Stable, Crystalline Acenedithiophenes with up to Seven Linearly Fused Rings Marcia M. Payne, Susan A. Odom, Sean R. Parkin, and John E. Anthony* Department of Chemistry, UniVersity of Kentucky, Lexington, Kentucky 40506-0055 anthony@uky.edu Received July 8, 2004 ABSTRACT We report the synthesis of a series of crystalline acenedithiophenes with up to seven linearly fused rings and silylethynyl substituents. These functional groups are designed to both improve solubility and enhance cofacial interactions in the solid. We discuss the crystal packing of these materials, as well as their physical properties such as oxidation potential, UV-vis absorption, fluorescence emission, and decomposition pathways. Polycyclic aromatic hydrocarbons represent a vast library of molecular geometries with properties exploitable for ma- terials chemistry. 1 The linearly fused acenes in particular have applications in field-effect transistors (FETs) 2 and organic light-emitting diodes (OLEDs). 3 Our research has emphasized the functionalization of acenes to improve solid-state ordering and increase solubility and stability. For example, 6,13-bis- (triisopropylsilylethynyl) pentacene (TIPS pentacene) packs in a 2-dimensional π-stacked array in the solid state, yielding improved conductivity, reduced band gap, 4 and FET devices with a hole mobility of 0.4 cm 2 /Vs. 5 Spurred by these promising results, we wished to apply our functionalization approach to other fused systems, to further our structure- property relationship studies of organic semiconductors. One of the most promising systems for such study involves a fusion of acenes and oligothiophenes: 6 alkylated anthra- dithiophene systems were recently reported by Katz and co- workers as part of their search for new materials for use in organic FETs. Their materials, 7 synthesized as an inseparable mixture of syn- and anti-isomers, exhibited hole mobilities as high as 0.15 cm 2 /Vs with good device stability. A recent theoretical treatment of these materials showed them to have great promise if the proper molecular packing could be attained, particularly orderings that enhanced π-face interac- tions. 8 To us, substitution of thiophene for the “terminal” benzene rings of an acene is attractive because it should not significantly perturb the basic molecular geometry compared to the acene hydrocarbons. Increased stability in these pentacene-like derivatives also indicates that this might be (1) Clar, E. Polycyclic Hydrocarbons; Academic Press: New, York, 1964; Vols. I and II. (2) (a) Butko, V. Y.; Chi, X.; Lang, D. V.; Ramirez, A. P. Appl. Phys. Lett. 2003, 83, 4773. (b) Zhang, Y.; Petta, J. R.; Ambily, S.; Shen, Y.; Ralph, D. C.; Malliaras, G. C. AdV. Mater. 2003, 15, 1632. (c) Dimitra- kopoulos, C. D.; Kymissis, I.; Purushothaman, S.; Neumayer, D. A.; Duncombe, P. R.; Laibowitz, R. B. AdV. Mater. 1999, 11, 1372. (d) Lin, Y. Y.; Gundlach, D. J.; Nelson, S.; Jackson, T. N. IEEE Trans. Electron DeVices 1997, 44, 1325. (3) (a) Wolak, M. A.; Jang, B.-B.; Palilis, L. C.; Kafafi, Z. H. J. Phys. Chem. B 2004, 108, 5492. (b) Odom, S. A.; Parkin, S. R.; Anthony, J. E. Org. Lett. 2003, 5, 4245. (4) (a) Anthony, J. E.; Eaton, D. L.; Parkin, S. R. Org. Lett. 2002, 4, 15. (b) Anthony, J. E.; Brooks, J. S.; Eaton, D. L.; Parkin, S. R. J. Am. Chem. Soc. 2001, 123, 9482. (5) Sheraw, C. D.; Jackson, T. N.; Eaton, D. L.; Anthony, J. E. AdV. Mater. 2003, 15, 2009. (6) Fichou, D.; Horowitz, G.; Bai, X.; Garnier, F. Synth. Met. 1992, 48, 167. (7) Laquindanum, J. G.; Katz, H. E.; Lovinger, A. J. J. Am. Chem. Soc. 1998, 120, 664. (8) Kwon, O.; Coropceanu, V.; Gruhn, N. E.; Durivage, J. C.; Laquin- danum, J. G.; Katz, H. E.; Cornil, J.; Bre ´das, J. L. J. Chem. Phys. 2004, 120, 8186. ORGANIC LETTERS 2004 Vol. 6, No. 19 3325-3328 10.1021/ol048686d CCC: $27.50 © 2004 American Chemical Society Published on Web 08/24/2004