Department of Chemistry, University of Minnesota-Twin Cities, Minneapolis, Minnesota 55455, USA.
Doane University, 1014 Boswell Avenue, Crete, Nebraska 68333, USA.
J Chem Phys. 2017 Sep 28;147(12):124302. doi: 10.1063/1.5003908.
Fourier transform infrared and two-dimensional IR (2D-IR) spectroscopies were applied to two different silanes in three different solvents. The selected solutes exhibit different degrees of vibrational solvatochromism for the Si-H vibration. Density functional theory calculations confirm that this difference in sensitivity is the result of higher mode polarization with more electron withdrawing ligands. This mode sensitivity also affects the extent of spectral diffusion experienced by the silane vibration, offering a potential route to simultaneously optimize the sensitivity of vibrational probes in both steady-state and time-resolved measurements. Frequency-frequency correlation functions obtained by 2D-IR show that both solutes experience dynamics on similar time scales and are consistent with a picture in which weakly interacting solvents produce faster, more homogeneous fluctuations. Molecular dynamics simulations confirm that the frequency-frequency correlation function obtained by 2D-IR is sensitive to the presence of hydrogen bonding dynamics in the surrounding solvation shell.
傅里叶变换红外和二维红外（2D-IR）光谱学被应用于三种不同溶剂中的两种不同硅烷。所选溶质对 Si-H 振动表现出不同程度的振动溶剂化变色。密度泛函理论计算证实，这种敏感性差异是由于具有更多吸电子配体的更高模式极化的结果。这种模式敏感性还会影响硅烷振动所经历的光谱扩散程度，为同时优化振动探针在稳态和时间分辨测量中的灵敏度提供了一种潜在途径。通过二维红外获得的频-频相关函数表明，两种溶质都经历了相似时间尺度上的动力学过程，这与弱相互作用溶剂产生更快、更均匀的波动的图像一致。分子动力学模拟证实，二维红外获得的频-频相关函数对周围溶剂化壳中氢键动力学的存在敏感。
