Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry & Chemical Engineering, Shaanxi Normal University, Xi'an 710062, People's Republic of China.
J Phys Chem B. 2023 Mar 9;127(9):2044-2051. doi: 10.1021/acs.jpcb.3c00347. Epub 2023 Feb 27.
Three 2,6-electron donor-substituted boron dipyrromethene (BODIPY) exhibiting an intramolecular charge transfer (ICT) character with large Stokes shift and moderate fluorescence quantum yields were designed and synthesized. Broadband femtosecond transient absorption (fs-TA) spectroscopy measurements were performed to directly detect the CT state in nonpolar or less polar solvents and the charge separation (CS) state in more polar solvents. A solid foundation for the fs-TA assignment can be found in electrolysis experiments. In addition, the ICT character of the newly designed compounds was investigated by density functional theory (DFT) calculations. Meanwhile, the reference compounds without the donor groups were synthesized, and their photophysical behaviors and ultrafast time-resolved spectra confirmed that no ICT process occurred regardless of the nature of the solvent. This work emphasizes the importance of decorating the BODIPY core with electron-donating substituents at 2,6-positions to efficiently adjust its photofunctional behaviors demonstrating the ICT character. Importantly, the photophysical processes could be easily regulated by changing the solvent with different polarities.
三种具有 2,6-二电子给体取代基的硼二吡咯亚甲基（BODIPY）被设计和合成，它们具有大斯托克斯位移和中等荧光量子产率的分子内电荷转移（ICT）特性。宽带飞秒瞬态吸收（fs-TA）光谱测量用于直接在非极性或低极性溶剂中检测 CT 态，在更极性溶剂中检测电荷分离（CS）态。在电解实验中可以找到 fs-TA 分配的坚实基础。此外，通过密度泛函理论（DFT）计算研究了新设计化合物的 ICT 特性。同时，合成了没有供体基团的参比化合物，它们的光物理行为和超快时间分辨光谱证实，无论溶剂的性质如何，都不会发生 ICT 过程。这项工作强调了在 2,6 位用给电子取代基修饰 BODIPY 核以有效调节其光功能行为的重要性，证明了 ICT 特性。重要的是，通过改变具有不同极性的溶剂，可以很容易地调节光物理过程。
