Tripod-shaped penta (p-phenylene)s for the functionalization of silicon surfaces

TRIPOD-SHAPED PENTA (P-PHENYLENE)S FOR THE FUNCTIONALIZATION OF SILICON SURFACES María Sánchez-Molina, Rafael Contreras-Cáceres, Amelia Díaz, María Valpuesta and Juan M. López-Romero Department of Organic Chemistry, Faculty of Science, University of Málaga, Campus de Teatinos s/n, 29071 Málaga, Spain In order to obtain nanostructured thin films to be used in biosensor devices, several chemical functionalization methods have been developed, such as Click chemistry or Suzuki carbon-carbon coupling reactions on surfaces.1 With the aim to control the orientation and spacing between grafted functional groups on a surface, tripodal oligo (p-phenylene)s have become the ideal anisotropic adsorbates due to their shape-persistent and self-standing characteristics.2 Here we report the synthesis and characterization of several tripod-shaped oligo(pphenylene)s molecules with legs composed of five phenylene units, compounds 1, 2 and 3. In these structures, each leg is end-capped with an NH-Boc, NH2 and N3 group, respectively. The functional arm contains an acetylene group. The presented synthesis has as key step the Pd-catalyzed Suzuki cross-coupling reaction. In particular, a iodine derivative from the silicon core molecule reacts with the appropriate tetra(p-phenylene) boron derivative, thus generating the final tripod-shaped structure. The azide endcapped leg in 3 is specifically designed for its covalent incorporation on alkynyl terminated silicon surfaces by an easy and reproducible way. As a preliminary study, we present the alkynyl-functionalized silicon wafers nanostructuration with tripod 3 through the cooper catalyzed alkyne-azide cycloaddition (CuAAC) click reaction. [1] Wong, L. S.; Khan, F.; Micklefield, J. Chem. Rev., 2009, 109, 4025-4053. [2] López-Tocón, I.; Peláez, D.; Soto, J.; Rico, R.; Cai, C., López-Romero, J. M.; Otero, J. C., J. Phys. Chem. B 2008, 112, 5363-5367