A novel rational synthetic pathway—the “functionalization of para-nitroaniline” (FpNA)—provides substituted hexaarylbenzenes (HABs) with uncommon symmetries that bear up to five different substituents, fully avoiding regioisomeric product distributions during the reactions. 4-Nitroaniline is functionalized by a cascade of electrophilic halogenations, Sandmeyer brominations, and Suzuki cross-coupling reactions, leading to 26 substitution geometries, of which 18 structures are not available by the current established techniques. Furthermore, we demonstrate that this method is applicable to the bulk production of such systems on a multigram scale. Regarding optoelectronic properties, we demonstrate how highly functionalized HABs can show strong luminescent behavior, making these molecules very attractive to organic electronic devices.

Erstmals ist es gelungen, einen rationalen Syntheseplan – die “Funktionalisierung von para-Nitroanilin” (FpNA) – zur Herstellung substituierter Hexaarylbenzole (HABs) mit ungewöhnlichen Symmetrien und mit bis zu fünf verschiedenen Substituenten zu realisieren. Dabei konnte jegliches Auftreten regioisomerer Produktverteilungen während der Reaktion ausgeschlossen werden. 4-Nitroanilin wird dabei in einer Kaskade von elektrophilen Halogenierungen, Sandmeyer-Bromierungen und Suzuki-Kupplungen funktionalisiert. Dies führt zu 26 Substitutionsgeometrien, von denen 18 nicht mit den gewöhnlichen Methoden zu erhalten sind. Des Weiteren demonstrieren wir, dass dieses Verfahren geeignet ist, solche Systeme im Multigramm-Maßstab herzustellen. Hinsichtlich der optoelektronischen Eigenschaften zeigen wir, dass hochfunktionalisierte HABs starkes Lumineszenzverhalten aufweisen, was diese Moleküle besonders für Anwendungen in der organischen Elektronik interessant macht.

Fused porphycenes have attracted growing interest in recent years. However, the molecules generated to date suffer from different drawbacks such as multistep syntheses, low yields, and the lack of a convenient synthetic strategy. Here, we present our latest results concerning the synthesis of a suitable platform for the generation of large fused porphycenes.

A free-base porphyrin carrying two hexabenzocoronene (HBC) substituents in a trans arrangement and its zinc complex have been prepared. The compounds were characterized extensively and found to form tricationic dimers in the gas phase. X-ray crystallography confirms for the zinc complex a profound π-stacking of the HBC moieties. In contrast, the free-base porphyrin incarcerates n-heptane which essentially prevents π-stacking. Upon excitation of the HBC substituents, efficient energy transfer to the central porphyrin is observed.