Planarized Star-Shaped Oligothiophenes with Enhanced π-Electron Delocalization Yohann Nicolas, Philippe Blanchard,* Eric Levillain, Magali Allain, † Nicolas Mercier, † and Jean Roncali* Groupe Syste ` mes Conjugue ´ s Line ´ aires, IMMO, UMR CNRS 6501, UniVersite ´ d’Angers, 2 Bd LaVoisier, F-49045 Angers, France, and IMMO, UMR CNRS 6501, UniVersite ´ d’Angers, 2 Bd LaVoisier, F-49045 Angers, France philippe.blanchard@uniV-angers.fr; jean.roncali@uniV-angers.fr Received November 21, 2003 ABSTRACT Planarized star-shaped oligothiophenes 1 have been synthesized by connecting short-chain oligothiophenes on a benzo[1,2-b:3,4-b′:5,6-b′′]- trithiophene central core. Their electrochemical and optical properties have been characterized by cyclic voltammetry and UV-visible spectroscopy, respectively. These results associated with theoretical calculations show the advantage of benzotrithiophene as a central core in terms of π-electron delocalization. Thiophene-based π-conjugated oligomers 1 are the subject of considerable current interest due to their use as organic semiconductors for the realization of devices such as field- effect transistors, 2 light-emitting diodes, 3 and photovoltaic cells. 4 Despite the huge amount of work already invested in these various applications, it is clear that further progress in these fields implies an intensification of the research effort focused on the design and synthesis of new compounds with electrochemical, optical, and electronic properties specifically tailored for each type of application. In this context, we report here the synthesis and prelimi- nary characterizations of the first members of a new series of star-shaped oligothiophenes in which three short linear oligothiophene chains are connected to a central rigid trithienobenzene core. Star-shaped oligothiophenes with three or more oligoth- iophene chains attached to a central benzenic core have already been reported by several groups. 5 However, as shown by molecular models and confirmed by experimental data, ² IMMO. (1) Ba ¨uerle, P. In Electronic Materials: The Oligomer Approach; Mu ¨llen, K., Wegner, G., Eds.; Wiley-VCH: Weinheim, 1998; Chapter 2, pp 105- 197. (2) (a) Dimitrakopoulos, C. D.; Malenfant, P. AdV. Mater. 2002, 14, 99- 117. (b) Katz, H. E.; Lovinger, A. J.; Laquindanum, J. G. Chem. Mater. 1998, 10, 457-459. (c) Garnier, F.; Yassar, A.; Hajlaoui, R.; Horowitz, G.; Deloffre, F.; Servet, B.; Ries, S.; Alnot, P. J. Am. Chem. Soc. 1993, 115, 8716-8721. (d) Garnier, F.; Hajlaoui, R.; El Kassmi, A.; Horowitz, Laigre, L.; Porzio, W.; Armanini, M.; Provasoli, F. Chem. Mater. 1998, 10, 3334-3339. (3) (a) Mitschke, U.; Ba ¨uerle, P. J. Mater. Chem. 2000, 10, 1471-1507. (4) (a) Videlot, C.; El Kassmi, A.; Fichou, D. Solar Energy Mater. Solar Cells 2000, 63, 69. (b) Fichou, D. J. Mater. Chem. 2000, 10, 571-588. (c) Noma, N.; Tsuzuki, T.; Shirota, Y. AdV. Mater. 1995, 7, 647-648. (5) (a) Che ´rioux, F.; Guyard, L.; Audebert, P. Chem. Commun. 1998, 2225-2226. (b) Kotha, S.; Chakraborty, K.; Brahmachary, E. Synlett 1999, 10, 1621-1623. (c) Bras, J.; Guillerez, S.; Pe ´pin-Donat, B. Chem. Mater. 2000, 12, 2372-2384. (d) Che ´rioux, F.; Guyard, L. AdV. Funct. Mater. 2001, 11, 305-309. (e) Geng, Y.; Fechtenko ¨tter, A.; Mu ¨llen, K. J. Mater. Chem. 2001, 11, 1634-1641. (f) Pappenfus, T. M.; Mann, K. R. Org. Lett. 2002, 4, 3043-3046. (g) Ponomarenko, S. A.; Kirchmeyer, S.; Elschner, A.; Huisman, B.-H.; Karbach, A.; Drechsler, D. AdV. Funct. Mater. 2003, 13, 591-596. (h) Inoue, S.; Nischiguchi, S.; Murakami, S.; Aso, Y.; Otsubo, T.; Vill, V.; Mori, A.; Ujiie, S. J. Chem. Res., Synop. 1999, 596-597. ORGANIC LETTERS 2004 Vol. 6, No. 2 273-276 10.1021/ol0362764 CCC: $27.50 © 2004 American Chemical Society Published on Web 12/19/2003