Molecular Spectroscopy Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan.
Ultrafast Spectroscopy Research Team, RIKEN Center for Advanced Photonics (RAP), RIKEN, 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan.
Angew Chem Int Ed Engl. 2020 Jun 8;59(24):9498-9505. doi: 10.1002/anie.202002368. Epub 2020 Apr 15.
Water around hydrophobic groups mediates hydrophobic interactions that play key roles in many chemical and biological processes. Thus, the molecular-level elucidation of the properties of water in the vicinity of hydrophobic groups is important. We report on the structure and dynamics of water at two oppositely charged hydrophobic ion/water interfaces, that is, the tetraphenylborate-ion (TPB )/water and tetraphenylarsonium-ion (TPA )/water interfaces, which are clarified by two-dimensional heterodyne-detected vibrational sum-frequency generation (2D HD-VSFG) spectroscopy. The obtained 2D HD-VSFG spectra of the anionic TPB interface reveal the existence of distinct π-hydrogen bonded OH groups in addition to the usual hydrogen-bonded OH groups, which are hidden in the steady-state spectrum. In contrast, 2D HD-VSFG spectra of the cationic TPA interface only show the presence of usual hydrogen-bonded OH groups. The present study demonstrates that the sign of the interfacial charge governs the structure and dynamics of water molecules that face the hydrophobic region.
水围绕疏水区介导疏水力相互作用，在许多化学和生物过程中发挥关键作用。因此，阐明疏水区附近水的性质具有重要意义。我们报告了两种带相反电荷的疏水离子/水界面，即四苯硼酸盐离子（TPB）/水和四苯砷盐离子（TPA）/水界面的结构和动态，这是通过二维异频检测振动和频产生（2D HD-VSFG）光谱澄清的。阴离子 TPB 界面的获得的 2D HD-VSFG 谱显示存在除通常的氢键 OH 基团之外的独特π氢键合 OH 基团，其隐藏在稳态谱中。相比之下，阳离子 TPA 界面的 2D HD-VSFG 谱仅显示存在通常的氢键 OH 基团。本研究表明，界面电荷的符号控制了面向疏水区的水分子的结构和动力学。
