POTENTIAL MOLECULAR WIRES AND MOLECULAR ALLIGATOR CLIPS

The synthesis of oligo(2-ethylphenylene-ethynylene)s, oligo(2-(3'-ethy lheptyl)phenylene-ethynylene)s and oligo(3-ethylthiophene-ethynylene)s is described via an iterative divergent convergent approach. Synthesi zed were the monomer, dimer, tetramer, octamer and 16-mer of the oligo (3-ethylthiophene-ethynylene)s and oligo(2-3'-ethylheptyl)phenylene-et hynylene)s. The 16-mers are 100 Angstrom and 128 Angstrom long, respec tively. At each stage in the iteration, the length of the framework do ubles. Only three sets of reaction conditions are needed for the entir e iterative synthetic sequence; an iodination, a protodesilylation, an d a Pd/Cu-catalyzed cross coupling. The oligomers were characterized s pectroscopically and by mass spectrometry. The optical properties are presented which show the stage of optical absorbance saturation. The s ize exclusion chromatography values for the number average weights, re lative to polystyrene, illustrate the tremendous differences in the hy drodynamic volume of these rigid rod oligomers versus the random coils of polystyrene. These differences become guile apparent at the octame r stage. The preparation of thiol-protected end groups is described. T hese may serve as molecular alligator clips for adhesion to gold surfa ces. These oligomers may act as molecular wires in molecular electroni c devices and they also serve as useful models for understanding relat ed bulk polymers.