Azepine‐ or Oxepine‐embedded Double Saddle‐Helix Nanographenes. Issue 2 (27th December 2021)

• Record Type: Journal Article
• Authors: Li, Ranran; Ma, Bin; He, Run‐Ying; Zhang, Bin; Zhang, Yi‐Kang; Feng, Shi‐Yu; An, Peng
• Is Part Of: Chemistry, an Asian journal. Volume 17:Issue 2(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-12-27
• Subjects: polycyclic aromatic hydrocarbon -- nanographene -- heteroatom-doped structure -- saddle-helix -- aromaticity; Chemistry -- Periodicals; 540.5
• DOI: 10.1002/asia.202101365
• Languages: English
• ISSNs: 1861-4728

Abstract

Abstract: The azepine‐ and oxepine‐embedded polycyclic aromatic hydrocarbons (PAH) 1 –3, as the hexa‐ peri ‐hexabenzocoronene (HBC)‐based nanographenes (NG) were designed and synthesized by Diels‐Alder reaction of cyclic alkene with tetrachlorothiophene‐S, S‐dioxide, followed by Suzuki‐Miyaura cross‐coupling and Scholl‐type cyclodehydrogenation. Due to the strained seven‐membered ring and the inherent structural pattern, heteroatom‐doped NGs 1 –3 show C s symmetrical, double saddle‐helix hybrid conformation, which represents a new shape for HBC based nanographenes. The calculation studies reveal the low aromaticity of the 8π heterocycles themselves and the heterocycles also decrease the electron delocalization of benzenes surrounding them. Dynamics‐based calculation suggests the C s symmetry would maintain druing the saddle‐inversion process. Meanwhile, we show property perturbation by doping with different heteroatoms. Abstract : The azepine‐ and oxepine‐embedded nanographenes were synthesized. By introducing the hetero‐heptagon ring, the new structures exhibit a double saddle‐helix shape as the meso ‐structure. The heterocyclic rings display less aromaticity and can decrease the electron delocalization around it. Meanwhile, heteroatom‐dependent fluorescent properties were observed.