Iterative Divergent/Convergent Doubling Approach to Linear Conjugated Oligomers. A Rapid Route to a 128 A Long Potential Molecular Wire
SOUTH CAROLINA UNIV COLUMBIA DEPT OF CHEMISTRY AND BIOCHEMISTRY
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Described is the synthesis of oligo2-ethylphenylene-ethynylenes and oligo2-3ethylheptylphenylene-ethynylenes via an iterative divergent convergent approach. Synthesized were the monomer, dimer, tetramer, and octamer of the ethyl derivative and the monomer, dimer, tetramer, octamer, and 16-mer of the ethylheptyl derivative. The 16-mer is 128 A long. 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 PdCu-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 verses the random coils of polystyrene. These differences become quite apparent at the octamer stage. These oligomers may act as molecular wires in molecular electronic devices and they also serve as useful models for understanding related bulk polymers.
- Polymer Chemistry
- Electricity and Magnetism