Synthesis and Functions of Azulene-Based Chiral Helicene Compounds

2020 Fiscal Year Final Research Report

• Project/Area Number: 18K05087
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 33010:Structural organic chemistry and physical organic chemistry-related
• Research Institution: Kyushu University
• Principal Investigator: Tani Fumito 九州大学, 先導物質化学研究所, 准教授 (80281195)
• Project Period (FY): 2018-04-01 – 2021-03-31
• Keywords: アズレン / ヘリセン / 不斉 / 酸化 / ラジカル / 電子スピン / チオフェン / パイ電子

Outline of Final Research Achievements

Chiral helicene compounds that have helical pi-conjugated frameworks comprised of ortho-fused aromatic rings have been intensively investigated. On the other hand, there have been very few studies accomplishing thorough characterization of helicene radicals, although they are of profound interest from the standpoint of fundamental sciences and technological fields. Helicene radicals are unique chemical species in that they have a combination of chirality and unpaired electron spin(s) delocalized on helical pi-conjugated orbital(s). In order to obtain a stable helicene radical, a new helicene compound named AIBTh was synthesized. Electron-donating isobenzothiophene and 1,1’-biazulene units are fused to afford the helical structure of AIBTh, which is the first azulene-based chiral helicene. Upon one-electron oxidation of AIBTh, its air-stable cation radical was successfully isolated. The X-ray crystal structure and specific electronic structure of this cation radical were clarified.

Free Research Field

物理有機化学，構造有機化学

Academic Significance and Societal Importance of the Research Achievements

単一の分子内にキラリティと電子スピンの両方を有するヘリセンのラジカル種は基礎科学および工学的応用の両面から重要でありながら，不安定であるために，その実例は極めて限られていた。本研究では，この課題の解決に取り組み，アズレン骨格を採用した新しい化合物を合成し，安定なラジカル種を得ることにも成功した。ヘリセン化合物の安定ラジカル種を得るための有用な知見を明らかにした点に学術的な意義がある。