Liu Lu, Li Sheng, Zhang Nan, Shi Qiyuan, Liu Ke, Liu Taihong, Huang Zhiyan, Ding Liping, Fang Yu
Key Laboratory of Applied Surface and Colloid Chemistry of Ministry of Education, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi'an, Shaanxi 710119, People's Republic of China.
J Phys Chem B. 2023 Nov 30;127(47):10171-10178. doi: 10.1021/acs.jpcb.3c06757. Epub 2023 Nov 15.
Time-resolved evolution of excited states in the twist-conjugated chromophores is of great fundamental interest for photoluminescent applications. The four diaryl BODIPY triads modified with diverse end-cappers at 2,6-positions were investigated properly, and considerable two-photon absorption capabilities in the first biological spectral window were obtained. Fast relaxations from the initially twisted conformation to the planarized conformation in the excited state were resolved spectrally and kinetically, accompanied by the discernible phenomenon of the fluorescence dynamic Stokes shift (DSS). Along with increasing electron donating capabilities and solvent polarities, the characteristics of structural rearrangement and intramolecular charge transfer have been estimated by enhanced DSS behaviors. Especially, the blue-shifted DSS was rationalized as the sequence conversion between the planarized state and the twisted charge transfer state. A molecular-level picture for relaxation pathways in different polarities was depicted and supported by the theoretical simulations. Significant and fast structural motions in this work contribute to the excited-state dynamics and rational development of versatile BODIPY chromophores.
对于光致发光应用而言，扭曲共轭发色团中激发态的时间分辨演化具有重大的基础研究意义。对在2,6位用不同封端剂修饰的四个二芳基BODIPY三联体进行了恰当研究，并在第一个生物光谱窗口中获得了可观的双光子吸收能力。从激发态下最初的扭曲构象到平面化构象的快速弛豫在光谱和动力学上得到了解析，同时伴随着荧光动态斯托克斯位移（DSS）这一可辨别的现象。随着给电子能力和溶剂极性的增加，通过增强的DSS行为对结构重排和分子内电荷转移的特征进行了评估。特别地，蓝移的DSS被合理地解释为平面化状态和扭曲电荷转移状态之间的序列转换。描绘了不同极性下弛豫途径的分子水平图像，并得到了理论模拟的支持。这项工作中显著且快速的结构运动有助于激发态动力学以及通用BODIPY发色团的合理开发。
