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Excited state proton transfer in the triplet state of 8-hydroxy-5-nitroquinoline: a transient absorption and
Ran Wang1, Fengjin Zhang1, Xinghang Pan1
1Department of Chemistry, Zhejiang Sci-Tech University, Hangzhou, 310018, China. jenniexue@zstu.edu.cn.
Abstract:
8-Hydroxy-5-nitroquinoline (NO2-QN-OH) is an antimicrobial, anti-inflammatory and anticancer agent, and has been approved for use in the treatment of diseases. Its photosensitivity, however, cannot be overlooked. The photochemistry of 8-hydroxy-5-nitroquinoline in acetonitrile is investigated using transient absorption and time-resolved resonance Raman spectroscopies. By identifying the short-lived intermediates during the photoreaction, it is clear that the T state NO2-QN-OH is generated in 0.8 ps via an ultrafast ISC, followed by the IC in 8.5 ps to produce the T1 state. In neat acetonitrile, the T1 state NO2-QN-OH undergoes intramolecular proton transfer and tautomerizes to form T1 state NO2-QNH-O. To our knowledge, this is the first time that the intramolecular excited state proton transfer of hydroxyl-quinolines in an aprotic polar solvent is observed.
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