2,9-Dibromopentacene: Synthesis and the role of substituent and symmetry on solid-state order

We have developed an effective synthetic route for 2,9-dibromopentacene, opening up new possibilities for future derivatization of pentacene. We also present the fundamental properties. Thin-film and single-crystal field-effect transistor results demonstrate a decrease in apparent charge transport efficiency with decreasing symmetry. The trend in symmetry was further correlated to single-crystal structural analysis, which implied that reduction in symmetry also reduced solid-state order. It is likely that this reduction in order is responsible for the diminished performance in the solid-state films and crystal, despite a reduction in overall tilt angle of the molecules relative to one another. Combined with previous studies, this work provides a more complete perspective on the interplay of symmetry, energetic, and intermolecular interactions in the macroscopic properties of solid-state organic electronic materials. (C) 2010 Elsevier B.V. All rights reserved.