Large N‐Heteroacenes: New Tricks for Very Old Dogs?

Abstract

Azaacenes have been known for a very long time, either as N,N'-dihydro compounds or in their oxidized form as 4n+2π systems, but only recently have processable and charcterizable derivatives been sought. In the last three years synthetic routes to large N-heteroacenes have been developed. In particular, the Pd-catalyzed coupling of aromatic diamines with activated aromatic dihalogenides has enabled simple access to numerous new azaacenes. Since 2010, azapentacene and stabile oligoazahexacene have been synthesized, as well as a symmetrical tetraazapentacene, which acts as an excellent electron-transport material for thin-film transistors.

Trends in molecular design strategies for ambient stable n-channel organic field effect transistors

“…Hence, theoretical analysis predicts that N-atoms in the p-conjugated backbone switch the charge transport properties of oligoacenes from the p-channel to the n-channel. 257,258 Oligoazaacenes have permanent dipole moments that induce switching of packing motifs from herringbone to p-stacked with short intermolecular stacking distances. Excellent electron mobilities are predicted using the Marcus theory.…”

WITHDRAWN: Hydrogen-bonding versus π–π stacking in the design of organic semiconductors: From dyes to oligomers

“…The possibility of achieving n-type transport and promoting hydrogen-bondingability by the introduction of N atoms has initiated the intense investigation of oligoazaacenes, such as diaza-and tetraazapentacene [80]. Diazaand tetraazapentacene can exist both in the reduced and oxidised states [81]. The reduced A c c e p t e d M a n u s c r i p t 18 form of these oligoazaacenes is antiaromatic.…”

“…Consequently, according to Clar's rule, to achieve an equally large aromatic system on the two sides of the molecule it is necessary to position the reduced dihydropyrazine units close to the centre of the molecule. This restriction explains the much larger interest in the oxidised forms compared with the reduced forms [81].…”

Effect of the mismatch structure on crystal packing, physical properties and third-order nonlinearity of unsymmetrical twistacenes

“…To overcome these drawbacks, one of the methods is to incorporate the heteroatoms into the acene skeletons [11][12][13][14][15][16][17][18][19][20]. Another method is to introduce five-membered rings to replace the traditional six-membered rings [21][22][23].…”