Hanida Kensuke, Kim Jinseok, Fukui Norihito, Tsutsui Yusuke, Seki Shu, Kim Dongho, Shinokubo Hiroshi
Department of Molecular and Macromolecular Chemistry, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8603, Japan.
Department of Chemistry and Spectroscopy Laboratory for, Functional π-Electronic Systems, Yonsei University, Seoul, 03722, South Korea.
Angew Chem Int Ed Engl. 2021 Sep 13;60(38):20765-20770. doi: 10.1002/anie.202109003. Epub 2021 Aug 24.
s-Indacene is a classical non-alternant hydrocarbon that contains 12 π-electrons in a cyclic π-conjugation system. Herein, we report its nitrogen-doped analogue, 1,5-diaza-s-indacene. 1,5-Diaza-s-indacenes were readily prepared from commercially available 2,5-dichlorobenzene-1,4-diamine through a two-step transformation consisting of a palladium-catalyzed Larock cyclization with diaryl acetylenes followed by hydrogen abstraction. The thus obtained 1,5-diaza-s-indacenes exhibited distinct antiaromaticity, as manifested in clear bond-length alternation, a forbidden HOMO-LUMO transition, and a paratropic ring current. As compared to the parent s-indacene, the 1,5-diaza-s-indacenes showed higher electron-accepting ability owing to the presence of imine-type nitrogen atoms. The 1,5-diaza-s-indacene core is effectively conjugated with the peripheral aryl groups, which enables fine-tuning of the absorption spectra and redox properties. The two possible localized forms of 1,5-diaza-s-indacene were compared in terms of their energetic aspects.
s-茚并芴是一种经典的非交替烃，在环状π共轭体系中含有12个π电子。在此，我们报道其氮掺杂类似物1,5-二氮杂-s-茚并芴。1,5-二氮杂-s-茚并芴可通过两步转化，由市售的2,5-二氯苯-1,4-二胺轻松制备，该两步转化包括钯催化的与二芳基乙炔的Larock环化反应，随后进行氢提取。如此获得的1,5-二氮杂-s-茚并芴表现出明显的反芳香性，表现为明显的键长交替、禁阻的HOMO-LUMO跃迁和顺磁环电流。与母体s-茚并芴相比，由于亚胺型氮原子的存在，1,5-二氮杂-s-茚并芴显示出更高的电子接受能力。1,5-二氮杂-s-茚并芴核心与外围芳基有效共轭，这使得吸收光谱和氧化还原性质能够得到微调。从能量方面比较了1,5-二氮杂-s-茚并芴的两种可能的局域形式。
