Functionalized silanes for the preparation of siloxane-anchored monolayers

Siloxane-anchored monolayer films are best prepared by the self-assembly of trichlorosilanes. The moisture sensitivity and chemical reactivity of the trichlorosilane moiety complicates the synthesis and purification of the ω-functionalized alkyltrichlorosilanes that are the building blocks for functionalized monolayer surfaces. Obtaining these materials is facilitated by using trialkoxysilanes as synthetic intermediates. They offer superior stability with respect to various synthetic operations. This allows the flexibility to incorporate the silane functionality at various stages of a multistep synthesis. This relative stability has also allowed us to develop a general approach to their purification by chromatography (using Si(OCH₃)₄ as an additive), making them useful in removing undesired side products. Ultimately, the usefulness of the alkoxysilanes is also evidenced in the ease with which they can be converted into the trichlorosilanes, as needed for monolayer self-assembly. Trichloroacetyl chloride has proven to be the optimal reagent for this transformation.