AVS 47th International Symposium
    Organic Films and Devices Wednesday Sessions
       Session OF-WeA

Paper OF-WeA7
Generation of Reactive Intermediates on Platinum by Photolysis of Pyridyl-@alpha@-Diazocarbonyl Self Assembled Monolayers

Wednesday, October 4, 2000, 4:00 pm, Room 313

Session: Self-Assembled Monolayers: Electron Transfer and Film Properties
Presenter: J.L. Pitters, University of Western Ontario, Canada
Authors: J.L. Pitters, University of Western Ontario, Canada
D.K. Adkinson, University of Western Ontario, Canada
P.R. Norton, University of Western Ontario, Canada
M.S. Workentin, University of Western Ontario, Canada
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There is considerable current interest in understanding the chemistry of organic molecules as Self Assembled Monolayers (SAMs) on metal surfaces. Much of the effort in this regard has focused on long chain alkyl thiols on gold with the ultimate goal of being able to control the interfacial properties for use in wide ranging material and device applications. However, there has been a growing interest in small molecule SAMs and their relevance to surface modification. We have prepared a series of photoreactive pyridine based molecules for study as SAMs on single crystal Pt. Monolayers (saturated layers) of pyridyl-diazoketones, pyridyl-diazoesters and pyridyl-diazoaldehydes have been characterized using Ultra High Vacuum (UHV) Reflection Absorption Infrared Spectroscopy (RAIRS) and other surface sensitive techniques. Diagnostic out-of-phase C=N=N and C=O absorptions indicate that the diazo and carbonyl groups are stable on the Pt surface and that binding most likely takes place through the pyridyl nitrogen as is the case in most substituted pyridines. Upon exposure to 300-400 nm light, the diazo group releases nitrogen quantitatively to yield either carbene or ketene intermediates depending on the original substrate. Most notably is the formation of a ketene functionality (C=C=O) at the interface through the Photo-Wolff rearrangement. The ketene is identified by the diagnostic out-of-phase infrared absorption at approximately 2110 wavenumbers. This study represents the first direct spectroscopic evidence of a photoreactive diazo-carbonyl monolayer and the subsequent photochemical formation of a stable ketene monolayer on a metal surface. Ketene and carbene reactivity is versatile and we believe that knowledge of the interfacial reactivity in the present systems can be extended to provide a novel surface for template synthesis and surface modification.