Installation d'un systeme FT-IRRAS et son application a l'etude de l'adsorption de molecules sur le Ni(111) (French and English text)

The objective of this thesis was to put in place an infrared reflection-absorption spectrometer for the study of the adsorption of organic molecules on Ni(111). The spectrometer was successfully put in place and it has been used for the study of the adsorption geometry and conformation of methyl pyruvate and tert-butyl formate on Ni(111), as well as for the study of their chemical behaviour.; No cis-trans isomerization of tert-butyl formate was observed as a function of the coverage of the Ni(111) surface. This behaviour differs from what was previously observed in this laboratory in the case of methyl and ethyl formate. This difference has been explained in the terms of the larger tert-butyl group for which the van der Waals interactions with the surface are particularly favourable for a molecule adsorbed in the cis conformation. Therefore, these results indicate that intermolecular interactions which arise as coverage increases are not sufficient for the modification of the higher stability of the cis isomer, the latter being able of a better surface- tert-butyl interaction than that possible for trans adsorbed molecule. tert-butyl formate decomposes through successive steps on Ni(111) which produce tert-butoxy and tert-butyl intermediates. The latter is stabilised by co-adsorbed carbon monoxide, a product of the surface molecular decomposition.; We have also realised the first surface spectroscopic study of methyl pyruvate. At low coverages, there is a mixture of cis and trans isomers whereas the full monolayer contains only the cis isomer. The molecule is adsorbed perpendicular to the surface through the ketone oxygen in the case of the trans isomer and through both oxygen atoms from the carbonyl groups in the case of the cis isomer. We have presented a discussion on the significance of these results with respect to the enantioselective catalytic hydrogenation of methyl pyruvate. Upon decomposition on Ni(111) methyl pyruvate produces, among others, adsorbed methoxycarbonyl for which this is the first identification on a solid surface.