Sakamaki Takumi, Zhang Yan, Fukuma Shota, Cruz Carlos M, Valdivia Abel Cárdenas, Campaña Araceli G, Casado Juan, Shang Rui, Nakamura Eiichi
Department of Chemistry, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan.
Departamento de Química Orgánica, Facultad de Ciencias, Unidad de Excelencia de Química Aplicada a Biomedicina y Medioambiente (UEQ), Universidad de Granada (UGR), Avenida Fuente Nueva s/n, 18071 Granada, Spain.
J Am Chem Soc. 2024 May 8;146(18):12712-12722. doi: 10.1021/jacs.4c02404. Epub 2024 Apr 24.
Persistent chiral organic open-shell systems have captured growing interest due to their potential applications in organic spintronic and optoelectronic devices. Nevertheless, the integration of configurationally stable chirality into an organic open-shell system continues to pose challenges in molecular design. The π-extended skeleton incorporated in spiro-conjugated carbocycles can provide robust chiroptical properties and a significant stabilization of the excited and ionic radical states. However, this approach has been relatively less explored in the design of persistent organic open-shell systems. We report here the ()-, ()-, and isomers of doubly spiro-conjugated carbocycles featuring flat and rigid carbon-bridged -phenylenevinylene () of different conjugation lengths connected by two spiro-carbon centers, which we denote for its quasi-dimeric structure. Our synthetic method based on a double lithiation cyclization approach enables facile production of . exhibit circularly polarized luminescence (CPL) with high fluorescence quantum yields (Φ) resulting in a high CPL brightness of 21 M cm and also exhibit high thermal and photostability. The monoradical cation of absorbing near-infrared light is notably persistent, exhibiting a half-life of 570 h under ambient conditions due to doubly spiro-conjugative stabilization. Theoretical and electrochemical studies indicate the radical cation of presents a non-Aufbau electron filling, exhibiting inversion of the energy level of the singly occupied molecular orbital (SOMO) and the highest (doubly) occupied molecular orbitals with the SOMO level even below the HOMO-1 level (double SHI effect). Our discoveries provide valuable insights into non-Aufbau molecules and the development of configurationally stable, optically active persistent radicals.
持久手性有机开壳体系因其在有机自旋电子器件和光电器件中的潜在应用而受到越来越多的关注。然而，将构型稳定的手性整合到有机开壳体系中在分子设计方面仍然面临挑战。并入螺共轭碳环的π-扩展骨架可以提供强大的手性光学性质以及激发态和离子自由基态的显著稳定。然而，这种方法在持久有机开壳体系的设计中相对较少被探索。我们在此报道了双螺共轭碳环的（）-、（）-和异构体，其具有由两个螺碳中心连接的不同共轭长度的扁平且刚性的碳桥连-亚苯基亚乙烯基（），因其准二聚体结构我们将其表示为。我们基于双锂化环化方法的合成方法能够轻松制备。表现出具有高荧光量子产率（Φ）的圆偏振发光（CPL），导致高CPL亮度为21 M cm，并且还表现出高热稳定性和光稳定性。吸收近红外光的的单自由基阳离子特别持久，由于双螺共轭稳定作用，在环境条件下表现出570 h的半衰期。理论和电化学研究表明的自由基阳离子呈现非奥弗贝格电子填充，单占据分子轨道（SOMO）和最高（双）占据分子轨道的能级发生反转，SOMO能级甚至低于HOMO - 1能级（双SHI效应）。我们的发现为非奥弗贝格分子以及构型稳定、光学活性持久自由基的发展提供了有价值的见解。
