Chatterjee Srijan, Deshmukh Samadhan H, Bagchi Sayan
Physical and Materials Chemistry Division, National Chemical Laboratory (CSIR-NCL), Dr. Homi Bhabha Road, Pune411008, India.
Academy of Scientific and Innovative Research (AcSIR), Ghaziabad201002, India.
J Phys Chem B. 2022 Oct 20;126(41):8331-8337. doi: 10.1021/acs.jpcb.2c06521. Epub 2022 Oct 6.
Deep eutectic solvents, consisting of heterogeneous nanodomains of hydrogen-bonded networks, have evolved into a range of viscous fluids that find applications in several fields. As viscosity is known to influence the dynamics of other neoteric solvents like ionic liquids, understanding the effect of viscosity on deep eutectic solvents is crucial to realize their full potential. Herein, we combine polarization-selective pump-probe spectroscopy, two-dimensional infrared spectroscopy, and molecular dynamics simulations to elucidate the impact of viscosity on the dynamics of an alcohol-based deep eutectic solvent, ethaline. We compare the solvent fluctuation and solute reorientation time scales in ethaline with those in ethylene glycol, an ethaline constituent. Interestingly, we find that the solute's reorientation apparently scales the bulk viscosity of the solvent, but the same is not valid for the overall solvation dynamics. Using the variations in the estimated intercomponent hydrogen bond lifetimes, we show that a dissolved solute does not sense the bulk viscosity of the deep eutectic solvent; instead, it senses domain-specific local viscosity determined by the making and breaking of the hydrogen bond network. Our results indicate that understanding the domain-specific local environment experienced by the dissolved solute is of utmost importance in deep eutectic solvents.
由氢键网络的异质纳米域组成的深共熔溶剂，已发展成为一系列在多个领域有应用的粘性流体。由于已知粘度会影响离子液体等其他新型溶剂的动力学，了解粘度对深共熔溶剂的影响对于充分发挥其潜力至关重要。在此，我们结合偏振选择性泵浦 - 探测光谱、二维红外光谱和分子动力学模拟，以阐明粘度对基于醇的深共熔溶剂乙酰胺动力学的影响。我们将乙酰胺中的溶剂涨落和溶质重取向时间尺度与乙酰胺成分之一乙二醇中的进行比较。有趣的是，我们发现溶质的重取向明显与溶剂的本体粘度成比例，但对于整体溶剂化动力学则不然。利用估计的组分间氢键寿命的变化，我们表明溶解的溶质感受不到深共熔溶剂的本体粘度；相反，它感受到由氢键网络的形成和断裂所决定的特定域局部粘度。我们的结果表明，了解溶解溶质所经历的特定域局部环境在深共熔溶剂中至关重要。
