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.
Bibliographical noteFunding Information:
The authors gratefully acknowledge partial support from the National Science Foundation under Grant Nos. CHE-0847356 and CHE-1464416 (to A.M.M.), the National Natural Science Foundation of China under Grant No. 21533003, and the National Institutes of Health under Grant No. GM46376 (to J.G.). C.M.O. and I.C.S. were supported by a National Science Foundation Graduate Student Research Fellowship Grant No. 00039202. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.
© 2017 Author(s).