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Efficient Intersystem Crossing in the Tröger's Base Derived From 4‐Amino‐1,8‐naphthalimide and Application as a Potent Photodynamic Therapy Reagent
Author(s) -
Zhao Yingjie,
Chen Kepeng,
Yildiz Elif Akhuseyin,
Li Shujing,
Hou Yuqi,
Zhang Xue,
Wang Zhijia,
Zhao Jianzhang,
Barbon Antonio,
Yaglioglu Halime Gul,
Wu Huijian
Publication year - 2020
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201905248
Subject(s) - intersystem crossing , photochemistry , ultrafast laser spectroscopy , chemistry , triplet state , quantum yield , excited state , free base , spectroscopy , singlet state , fluorescence , atomic physics , molecule , organic chemistry , physics , salt (chemistry) , quantum mechanics
Intersystem crossing (ISC) was observed for naphthalimide (NI)‐derived Tröger's base, and the ISC was confirmed to occur by a spin‐orbital charge‐transfer (SOCT) mechanism. Conventional electron donor/acceptor dyads showing SOCT‐ISC have semirigid linkers. In contrast, the linker between the two chromophores in Tröger's base is rigid and torsion is completely inhibited, which is beneficial for efficient SOCT‐ISC. Femtosecond transient absorption (TA) spectra demonstrated charge‐separation and charge‐recombination‐induced ISC processes. Nanosecond TA spectroscopy confirmed the ISC, and the triplet state is long‐lived (46 μs, room temperature). The ISC quantum yield is dependent on solvent polarity (8–41 %). The triplet state was studied by pulsed‐laser‐excited time‐resolved EPR spectroscopy, and both the NI‐localized triplet state and triplet charge‐transfer state were observed, which is in good agreement with the spin‐density analysis. The Tröger's base was confirmed to be a potent photodynamic therapy reagent with HeLa cells (EC 50 =5.0 n m ).