Large N-Heteroacenes

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We propose synthesis and property evaluation of large N-heteroacenes. Several aspects will be illuminated. 1) Synthesis of symmetrical tetraazapentacenes featuring chloro and cyano substituents as materials for electron transport in thin film transistors. 2) Extension of structural diversity, synthesis of azaheptacenes and azaoctacenes and developing strategies that suppress both reduction as well as butterfly dimerization always observed in the larger azaacenes. With this strategy we will attempt to prepare an azanonacene, but it is not clear if we do hit the limit of stabilization, even if we employ a combination of steric and electronic protection. 3) We will prepare triangular azaacenes as larger representatives of hexaazacyclotrinaphthylene (HATNA) types. 4) We will build up large azaacenes with embedded cyclobutadiene rings. Our modular approach allows the combination of building blocks into ever new molecular topologies employing commercially available or easily synthesized reagents. Basis structures are our diethynylated diaminobenzenes -naphthalenes and -anthracenes that undergo Pd-catalyzed coupling or classic condensation reactions with suitable dihalides, ortho-quinones or aromatic ortho-dihydroxy-compounds. The second part of the project investigates the materials properties of the thus produced azaacenes. We will relate molecular structure, morphology and device performance of the azaacenes in a semi-systematic way. This is possible as we have built up a simple device fabrication and characterization facility in Heidelberg. The azaacenes, close heterocyclic relatives of pentacene, lend themselves towards this approach.