A Controlled, Iterative Synthesis and the Electronic Properties of Oligo[(p-phenyleneethynylene)-a lt-(2,5-siloleneethynylene)]s

An introductory series of conjugated siloleneethynylene co-oligomers has been prepared from a key 2-chloro-5-iodosilole intermediate via site-specific cross-coupling reactions. The tetramer (9) and pentamer (10) both exhibit absorption maxima matching those of the corresponding silole copolymers. Extinction coefficients for the oligomers in this series are large, and in the case of the pentamer (10) the value exceeds 180 000 M-1 cm-1. The compounds all emit in the visible region with the greatest quantum efficiencies being 8.97 × 10-2 (monomer) and 2.99 × 10-2 (pentamer).