Photoelectron spectroscopy of catalytically important small ring mono-sulfur heterocycles adsorbed on a copper single crystal
Date Issued
December 1, 1980
Author(s)
Thomas, Terence Michael
Advisor(s)
Frederick A. Grimm
Additional Advisor(s)
Tom Carlson
Paul A. Agron
Bill Dress
Abstract
Photoelectron spectra using He(I) radiation are presented for Cu(110) after exposure to thiacyclobutane, thiacyclopentane and thiacyclohexane as well as for the clean (110) surface of copper at ambient temperatures. Analysis of the spectra of the adsorbates suggested a strong sulfur-to-copper-dative bond, though the strength of the bond varies from adsorbate to adsorbate. Sulfur lone pair orbital stabilization energies were obtained for thiacyclobutane (1.4 eV), thiacyclopentane (1.1 eV) and thiacyclohexane (0.6 eV) and these stabilization energies were correlated to the dative-sulfur-tosurface bond strength. Ring strain and/or geometry are suggested as reasons for additional small shifts of adsorbate bonds in the thiacyclobutane spectrum. Relaxation energies were found to decrease in the order 4 > 5 > 6 member ring. An empirical linear relation was found between relaxation energy shifts and lone pair orbital stabilization energies for mono-heteroatom heterocycles bonded to Cu(110) by a lone pair dative bond. All adsorbates studied showed marked angular dependence, suggesting nonrandom orientation of the adsorbates on the surface. Al Kα X-ray data were used to calculate percent surface coverage. Other sulfur containing adsorbates were also studied and discussed, including thiophene, allyl mercaptan and thiacyclopropane. Thiacyclopropane was found to decompose upon exposure to copper.
Degree
Doctor of Philosophy
Major
Chemistry
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Thesis80b.T465.pdf
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