A Nitrogen‐Doped Hexapole [7]Helicene versus Its All‐Carbon Analogue

Abstract

Two synthetic nanographenes (NGs), N‐H7H and C‐H7H, were prepared. N‐H7H is doped with nitrogen, and C‐H7H is the all‐carbon analogue. Both are hexapole [7]helicenes (H7Hs), and their structures were identified by single‐crystal X‐ray diffraction. Sharp contrasts in absorption (absλmax, 683 vs. 593 nm), emission (emλmax, 894 vs. 777 nm), and electrochemical behavior (oxE1, 0.28 vs. 0.53 V) were observed between N‐H7H and C‐H7H, and the origin of these differences was rationalized by theoretical calculations. Studies on N‐H7H and C‐H7H set a clear example to elucidate the remarkable effects of N‐doping on the physical properties of NGs.

Multiple [n]helicenes with various aromatic cores

“…19). For example, diindeno[1,2,3,4defg;1′,2′,3′,4′-mnop]chrysene 52 is a buckybowl with a small bowl-to-bowl inversion barrier and excellent solubility in common organic solvents and is a candidate core for constructing quadruple [7]helicene (48) or other quadruple [n]helicenes. Hydrazinobuckybowl 53 is an analogue of diindeno [1,2,3,4-defg;1′,2′,3′,4′-mnop]chrysene, which exhibits red fluorescence and diverse topologies in neutral conditions.…”

“…Doping helicene skeletons with nitrogen atoms is an effective way to tune the electronic structure of helicenes. To understand the exact effecct of nitrogen doping on hexapole [7]helicene, Wang et al 48 synthesized a nitrogen-doped hexapole [7]helicene (35) with a HBC unit as the core and its allcarbon analogue (36) by cobalt-catalyzed [2 + 2 + 2] cyclotrimerization and dehydrocyclization reactions (Fig. 12).…”