages (from-to)L741-L747
JournalSurface Science
Volume494
Issue number1
DOIs
StatePublished - Nov 10 2001
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Surfaces, Coatings and Films
  • Materials Chemistry

Keywords

  • Gold
  • Infrared absorption spectroscopy
  • Thermal desorption
  • Vibrations of adsorbed molecules

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