Surface Inorganic Chemistry: The Reaction of Hydroxyl-Terminated Thiols on Gold with a Zirconium Coordination Compound

We produced a well-defined inorganic/organic double layer system by the reaction of a zirconium coordination compound with a hydroxyl-terminated alkanethiol monolayer. The hybrid system was prepared by wet chemistry, immersing a thiol-covered gold substrate in a dilute solution of the reagent bis(acetylacetonato)bis(1,1,1,3,3,3-hexafluoro2-propanolato)zirconium, Zr(acac)(2)(hfip)(2), in isooctane. Characterization of the layered structure was carried out by means of contact-angle measurements, X-ray photoelectron spectroscopy, and mass spectroscopy. The inorganic compound was found to establish a monolayer on top of the supporting organic film, with a packing density of approximately 1 order of magnitude lower than the underlying thiol film. The rate constant of the reaction was found to be significantly lower than that of thiol adsorption on gold. While the films were stable under hexane and isooctane, the reaction of the zirconium reagent with the surface-immobilized alcohol was completely reversible when immersed in ethanol. In contrast to hydroxyl-terminated films, methyl-terminated alkanethiol films showed complete inertness to the Zr reagent solution.