Web Release Date: July 7,
Synthesis and Structure of Fused 
-Oligothiophenes with up to Seven Rings
Department of Chemistry and the Macromolecular Science and Engineering Program, University of Michigan, 930 North University, Ann Arbor, Michigan 48109-1055
Received May 21, 2005
Abstract:
To combine the stability of -oligothiophenes with the planarity of acenes, fully fused oligothienoacenes were synthesized and their properties compared to the nonfused -oligothiophenes. By employing removable solubilizing groups, our synthetic methodology made it possible to efficiently prepare and purify oligothienoacenes with up to seven fused rings. The key steps involved the halogen dance reaction and Pd-catalyzed coupling of Bu3SnSSnBu3 to introduce sulfur linkages. This approach eliminates -
anion equilibration, a significant improvement over the traditional method of introducing sulfur linkages via Li-Br exchange. X-ray diffraction data indicate that pentathienoacene and heptathienoacene adopt 
-stacked packing motifs in contrast to the herringbone packing of nonfused oligothiophenes. On the basis of the linear dependence of the longest 
max on the reciprocal number of double bonds of thienoacenes with three to seven rings, the band gap of polythienoacene is extrapolated to be 2.21 eV.
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