Iterative Synthesis and Characterization of Cross-Conjugated Iso-Polydiacetylenes ZhaoYuming CampbellKatie TykwinskiRik R. 2001 An iterative synthesis of cross-conjugated iso-polydiacetylenes (iso-PDAs) is reported based on three fundamental building blocks:  vinyl triflates <b>8</b>, <b>9</b>, and <b>25</b>. An efficient sequence of palladium-catalyzed cross-coupling reactions of vinyl triflates and terminal alkynes has been employed to extend the chain length of these oligomers. The longest member of the series, nonamer <b>19</b>, spans 3.4 nm from Si to Si atom. The stability and solubility of the conjugated oligomers have been evaluated as a function of pendant substitution. Assessment of solid-state structural properties was achieved via X-ray crystallographic analyses of monomer <b>12</b> and trimer <b>14</b>. The electronic characteristics of the monodisperse oligomers have been fully analyzed by UV−vis spectroscopy in solution and as thin films, and these studies suggest that π-electron communication is present along the enyne framework, but quickly reaches saturation by the stage of nonamer <b>19</b>.