Hydrogen-bond facilitated intramolecular proton transfer in excited state and fluorescence quenching mechanism of flavonoid compounds in aqueous solution

Publication date: 15 March 2020Source: Journal of Molecular Liquids, Volume 302Author(s): Yingqian Zhong, Yan Chen, Xia Feng, Yan Sun, Shen Cui, Xiaozeng Li, Xiaoning Jin, Guangjiu ZhaoAbstractThe density functional theory (DFT) and time-dependent density functional theory (TDDFT) were performed to investigate the ground state and excited state hydrogen-bonding dynamics of flavonoid in hydrogen donating aqueous solution. We demonstrated that the intermolecular hydrogen bond C=O•••H-O between flavonoid and water molecules is significantly strengthened in the electronically excited-state upon photoexcitation of the hydrogen-bonded complex. The radiationless deactivation via intramolecular proton transfer in excited state (ESIPT) can be facilitated by the hydrogen bond strengthening in the excited state. At the same time, quantum yields of the excited-state deactivation via fluorescence are correspondingly decreased. The total fluorescence of flavonoid in polar protic solvents can be drastically quenched by hydrogen bonding. As a consequence, we propose a fluorescence modulation mechanism by hydrogen bonding to explain fluorescence emissions of flavonoid in hydrogen- bonding solvents and no hydrogen-bonding solvents. Given that water molecules have anomalous properties that are different from other small organic molecules that form hydrogen bonds with flavonoids, this theoretical study has reference significance for the development of in vivo probes. Hopefully, the newly p...
Source: Journal of Molecular Liquids - Category: Molecular Biology Source Type: research