Toward Full Zigzag-Edged Nanographenes: peri-Tetracene and Its Corresponding Circumanthracene

Abstract

Zigzag-edged nanographene with two rows of fused linear acenes, called as n- peri-acene (n-PA), is considered as a potential building unit in the arena of organic electronics. n-PAs with four ( peri-tetracene, 4-PA), five ( peri-pentacene, 5-PA) or more benzene rings in a row have been predicted to show open-shell character, which would be attractive for the development of unprecedented molecular spintronics. However, solution-based synthesis of open-shell n-PA has thus far not been successful because of the poor chemical stability. Herein we demonstrated the synthesis and characterization of the hitherto unknown 4-PA by a rational strategy in which steric protection of the zigzag edges playing a pivotal role. The obtained 4-PA possesses a singlet biradical character ( y = 72%) and exhibits remarkable persistent stability with a half-life time ( t) of ∼3 h under ambient conditions. UV-vis-NIR and electrochemical measurements reveal a narrow optical/electrochemical energy gap (1.11 eV) for 4-PA. Moreover, the bay regions of 4-PA enable the efficient 2-fold Diels-Alder reaction, yielding a novel full zigzag-edged circumanthracene.

A Peri‐tetracene Diradicaloid: Synthesis and Properties

“…In summary, a stable peri‐tetracene derivative PT‐2ClPh was obtained by using a new synthetic strategy . It was reasonably stable owing to the proper blocking of the most reactive sites at the two zigzag edges by the bulky and electron‐withdrawing 2,6‐dichlorophenyl groups.…”

Polycyclic aromatic hydrocarbons in the graphene era

“…Both compounds are closedshell structures that have been known for decades [188][189][190][191], whereas the higher homologues peri-tetracene 126 and peripentacene 127 start to exhibit open-shell diradical ground states (Figure 25(a)), thereby posing challenges for syntheses and characterizations. After a long pursuit of these structures, Liu and Feng et al [192] (Figure 25(b)) and Wu et al [193] independently synthesized different peri-tetracene derivatives 134 in 2018. Although the synthesis of peri-pentacene 127 has not been successful in solution, it has been demonstrated by Crommie and Fischer et al [194] through on-surface cyclodehydrogenation of 6,6′-bipentacene 135 under UHV ( Figure 25(c, d)).…”

Tailoring Bond Topologies in Open-Shell Graphene Nanostructures

“…Though the solution synthesis of a peri-tetracene derivative (n = 4) was recently realized, wherein its structural and electronic characterization in solution was hindered due to high reactivity of the compound, pristine peri-tetracene re-mains experimentally inaccessible. 27 Furthermore, onsurface synthesis of peri-pentacene (n = 5) was recently demonstrated on Au(111). 28 However, detailed experimental characterization of higher peri-acenes (n > 3), in particular their electronic structure, has not been report-ed previously and peri-acenes thus remain a virtually unexplored family of PAHs.…”