Orthogonally fused conducting oligomers for molecular electronic devices

Described is the synthesis of two spiro core segments of orthogonally arranged conducting systems and the adhesion of oligomeric branching units to the core segments. The final systems are to have a potentially conducting chain fused perpendicularly to a second potentially conducting chain via a sigma bonded network. These systems may be suitable for incorporation into future molecular electronic devices. One of the core segments synthesized is based on a thiophene conducting group and it is formed by a zirconium‐promoted bis(bicyclization) of bis(diyne) systems. The second is a phenylene‐based system that is derived from fluorene. Terminal bromide groups provide the linkage points for further extensions of the chains via palladium‐catalyzed cross coupling methods. Four thiophene trimers are added in a single operation to spiro‐fused cores to afford the target molecules. A spiro‐fused thiophene‐based monomer system is converted to a spiro‐fused heptamer that is 25 Å long. The synthesis of a mixed phenylene‐thiphene system is described that provides a spiro‐fuled octamer that is 30 Å long. In each case, alkyl substituents on the thiophenes afford soluble materials. Trimethylsilyl end groups flank each orthogonally fused system. Organopalladium‐ and organonickel‐catalyzed procedures are used extensively for the synthesis of the orthogonally fused compounds.