文献类型：期刊文献

英文题名：Sequential Multistep Excited-State Structural Transformations in N,N′-Diphenyl-dihydrodibenzo[a,c]phenazine Fluorophores

作者：Jin, Xin[1,2];Guo, Shiyan[1,2];Wang, Xueli[3];Cong, Muyu[1,2];Chen, Jinquan[3];Zhang, Zhiyun[1,2];Su, Jianhua[1,2];Qu, Da-Hui[1,2];Tian, He[1,2]

机构：[1]East China Univ Sci & Technol, Frontiers Sci Ctr Materiobiol & Dynam Chem, Feringa Nobel Prize Scientist Joint Res Ctr, Key Lab Adv Mat, Shanghai 200237, Peoples R China;[2]East China Univ Sci & Technol, Frontiers Sci Ctr Materiobiol & Dynam Chem, Feringa Nobel Prize Scientist Joint Res Ctr, Joint Int Res Lab Precis Chem & Mol Engn, Shanghai 200237, Peoples R China;[3]East China Normal Univ, State Key Lab Precis Spect, Shanghai 200241, Peoples R China

年份：2023

卷号：62

期号：29

外文期刊名：ANGEWANDTE CHEMIE-INTERNATIONAL EDITION

收录：;EI(收录号：20232314200021);WOS:【SCI-EXPANDED(收录号:WOS:001002728400001)】；

基金：This work was supported by NSFC/China (21788102, 22175063, 21790361, and 92156024), Shanghai Municipal Sci. & Tech. Major Project (2018SHZDZX03), the 111 Project (B16017), Shanghai Committee of Sci. & Tech. (17520750100), Natural Science Foundation of Shanghai (19ZR1412200), and the Program for Eastern Scholar Distinguished Professor.

语种：英文

外文关键词：Dihydrophenazine; Multiple Fluorescence Emissions; Photoinduced Structural Transformation; Potential Energy Surface; Steric Hindrance

摘要：We demonstrate that a single polycyclic pi-scaffold can undergo sequential multistep excited-state structural evolution along the bent, planar, and twisted conformers, which coexist to produce intrinsic multiple fluorescence emissions in room-temperature solution. By installing a methyl or trifluoromethyl group on the ortho-site of N,N '-diphenyl-dihydrodibenzo[a,c]phenazine (DPAC), the enhanced steric effects change the fluorescence emission of DPAC from a dominant red band to well-resolved triple bands. The ultra-broadband triple emissions of ortho-substituted DPACs range from approximate to 350 to approximate to 850 nm, which is unprecedented for small fluorophores with molecular weight of <500. Ultrafast spectroscopy and theoretical calculations clearly reveal that the above dramatic changes originate from the influence of steric hindrance on the shape of excited state potential energy surface (S-1 PES). Compared to the steep S-1 PES of parental DPAC, the introduction of ortho-substituent is shown to make the path of structural evolution in S-1 wider and flatter, so the ortho-substituted derivatives exhibit slower structural transformations from bent to planar and then to twisted forms, yielding intrinsic triple emission. The results provide the proof of concept that the bent, planar, and twisted emissive states can coexist in the same S-1 PES, which greatly expand the fundamental understanding of the excited-state structural relaxation.