DOI: 10.1002/chem.201101198 Hexaazatriphenylene (HAT) versus tri-HAT: The Bigger the Better? Rafael Juµrez, [a, b] María Moreno Oliva, [c] Mar Ramos, [b] JosØ L. Segura,* [a] Carlos Alemµn, [d] Francisco Rodríguez-Ropero, [d] David Curcó, [e] Francisco Montilla, [f] Veaceslav Coropceanu, [g] Jean Luc BrØdas, [g] Yabing Qi, [h] Antoine Kahn, [h] M. Carmen Ruiz Delgado, [c, g] Juan Casado,* [c] and Juan T. López Navarrete* [c] Dedicated to the memory of our friend and teacher Professor Rafael Suau Introduction There is growing interest in organic semiconductors owing to their potential applications in electronic and optoelec- tronic devices. The majority of organic semiconductors in- vestigated to date display hole-transport properties. In many instances, however, such as light-emitting diodes and photo- voltaic cells, as well as for complementary circuit applica- tions, both electron- and hole-transport materials are re- quired. Although there is currently significant effort toward the development of electron-channel transporting materials, only a limited number of electron-transport materials have been reported in the literature, for example, fullerene deriv- atives, naphthalene/perylene diimides, perfluorinated com- pounds, and quinoidal oligothiophene compounds. [1] Recent- ly, 1,4,5,8,9,12-hexaazatriphenylene (HAT, Scheme 1) deriv- atives have been added to this group. In these materials, the pyrazine function induces the electron-deficient character, leading to electron-acceptor properties. [2] HAT itself was first synthesized in 1981 as a metal ligand for coordination chemistry. [3] Although most of the literature concerned with the HAT system deals with its coordination properties and the properties of the corresponding complexes, more atten- tion was recently devoted to the structure of HAT deriva- Abstract: A new hexaazatriphenylene (HAT) derivative formed by the fusion of three HAT units has been prepared and its electronic and molecular struc- tures have been fully characterized by optical and vibrational Raman spec- troscopy, electrochemistry, solid-state UV and inverse photoemission spec- troscopy (UPS and IPES), and by quantum-chemical calculations. A com- parative HAT versus tri-HAT study was performed. The fusion of three HAT molecules causes modifications in the optical and electrochemical proper- ties consistent with enhanced p-elec- tron delocalization attained in a bigger planar core. Such combined experi- mental and theoretical studies are useful to balance chemical design with supramolecular engineering directed to find enhanced characteristics for new organic semiconductor applications. Keywords: density functional theo- ry · hexaazatriphenylenes · Raman spectroscopy · supramolecular chemistry [a] Dr. R. Juµrez, Prof. Dr. J. L. Segura Department of Organic Chemistry Complutense University of Madrid, Faculty of Chemistry Madrid 28040 (Spain) [b] Dr. R. Juµrez, Prof. Dr. M. Ramos Department of Environmental and Technological Chemistry Universidad Rey Juan Carlos, Madrid, 28933 (Spain) [c] Dr. M. M. Oliva, Dr. M. C. Ruiz Delgado, Prof. Dr. J. Casado, Prof. Dr. J. T. López Navarrete Department of Physical Chemistry, University of Mµlaga Campus de Teatinos s/n, Mµlaga 29071 (Spain) Fax: (+ 34) 952132000 E-mail : segura@quim.ucm.es casado@uma.es teodomiro@uma.es [d] Prof. Dr. C. Alemµn, Dr. F. Rodríguez-Ropero Departament dEnginyeria Química E. T. S. dEnginyeria Industrial de Barcelona Universitat Politcnica de Catalunya, Diagonal 647 Barcelona 08028 (Spain) [e] Dr. D. Curcó Deparment dEnginyeria Química, Facultat de Química Universitat de Barcelona, Martí Franques 1 Barcelona 08028 (Spain) [f] Dr. F. Montilla Instituto Universitario de Materiales de Alicante Universidad de Alicante, Alicante 03080 (Spain) [g] Dr. V. Coropceanu, Prof. Dr. J. L. BrØdas, Dr. M. C. Ruiz Delgado School of Chemistry and Biochemistry Georgia Institute of Technology, Atlanta Georgia 30332-0400 (USA) [h] Dr. Y. Qi, Prof. Dr. A. Kahn Department of Electrical Engineering Princeton University, Princeton New Jersey 08544 (USA) Supporting information (additional spectroscopic, photophysical, and computational details) for this article is available on the WWW under http ://dx.doi.org/10.1002/chem.201101198.  2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Chem. Eur. J. 2011, 17, 10312 – 10322 10312