Jeffry S. Schumm

Approaches to Orthogonally Fused Conducting Polymers For Molecular Electronics

Molecular electronics-based computing instruments possess tremendous technological potential. There is the hope of developing single molecules that could each function as a self-contained electronic device. Thus, one can envision computing systems with molecular-sized electronic elements and operational efficiencies far exceeding that of present systems.3 Recently, Aviram of the IBM Corporation has suggested that molecules which contain a pro-conducting (non-doped or non-oxidized system, hence insulating) polymer which is fixed at a 90° angle via a non-conjugated sigma bonded network to a conducting (doped or oxidized system) should exhibit properties which would make it suitable for interconnection into future molecular electronic devices.4 These devices may be useful for the memory, logic, and amplification computing systems. The molecule 1 (in doped form) is an example of this pro-conducting/sigma/conducting type of molecule.

Potential molecular wires and molecular alligator clips

The synthesis of oligo(2-ethylphenylene-ethynylene)s, oligo(2-(-ethylheptyl)phenylene-ethynylene)s, and oligo(3-ethylthiophene-ethynylene)s is described via an iterative divergent convergent approach. Synthesized were the monomer, dimer, tetramer, octamer and 16-mer of the oligo(3-ethylthiophene-ethynylene)s and oligo(2--ethylheptyl)phenylene-ethynylene)s. The 16-mers are 100 A and 128 A long, respectively. At each stage in the iteration, the length of the framework doubles. Only three sets of reaction conditions are needed for the entire iterative synthetic sequence; an iodination, a protodesilylation, and a Pd/Cu-catalyzed cross coupling. The oligomers were characterized spectroscopically and by mass spectrometry. The optical properties are presented which show the stage of optical absorbance saturation. The size exclusion chromatography values for the number average weights, relative to polystyrene, illustrate the tremendous differences in the hydrodynamic volume of these rigid rod oligomers versus the random coils of polystyrene. These differences become quite apparent at the octamer stage. The preparation of thiol-protected end groups is described. These may serve as molecular alligator clips for adhesion to gold surfaces. These oligomers may act as molecular wires in molecular electronic devices and they also serve as useful models for understanding related bulk polymers.

Molecular scale electronics. Syntheses and Testing

The syntheses of conjugated molecules that are over 100 A long are presented. They are based on oligo(thiophene-ethynylene)s and oligo(phenylene-ethynylene)s. A method for attachment of molecular-sized alligator clips is presented. These serve as bonding locations to gold probes.

Synthesis of well-defined conjugated oligomers for molecular electronics

Described are methods for the rapid syntheses of conjugated oligomers of precise length and constitution by an iterative divergentkonvergent approach. The syntheses can be carried out in solution or on a polymer support. The properties of the conjugated oligomers are presented as well there potential to act as molecular wires.

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 A long. The synthesis of a mixed phenylen...