Department of Applied Chemistry, Graduate School of Engineering, Nagoya University, Aichi, 464-8603, Japan.
Chem Asian J. 2013 Jan;8(1):178-90. doi: 10.1002/asia.201200723. Epub 2012 Oct 24.
We have demonstrated that the iridium-catalyzed direct borylation of hexa-peri-hexabenzocoronene (HBC) enables regioselective introduction of boryl groups to the para-, ortho-, and meta-substituted HBCs in high yields. The boryl groups have been transformed into various functionalities such as hydroxy, cyano, ethynyl, and amino groups. We have elucidated that the substituents significantly influence the photophysical properties of HBCs to enhance fluorescence quantum yields. DFT calculations revealed that the origin of the substituent effect is the lift in degeneracy in the frontier orbitals by an interaction with electron-donating and electron-withdrawing substituents at the para- and ortho-positions. The change in molecular orbitals results in an increase of the transition probability from the S(0)→S(1) states. In addition, the two-photon absorption cross-section values of para-substituted HBCs are significantly larger than those of ortho- and meta-substituted HBCs.
我们已经证明，铱催化的六并苯（HBC）的直接硼化反应能够以高产率实现硼基对 HBC 的对位、邻位和间位取代基的区域选择性引入。硼基已被转化为各种官能团，如羟基、氰基、乙炔基和氨基。我们已经阐明，取代基显著影响 HBC 的光物理性质，以提高荧光量子产率。DFT 计算表明，取代基效应的起源是通过与对位和邻位的供电子和吸电子取代基相互作用，使前线轨道的简并性升高。分子轨道的变化导致从 S(0)→S(1)态的跃迁概率增加。此外，对位取代的 HBC 的双光子吸收截面值明显大于邻位和间位取代的 HBC。
