Orthogonal carbazole-perylene bisimide pentad: a photoconversion-tunable photosensitizer with diversified excitation and excited-state relaxation pathways
Journal
Science China Chemistry
Journal Volume
64
Journal Issue
12
Pages
2193-2202
Date Issued
2021
Author(s)
Abstract
Integrating multiple photosensitive properties into an “all-in-one” photosensitizer (PS) shows great promise for the treatment of cancers owing to synergistic effect among them. However, the development of such PSs, especially those that need a single laser source, remains a challenge. Herein, we report an orchestration of electron donors and acceptors in a propeller-like pentad, PBI-4Cz, where four carbazole (Cz) units are covalently linked to the ortho-positions of the perylene bisimide (PBI) core. Strong intramolecular donor-acceptor interaction significantly quenches the luminescence and largely extends the absorption spectra to near-infrared region. Excited-state dynamics investigated via femto- and nano-second transient absorption spectroscopy revealed exclusive charge separation of the PBI-4Cz within initial 0.5 ps when photoexcited regardless of which intermediate is involved. Energy dissipation of the resulting charge-separated state (PBI•−-4Cz•−) is subjected to the toggle between intersystem-crossing toward excited triplet states and charge recombination toward ground states. Relative importance of the two pathways can be tuned by micro-environmental polarity, which endows PBI-4Cz remarkable performances of singlet-oxygen generation (>90.0%) in toluene and photothermal conversion (∼28.6%) in DMSO. Harnessing intrinsic photostability and excited-state processes of heavy-atom-free PBI derivatives not only holds a promise for multifunctional phototheranostics, but also provides a prototype for designing high-performance PSs with tunable photoconversion pathways. [Figure not available: see fulltext.] © 2021, Science China Press and Springer-Verlag GmbH Germany, part of Springer Nature.
Subjects
charge recombination; charge separation; perylene bisimide derivatives; photosensitizers; singlet oxygen generation
SDGs
Other Subjects
Absorption spectroscopy; Energy dissipation; Excited states; Gas generators; Ground state; Infrared devices; Oxygen; Polycyclic aromatic hydrocarbons; Separation; Charge recombinations; Charge-separation; Excitation state; Performance; Perylene bisimide derivative; Perylene bisimides; Photoconversion; Photosensitiser; Singlet oxygen generation; Tunables; Photosensitizers
Type
journal article