Semiconductor Surface-Induced 1,3-Hydrogen Shift: The Role of Covalent vs Zwitterionic Character

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• 作者：Michael P. Schwartz ; Daniel E. Barlow ; John N. Russell ; Jr. ; Kevin P. Weidkamp ; James E. Butler ; Mark P. D'Evelyn ; Robert J. Hamers
• 刊名：Journal of the American Chemical Society
• 出版年：2006
• 出版时间：August 30, 2006
• 年：2006
• 卷：128
• 期：34
• 页码：11054 - 11061
• 全文大小：133K
• 年卷期：v.128,no.34(August 30, 2006)
• ISSN：1520-5126

文摘

X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR)are used to compare the reaction of 1,2-cyclohexanedione (1,2-CHD) with Si(001) and diamond(001) surfacedimers under ultra-high-vacuum conditions. 1,2-CHD is known to undergo a keto-enol tautomerization,with the monoenol being the primary equilibrium species in the solid and gas phases. XPS and FTIR datademonstrate that 1,2-CHD reacts with diamond(001) through the OH group of the monoenol, resulting inonly one O atom being bonded to the surface. In contrast, XPS and FTIR data suggest that both oxygenatoms in the 1,2-CHD molecule bond via Si-O-C linkages to the Si(001) surface dimer, and that themolecule undergoes an intramolecular 1,3-H shift. While the Si(001) and diamond(001) surfaces are bothcomprised of surface dimers, the diamond(001) dimer is symmetric, with little charge separation, whereasthe Si(001) dimer is tilted and exhibits zwitterionic character. The different reaction products that are observedwhen clean Si(001) and diamond(001) surfaces are exposed to 1,2-CHD demonstrate the importance ofcharge separation in promoting a 1,3-H shift and provide new mechanistic insights that may be applicableto a variety of organic reactions.