The larger N-heteroacenes

The history and development of pyrazine- and pyridine-type heteroacenes and their use in solid-state organic electronics are discussed and reviewed. The larger N-heteroacenes are potential electron- or hole-transporting materials and should therefore complement acenes in organic electronics. As they feature electronegative nitrogen ring atoms in their molecular skeleton, issues with oxidation should be less problematic when comparing them to the larger acenes such as pentacene. This paper covers the synthesis and the solid-state packing of larger (tetracene/pentacene-based) N,N-heterocylic acenes as well as the question of the interplay of aromaticity and antiaromaticity in the known larger N-heteroacenes and their N,N-dihydro-derivatives; also illuminated are their optical properties. A literature overview is provided.