Shimizu Toshihiko, Hashimoto Kenro, Hada Masahiko, Miyazaki Mitsuhiko, Fujii Masaaki
Laboratory for Chemistry and Life Science, Institute for Innovative Research, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan.
Phys Chem Chem Phys. 2018 Jan 31;20(5):3265-3276. doi: 10.1039/c7cp05247b.
Geometries and infrared (IR) spectra in the mid-IR region of phenol-(ammonia) (PhOH-(NH)) (n = 0-10) clusters have been studied using density functional theory (DFT) to investigate the critical number of solvent molecules necessary to promote ground-state proton transfer (GSPT). For n ≤ 8 clusters, the most stable isomer is a non-proton-transferred (non-PT) structure, and all isomers found within 1.5 kcal mol from it are also non-PT structures. For n = 9, the most stable isomer is also a non-PT structure; however, the second stable isomer is a PT structure, whose relative energy is within the experimental criterion of population (0.7 kcal mol). For n = 10, the PT structure is the most stable one. We can therefore estimate that the critical size of GSPT is n = 9. This is confirmed by the fact that these calculated IR spectra are in good accordance with our previous experimental results of mid-IR spectra. It is demonstrated that characteristic changes of the ν and ν bands in the skeletal vibrational region provide clear information that the GSPT reaction has occurred. It was also found that the shortest distance between the π-ring and the solvent moiety is a good indicator of the PT reaction.
利用密度泛函理论（DFT）研究了苯酚 -（氨）（PhOH -（NH））（n = 0 - 10）团簇在中红外区域的几何结构和红外（IR）光谱，以研究促进基态质子转移（GSPT）所需的溶剂分子临界数量。对于n≤8的团簇，最稳定的异构体是未发生质子转移的（非PT）结构，且在其1.5千卡/摩尔范围内发现的所有异构体也都是非PT结构。对于n = 9，最稳定的异构体同样是一种非PT结构；然而，第二稳定的异构体是一种PT结构，其相对能量在实验丰度标准（0.7千卡/摩尔）范围内。对于n = 10，PT结构是最稳定的。因此，我们可以估计GSPT的临界尺寸为n = 9。这些计算得到的红外光谱与我们之前的中红外光谱实验结果高度吻合，这证实了这一点。结果表明，骨架振动区域中ν和ν带的特征变化提供了GSPT反应已经发生的明确信息。还发现π环与溶剂部分之间的最短距离是PT反应的一个良好指标。
