Zhang Qiang, Chen Hailong, Wu Tianmin, Jin Tan, Pan Zhijun, Zheng Junrong, Gao Yiqin, Zhuang Wei
State Key Laboratory of Structural Chemistry , Fujian Institute of Research on the Structure of Matter , Chinese Academy of Sciences , Fuzhou , Fujian 350002 , China . Email:
Department of Chemistry , Bohai University , Jinzhou 121013 , China.
Chem Sci. 2017 Feb 1;8(2):1429-1435. doi: 10.1039/c6sc03320b. Epub 2016 Oct 14.
Water rotational dynamics in NaSCN and KSCN solutions at a series of concentrations are investigated using femtosecond infrared spectroscopy and theory. Femtosecond infrared measurements, consistent with previous NMR observations, detect that sodium slows down while potassium accelerates the water O-H bond rotation. Results of reported neutron scattering measurements, on the other hand, suggested that these two cations have similar structure-breaking effects on water, and therefore should both accelerate water rotation through the presumably dominating large-amplitude angular jump component. To explain this discrepancy, theoretical studies with both classical and models were carried out, which indicate that both ions indeed accelerate the large-amplitude angular jump rotation of the water molecules, while the observed cation specific effect originates from the non-negligible opposite impact of the sodium and potassium cations on the diffusive rotation of water molecules.
利用飞秒红外光谱和理论研究了一系列浓度的硫氰化钠和硫氰化钾溶液中的水旋转动力学。飞秒红外测量结果与先前的核磁共振观测结果一致，检测到钠会使水的O-H键旋转减慢，而钾会加速水的O-H键旋转。另一方面，已报道的中子散射测量结果表明，这两种阳离子对水具有相似的结构破坏作用，因此都应该通过可能占主导地位的大幅度角跳跃分量来加速水的旋转。为了解释这种差异，进行了经典模型和量子模型的理论研究，结果表明这两种离子确实都加速了水分子的大幅度角跳跃旋转，而观察到的阳离子特异性效应源于钠和钾阳离子对水分子扩散旋转的不可忽略的相反影响。
