Shimizu Toshihiko, Yoshikawa Shunpei, Hashimoto Kenro, Miyazaki Mitsuhiko, Fujii Masaaki
Chemical Resources Laboratory, Tokyo Institute of Technology , 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan.
J Phys Chem B. 2015 Feb 12;119(6):2415-24. doi: 10.1021/jp507222n. Epub 2014 Sep 24.
The geometries and energetics of the ground and lower-lying singlet excited states S0, La, and Lb of 1-naphthol (NpOH)-(NH3)n (n = 0-5) clusters have been computed using density functional theory (DFT) and time-dependent density functional theory (TD-DFT) methods. Cluster size dependence of the excited state proton transfer (ESPT) reaction was investigated by the vertical transitions from the geometries that can be populated in the molecular beam experiments. For the n = 3 and 4 clusters, the proton-transferred geometries cannot be accessible without significant geometrical rearrangement from the initially populated isomers. For the n = 5 clusters, the proton-transferred structure is found in the La excited state of the isomer that can be populated in the beam. Thus, ESPT is possible by the optically prepared Lb state via internal conversion to La. We concluded that the threshold cluster size of ESPT is n = 5 under the experimental condition with low excess energy.
利用密度泛函理论（DFT）和含时密度泛函理论（TD-DFT）方法计算了1-萘酚（NpOH）-(NH₃)ₙ（n = 0 - 5）团簇基态及较低单重激发态S₀、La和Lb的几何结构与能量。通过分子束实验中可能出现的几何结构的垂直跃迁，研究了激发态质子转移（ESPT）反应对团簇尺寸的依赖性。对于n = 3和4的团簇，若不经过从初始占据异构体的显著几何重排，质子转移后的几何结构是无法达到的。对于n = 5的团簇，在束流中可占据的异构体的La激发态中发现了质子转移结构。因此，通过光制备的Lb态经内转换至La态可实现ESPT。我们得出结论，在低过剩能量的实验条件下，ESPT的阈值团簇尺寸为n = 5。
