Dipartimento di Chimica 'Paolo Corradini', Università di Napoli Federico II, Complesso Universitario di M.S. Angelo , via Cintia, 80126 Napoli, Italy.
J Phys Chem B. 2013 Dec 19;117(50):16165-73. doi: 10.1021/jp406301p. Epub 2013 Dec 5.
The excited state proton transfer (ESPT) reaction taking place between 7-hydroxy-4-(trifluorometyl)coumarin and 1-methylimidazole, recently experimentally characterized, has been here considered as a case study to illustrate the possibility of using theoretical approaches rooted in density functional theory (DFT) and time-dependent DFT (TD-DFT) for the description of complex reactions occurring at the excited state. In particular, beside identifying all stable species occurring at the ground and excited state during the ESPT reaction, a quantitative characterization of their photophysical properties, such as absorption and emission, is obtained by properly including solvent effects. More interestingly, a computational protocol enabling one to locate possible reaction pathways for the ESPT is here proposed. This protocol is based on the use of density based indices purposely developed to characterize the properties of vertical and relaxed excited states which allow one to discriminate the most favorable reaction paths on potential energy surfaces that are in the case of ESPT intrinsically very flat and difficult to characterize based on sole energy criteria, thus opening a new scenario for the description of photoinduced proton transfer reactions.
7-羟基-4-(三氟甲基)香豆素和 1-甲基咪唑之间发生的激发态质子转移 (ESPT) 反应最近已被实验证实，本研究将其作为案例研究，以说明基于密度泛函理论 (DFT) 和含时密度泛函理论 (TD-DFT) 的理论方法在描述复杂的激发态反应方面的可能性。具体而言，除了确定 ESPT 反应过程中在基态和激发态下所有稳定的物种外，还通过适当考虑溶剂效应，对其光物理性质（如吸收和发射）进行了定量描述。更有趣的是，本研究提出了一种用于确定 ESPT 可能反应途径的计算方案。该方案基于使用专门开发的基于密度的指数，用于描述垂直和弛豫激发态的性质，这些指数可以在势能面上区分最有利的反应路径，对于 ESPT 而言，由于其内在非常平坦，因此仅基于能量标准很难对其进行特征描述，从而为描述光诱导质子转移反应开辟了新的场景。
