Barik Sahadev, Chakraborty Manjari, Mahapatra Amita, Sarkar Moloy
School of Chemical Sciences, National Institute of Science Education and Research (NISER), An OCC of Homi Bhabha National Institute, Jatni, Khurda, Bhubaneswar, 752050, Odisha, India.
Centre of Interdisciplinary Science (CIS), NISER, Bhubaneswar, Jatni, Khurda, 752050, Odisha, India.
Phys Chem Chem Phys. 2022 Mar 16;24(11):7093-7106. doi: 10.1039/d1cp05010a.
With the aim of understanding the differences in the behavior of deep eutectic solvents (DESs) and room temperature ionic liquids (RTILs) in terms of their structure, dynamics, and intra- and intermolecular interactions, three different ILs and one DES having similar functionalities (hydroxyl) have been investigated by using both ensembled average and single-molecule spectroscopic techniques. Specifically, for this purpose, a choline chloride based DES (ethaline) and three hydroxyl functionalized ILs (1-(2-hydroxyethyl)-3-imidazolium bis(trifluoromethanesulfonyl)imide ([OHEMIM][NTF]), -(2-hydroxyl ethyl)--methylpyrrolidinium bis(trifluoromethanesulfonyl)imide ([OHEMPy][NTf]), and -(2-hydroxyethyl)-,-dimethylpropan-1-aminium bis(trifluoromethanesulfonyl)imide ([OHC3CH][NTf])) are employed and investigated by EPR, time-resolved fluorescence, NMR and FCS studies. Estimation of polarity through EPR spectroscopy has revealed that the hydroxyl ILs employed in these studies are hyper-polar (close to water) in nature, whereas the polarity of the DES is found to be close to those of aliphatic polyhydroxy-alcohols. Interestingly, both time-resolved fluorescence anisotropy and FCS studies on these systems have suggested that the hydroxyl ILs are more dynamically heterogeneous than the DES. More interestingly, PFG-NMR measurements have indicated that the fluid structure of ethaline is relatively more associated as compared to those of the ILs despite the fact that all the cations have the same hydroxyl functionalities. All these investigations have essentially demonstrated that, despite having similar functionalities, both the DES and hydroxyl ILs employed in the present study exhibit microscopic behaviours that are significantly different from each other, indicating the interplay of various intermolecular interactions within the constituent species in governing the behaviours of these solvent systems.
为了从结构、动力学以及分子内和分子间相互作用方面理解深共熔溶剂（DESs）和室温离子液体（RTILs）行为的差异，使用系综平均和单分子光谱技术研究了三种不同的离子液体和一种具有相似官能团（羟基）的深共熔溶剂。具体而言，为此目的，采用了基于氯化胆碱的深共熔溶剂（乙aline）和三种羟基官能化的离子液体（1-(2-羟乙基)-3-咪唑鎓双（三氟甲磺酰）亚胺（[OHEMIM][NTF]）、-(2-羟乙基)--甲基吡咯烷鎓双（三氟甲磺酰）亚胺（[OHEMPy][NTf]）和-(2-羟乙基)-,-二甲基丙-1-铵双（三氟甲磺酰）亚胺（[OHC3CH][NTf]）），并通过电子顺磁共振（EPR）、时间分辨荧光、核磁共振（NMR）和荧光相关光谱（FCS）研究进行了探究。通过EPR光谱对极性的估计表明，这些研究中使用的羟基离子液体本质上是超极性的（接近水），而深共熔溶剂的极性则与脂肪族多羟基醇的极性相近。有趣的是，对这些体系的时间分辨荧光各向异性和FCS研究均表明，羟基离子液体比深共熔溶剂具有更高的动力学异质性。更有趣的是，脉冲场梯度核磁共振（PFG-NMR）测量表明，尽管所有阳离子都具有相同的羟基官能团，但乙aline的流体结构与离子液体相比相对更具关联性。所有这些研究基本上都表明，尽管具有相似的官能团，但本研究中使用的深共熔溶剂和羟基离子液体均表现出彼此显著不同的微观行为，这表明组成物种内各种分子间相互作用在控制这些溶剂体系行为方面的相互作用。
