Ultrafast vibrational dynamics of a solute correlates with dynamics of the solvent
Ultrafast vibrational dynamics of a solute correlates with dynamics of the solvent
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DOI：
10.1063/5.0061770
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发表时间：
2021-10-07
影响因子：
4.4
通讯作者：
Kubarych, Kevin J.
中科院分区：
文献类型：
--
作者：
Crum, Vivian F.;Kiefer, Laura M.;Kubarych, Kevin J.
用二维红外光谱(2D-IR)研究了环戊二烯基锰(CMT)金属配合物在一系列直链烷基腈中的光谱动力学。2D-IR光谱通过光谱扩散提供了溶剂化动力学的直接读数，探测了由溶剂环境的波动引起的频率相关性的衰减。2D-IR同时监测了激发振动之间的分子内振动能量再分配(IVR)，这也可以通过光谱密度而不是溶剂化作用下的动力学摩擦来受溶剂的影响。在这里，我们报告说，CMT振动探针在光谱扩散和IVR时间尺度上都显示出溶剂依赖性，其中每个时间尺度都随着烷基链长的增加而减慢。为了评估溶质-溶剂相互作用与主体溶剂性质的关联程度，我们将我们的结果与由光学克尔效应(OKE)光谱获得的低频动力学进行了比较--在相同的丁腈溶剂系列上。我们发现我们的光谱扩散结果与OKE的取向动力学时间尺度之间有很好的相关性。我们还发现了IVR时间尺度与在90厘米(-1)能量差下估计的低频光谱密度的幅度之间的相关性，对应于羰基探针的两个强振动模式之间的间隙。2D-IR和OKE在凝聚相动力学方面提供了互补的观点，这些发现提供了实验证据，至少在动力学关联的水平上，溶质振动动力学的某些方面可以从溶液的性质中推断出来
Two-dimensional infrared (2D-IR) spectroscopy is used to measure the spectral dynamics of the metal carbonyl complex cyclopentadienyl manganese tricarbonyl (CMT) in a series of linear alkyl nitriles. 2D-IR spectroscopy provides direct readout of solvation dynamics through spectral diffusion, probing the decay of frequency correlation induced by fluctuations of the solvent environment. 2D-IR simultaneously monitors intramolecular vibrational energy redistribution (IVR) among excited vibrations, which can also be influenced by the solvent through the spectral density rather than the dynamical friction underlying solvation. Here, we report that the CMT vibrational probe reveals solvent dependences in both the spectral diffusion and the IVR time scales, where each slows with increased alkyl chain length. In order to assess the degree to which solute-solvent interactions can be correlated with bulk solvent properties, we compared our results with low-frequency dynamics obtained from optical Kerr effect (OKE) spectroscopy-performed by others-on the same nitrile solvent series. We find excellent correlation between our spectral diffusion results and the orientational dynamics time scales from OKE. We also find a correlation between our IVR time scales and the amplitudes of the low-frequency spectral densities evaluated at the 90-cm(-1) energy difference, corresponding to the gap between the two strong vibrational modes of the carbonyl probe. 2D-IR and OKE provide complementary perspectives on condensed phase dynamics, and these findings provide experimental evidence that at least at the level of dynamical correlations, some aspects of a solute vibrational dynamics can be inferred from properties of the solvent.Published under an exclusive license by AIP Publishing