|In order to combine the stability of α-oligothiophenes with the rigidity of pentacene, fully fused α-oligothiophenes, oligothienoacenes, were synthesized and their properties compared to the non-fused oligothiophenes. New synthetic methodology, utilizing removable solubilizing groups, was designed to efficiently prepare oligothienoacenes with up to seven fused rings (Scheme 1). The key steps involved the so called “halogen dance” reaction and Pd-catalyzed coupling of Bu3SnSSnBu3 to introduce sulfur linkages (Scheme 1). X-ray diffraction data indicate that pentathienoacene and heptathienoacene adopt π-stacked packing motifs. The optical data indicate that the longest absorption maximum of fused ring compounds is similar to the corresponding non-fused α-oligothiophenes. The emission spectra of pentathienoacene and heptathienoacene are significantly blue-shifted when compared to those of α-terthiophene and α-quaterthiophene, respectively, resulting in smaller Stokes Shifts.|
Scheme 1. Synthesis of heptathienoacene.
New Reactions and Methodology, Materials, Total Synthesis, Process R&D
8:00 PM-10:00 PM, Sunday, 28 August 2005 Washington DC Convention Center -- Hall A, Poster