Institut für Anorganische Chemie, Goethe-Universität Frankfurt, Max-von-Laue-Strasse 7, 60438, Frankfurt (Main), Germany.
Dipartimento di Chimica, Università degli Studi di Milano, Via Camillo Golgi 19, 20133, Milano, Italy.
Angew Chem Int Ed Engl. 2023 Jan 26;62(5):e202215468. doi: 10.1002/anie.202215468. Epub 2022 Dec 20.
Helicenes combine two central themes in chemistry: extended π-conjugation and chirality. Hetero-atom doping preserves both characteristics and allows modulation of the electronic structure of a helicene. Herein, we report the (BO) -doped tetrathia[7]helicene 1, which was prepared from 2-methoxy-3,3'-bithiophene in four steps. 1 is formally derived by substituting two (Mes)B-O moieties in place of (H)C=C(H) fragments in two benzene rings of the parent tetrathia[7]helicene. X-ray crystallography revealed a dihedral angle of 50.26(9)° between the two terminal thiophene rings. The (P)-/(M)-1 enantiomers were separated by chiral HPLC and are configurationally stable at room temperature. The experimentally determined enantiomerization barrier of 27.4±0.1 kcal mol is lower than that of tetrathia[7]helicene (39.4±0.1 kcal mol ). The circular dichroism spectra of (P)- and (M)-1 show a perfect mirror-image relationship. 1 is a blue emitter (λ =411 nm) with a photoluminescence quantum efficiency of Φ =6 % (cf. tetrathia[7]helicene: λ ≈405 nm, Φ =5 %).
扩展的π共轭和手性。杂原子掺杂既能保留这两个特性，又能调节螺苯并噻吩类化合物的电子结构。在此，我们报告了（BO）掺杂的四噻[7]螺苯并噻吩 1，它是由 2-甲氧基-3,3'-联噻吩经四步反应制备得到的。1 是通过用两个（Mes）B-O 取代母体四噻[7]螺苯并噻吩两个苯环中（HC=C（H））片段，从理论上推导而来的。X 射线晶体学表明，两个末端噻吩环之间的二面角为 50.26(9)°。（P）-/（M）-1 对映异构体通过手性 HPLC 分离，在室温下构型稳定。实验确定的对映体异构化势垒为 27.4±0.1 kcal mol，低于四噻[7]螺苯并噻吩（39.4±0.1 kcal mol）。（P）-和（M）-1 的圆二色光谱呈现出完美的镜像关系。1 是一个蓝色发光体（λ =411 nm），荧光量子效率为 Φ =6 %（相比之下，四噻[7]螺苯并噻吩：λ ≈405 nm，Φ =5 %）。
