Exploiting radical-pair intersystem crossing for maximizing singlet oxygen quantum yields in pure organic fluorescent photosensitizers

Xuanhang Wang; Yucong Song; Guocui Pan; Wenkun Han; Boyu Wang; Li Cui; Huili Ma; Zhongfu An; Zhigang Xie; Bin Xu; Wenjing Tian

doi:10.1039/D0SC03128C

Exploiting radical-pair intersystem crossing for maximizing singlet oxygen quantum yields in pure organic fluorescent photosensitizers†

Xuanhang Wang,^a Yucong Song,^b Guocui Pan,^a Wenkun Han,^a Boyu Wang,^a Li Cui,^d Huili Ma,^c Zhongfu An,

^c Zhigang Xie,

*^b Bin Xu

*^a and Wenjing Tian

^a

Author affiliations

* Corresponding authors

^a State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Qianjin Street No. 2699, Changchun 130012, China
E-mail: xubin@jlu.edu.cn

^b State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, PR China
E-mail: xiez@ciac.ac.cn

^c Key Laboratory of Flexible Electronics (KLOFE), Institute of Advanced Materials (IAM), Nanjing Tech University (NanjingTech), 30 South Puzhu Road, Nanjing 211816, China

^d Department of Neurology, First Hospital of Jilin University, Changchun, PR China

Abstract

Fluorescent photosensitizers (PSs) often encounter low singlet oxygen (¹O₂) quantum yields and fluorescence quenching in the aggregated state, mainly involving the intersystem crossing process. Herein, we successfully realize maximizing ¹O₂ quantum yields of fluorescent PSs through promoting radical-pair intersystem crossing (RP-ISC), which serves as a molecular symmetry-controlling strategy of donor–acceptor (D–A) motifs. The symmetric quadrupolar A–D–A molecule PTP exhibits an excellent ¹O₂ quantum yield of 97.0% with bright near-infrared fluorescence in the aggregated state. Theoretical and ultrafast spectroscopic studies suggested that the RP-ISC mechanism dominated the formation of the triplet for PTP, where effective charge separation and an ultralow singlet–triplet energy gap (0.01 eV) enhanced the ISC process to maximize ¹O₂ generation. Furthermore, in vitro and in vivo experiments demonstrated the dual function of PTP as a fluorescent imaging agent and an anti-cancer therapeutic, with promising potential applications in both diagnosis and theranostics.

Chemical Science

Exploiting radical-pair intersystem crossing for maximizing singlet oxygen quantum yields in pure organic fluorescent photosensitizers†

Abstract

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Exploiting radical-pair intersystem crossing for maximizing singlet oxygen quantum yields in pure organic fluorescent photosensitizers

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