Toyoda Masataka, Imai Yoshitane, Mori Tadashi
Department of Applied Chemistry, Graduate School of Engineering, Osaka University , 2-1 Yamada-oka, Suita, Osaka, 565-0871, Japan.
Department of Applied Chemistry, Faculty of Science and Engineering, Kindai University , 3-4-1 Kowakae, Higashi-Osaka, Osaka 577-8502, Japan.
J Phys Chem Lett. 2017 Jan 5;8(1):42-48. doi: 10.1021/acs.jpclett.6b02492. Epub 2016 Dec 12.
Chiral boron dipyrromethenes (BPs) enjoy high fluorescence efficiency at visible to near-IR wavelength regions with a reasonable range of dissymmetry factors. Here, we demonstrate that the (quasi)propeller chirality, similarly to hexagonal propeller in hexaarylbenzene, can be effectively induced in heptaarylated BP. In addition, supramolecular dimer was formed at low temperatures in nonpolar solvent, which exhibits strong bisignate Cotton effects at BP transitions (the couplet amplitude A = 193 M cm) in the circular dichroism (CD). Due to the bulky substituents on the propeller blades, but with void space around boron atoms, BP chromophores in the dimer are aligned in a head-to-tail manner with a small torsion (φ ≈ 15°), to avoid fluorescence quenching usually observed in H-type dimer of BPs, exhibiting strong circularly polarized luminescence (CPL) signals (g = 2.0 × 10, Φ = 0.45). Such supramolecular dimer formation would be viewed as an alternative approach for designing and developing novel chiroptical materials.
手性硼二吡咯亚甲基（BPs）在可见光到近红外波长区域具有较高的荧光效率，且不对称因子范围合理。在此，我们证明了（准）螺旋手性，类似于六芳基苯中的六方螺旋，可以在七芳基化的BP中有效诱导。此外，在非极性溶剂中低温下形成了超分子二聚体，其在圆二色性（CD）中的BP跃迁处表现出强烈的双符号科顿效应（偶合振幅A = 193 M cm）。由于螺旋桨叶片上的庞大取代基，但硼原子周围有空隙空间，二聚体中的BP发色团以头对尾的方式排列，扭转角较小（φ≈15°），以避免通常在BPs的H型二聚体中观察到的荧光猝灭，表现出强烈的圆偏振发光（CPL）信号（g = 2.0×10，Φ = 0.45）。这种超分子二聚体的形成将被视为设计和开发新型手性光学材料的一种替代方法。
