title: Synthesis of a Tetrabenzotetraaza[8]circulene by a "Fold-In" Oxidative Fusion Reaction.
abstract: Tetrabenzotetraaza[8]circulene (1) has been synthesized in good yield by a "fold-in" oxidative fusion reaction of a 1,2-phenylene-bridged cyclic tetrapyrrole. X-ray diffraction analysis of 1 has revealed a planar square structure with a central cyclooctatetraene (COT) core that shows little alternation of the bond lengths. Despite these structural features, 1 shows aromatic-like character, such as sharp absorption bands, high fluorescence quantum yields (Φ(F)=0.55 in THF), and a single exponential fluorescence decay with τ(F)=3.8 ns. These observations indicate a dominant contribution of an [8]radialene-like π conjugation and hence aromatic character of the local aromatic segments in 1.
authors.affiliation: Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502 (Japan).
authors.forename: Fengkun
authors.initials: F
authors.lastname: Chen
authors.affiliation: Spectroscopy Laboratory for Functional π-Electronic Systems and Department of Chemistry, Yonsei University, Seoul 120-749 (Korea).
authors.forename: Yong Seok
authors.initials: YS
authors.lastname: Hong
authors.affiliation: Department of Applied Chemistry, Graduate School of Engineering, Kyushu University, Fukuoka 819-0395 (Japan).
authors.forename: Soji
authors.initials: S
authors.lastname: Shimizu
authors.affiliation: Spectroscopy Laboratory for Functional π-Electronic Systems and Department of Chemistry, Yonsei University, Seoul 120-749 (Korea). dongho@yonsei.ac.kr.
authors.forename: Dongho
authors.initials: D
authors.lastname: Kim
authors.affiliation: Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502 (Japan). taka@kuchem.kyoto-u.ac.jp.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Tanaka
authors.affiliation: Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502 (Japan). osuka@kuchem.kyoto-u.ac.jp.
authors.forename: Atsuhiro
authors.initials: A
authors.lastname: Osuka
keywords: aromaticity; circulenes; cyclooctatetraene; fused-ring systems; pyrroles