CONVERGENT SYNTHETIC ROUTES TO ORTHOGONALLY FUSED CONJUGATED OLIGOMERS DIRECTED TOWARD MOLECULAR SCALE ELECTRONIC DEVICE APPLICATIONS

This paper describes the synthetic organic phase of a project directed toward the construction of molecular scale electronic devices. Outlin ed is a convergent synthetic route to orthogonally fused conjugated or ganic oligomers. The final systems are to have a potentially conductin g chain fused perpendicularly to a second potentially conducting chain via a sigma bonded network. One of the core segments synthesized is b ased on a spirobithiophene moiety with a central silicon atom. It is f ormed by a zirconium-promoted bis(bicyclization) of a tetrapropargylsi lane. The second core is a 9,9'-spirobifluorene system. Terminal halid e groups provide the linkage points for further extension of the chain s via Pd-catalyzed or Pd/Cu-catalyzed cross coupling methods. AU four branching ams are affixed to the core in a single operation, thus maki ng the syntheses highly convergent. In the cases of the larger functio nalized systems, alkyl substituents on the thiophenes afford soluble m aterials. In order to prepare the molecules with >50 Angstrom lengths, an iterative divergent/convergent approach had to be utilized for the construction of oligo(thiophene-ethynylene) branching arms. Organopal ladium-catalyzed procedures are used extensively for the syntheses of the orthogonally fused compounds.