In a recent publication by Dutta and co-workers in July 2019,(1) the authors reported a vibrational spectroscopic probe of local interactions in imidazolium-based ionic liquids (ILs) by deuteration of the C₍₂₎ position of the imidazolium ring. However, while we agree with the value of that approach, the claim that this is a new strategy is quite misleading, as our group has published several studies over the past six years,(2−6) using selective deuteration at the C₍₂₎H position and structural characterization with infrared spectroscopy (more precisely, cryogenic ion vibrational predissociation spectroscopy)(7) to characterize the local microscopic interactions and binding of ILs involving the C₍₂₎ position. Our first report in 2013 focused on common imidazolium-based ILs(2−4) and has evolved to include more complicated ILs with functionalized side groups.(5,6) The protocols for H/D exchange(8) in these samples by heating with D₂O or CD₃OD solvents were described in detail in these studies. In particular, Williams et al. suggested, in the second last paragraph of their manuscript,(1) that a new class of hydroxy-functionalized ionic liquids that display attractive cation–cation interaction(9) could be “potentially detected” with the use of the C₍₂₎D probe. In fact, this had been already done in our collaboration with Prof. Ralf Ludwig on hydroxy-functionalized systems, with our first results(5) in 2018 published in JPC Letters reporting different isomeric structures that were identified for the isolated ternary (HEMIm⁺)₂NTf₂^– complex [HEMIm⁺ = 1-(2-hydroxyethyl)-3-methylimidazolium]. The experiment involved deuteration of the imidazolium C₍₂₎H site as well as the OH group on the cation, cooling the ternary clusters to 35 K in a photodissociation mass spectrometer, and application of isomer-selective, two-color IR–IR double resonance spectroscopy. The binding motifs of these structures were identified on the basis of spectral shifts of the C₍₂₎D and OD peaks, which were supported by DFT calculations.(10,11) Since the authors did not refer to any of these papers, we herein wish to correct this oversight. At the same time, we recognize and appreciate the importance of their demonstration that C₍₂₎D substitution is effective in the structural analysis of macroscopic, condensed phase room temperature IL samples. The authors declare no competing financial interest. The authors thank Prof. James F. Wishart for bringing this to our attention. This article references 11 other publications.

中文翻译：

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关于“作为离子液体微环境探针的咪唑阳离子在C2位置的CD振动”的评论。

在Dutta及其同事于2019年7月的最新出版物中，（1）作者报告了通过对咪唑鎓环的C _（2）位置进行氘化反应，对基于咪唑鎓的离子液体（ILs）中的局部相互作用进行振动光谱探测。然而，尽管我们同意该方法的价值，但声称这是一种新策略还是很容易引起误解，因为我们小组在过去六年中发表了几项研究（2-6），使用了C选择性氘化_{（2 ）} H位置和结构特征的红外光谱学（更准确地说是低温离子振动预离解谱学）（7）来表征涉及C的IL的局部微观相互作用和结合_（2）位置。我们在2013年的第一份报告关注的是基于咪唑类的常见ILs（2-4），并逐渐发展成为包括具有功能化侧基的更复杂的ILs（5,6）。在这些研究中详细介绍了使用D ₂ O或CD ₃ OD溶剂的情况。特别是，威廉姆斯等。建议在其手稿的第二段中，（1）使用C _（2） D可以“潜在地检测到”显示出有吸引力的阳离子-阳离子相互作用的新型羟基官能化离子液体（9）。探测。实际上，这是我们与Ralf Ludwig教授在羟基官能化系统上的合作所完成的，我们的第一批结果（5）于2018年发表在JPC Letters上报告被确定为隔离三元（HEMIm不同异构结构⁺）₂ NTF ₂ ^-络合物[HEMIm ⁺ = 1-（2-羟乙基）-3-甲基咪唑]。该实验涉及对咪唑鎓C _（2） H位以及阳离子上的OH基团进行氘化，在光解质谱仪中将三元簇冷却至35 K，并应用异构体选择性，双色IR-IR双共振光谱学。这些结构的结合基序是根据C的光谱位移确定的_（2）DFT和OD峰得到了DFT计算的支持。（10,11）由于作者没有引用任何这些论文，因此我们在此希望纠正这种疏忽。同时，我们认识到并赞赏他们证明C _（2） D替代在宏观，冷凝相室温IL样品的结构分析中有效的重要性。作者宣称没有竞争性的经济利益。作者感谢James F. Wishart教授引起我们注意。本文引用了其他11种出版物。