Facile Convergent Route to Molecular Caltrops.

The convergent syntheses of molecular caltrops are described starting from tetraethyl orthosilicate and using organolithium additions and Pd/Cu-catalyzed coupling methods. The caltrop core is based on a tetrahedral silicon atom, and there are three legs each bearing sulfur-tipped feet for adhesion to metallic surfaces. The forth prong (arm) is non-sulfur-bearing for projection upward from the surface. Rigid phenyleneethynylene segments are used for the legs and arms. These organosilicon caltrops may have utility as scanning probe microscopy tips.