温度对LiCl/(DMSO-H<sub>2</sub>O)溶液影响的2D-IR研究

doi:10.3964/j.issn.1000-0593(2020)05-1436-06

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Abstract The study of the solution, especially metal ions in binary solutions, is an important part in the fields of chemical engineering and environment. The traditional analysis would mainly be the use of one-dimensional Infrared spectroscopy or Raman spectroscopy. However, the resolution ratio of the methods is low, and spectral peaks overlap is serious usually, which will lead to the errors. Two-dimensional infrared spectroscopy (2D-IR) has its advantage, in this article 2D-IR and density functional theory have been combined to analysis of the cluster in solution, and the result could satisfactorily be obtained. Firstly using Fourier transform infrared spectroscopy (FTIR) for DMSO-H₂O and Li⁺/(DMSO-H₂O) have been measured in the range of 4 000～400 cm^-1 with temperature as external disturbance. One-dimensional infrared spectra of S═O double bond could be obtained by normalization of the data. It could be found that the S═O of DMSO shifted to red when water was added, and their intensity of S═O infrared vibration would increase with the raise of temperature. The intensity of S═O double bond would decrease with the addition of Li⁺, moreover the overlap of peaks was serious, which would influence to distinguish. 2D-IR would be used to analyze, include its type, dynamic change, change order of molecule in S═O double bond and the effect of lithium ion on the solution. And the changing rule could be obtained. The cluster structures have been optimized and analyzed by using density functional theory calculation, and the results could prove that it is useful and feasible. Moreover, both the theoretical calculation and experimental have been used in the verification of the clusters in the solution, and these would expand the researchregion. Therefore, when discussed forDMSO-H₂O and LiCl/(DMSO-H₂O)by using 2D-IR with the temperature change. The results of synchronous 2D-IR have shown that there are four automatic peaks near 1 010, 1 045, 990 and 1 020 cm^-1 when temperature is perturbed, which indicates that in S═O bond exists methyl vibration, DMSO·H₂O，monomer and dimer DMSO molecular clusters. Furthermore, the DMSO·H₂O with frequency of 1 010 cm^-1 changed earlier has been discovered in asynchronous 2D-IR, and it was speculated that the [Li(DMSO-H₂O)]⁺ is more sensitive to temperature. By combining density functional theory (DFT) and 2D-IR analysis, the forms of clusters could be ascribed, and the problem of overlap or unobvious peaks in one-dimensional infrared spectroscopy could be solved, and more chemical information would be obtained in a better way.

Key words：Two-dimensional infrared spectroscopy; Binary solutions; Density functional theory; Solvation

Received: 2019-03-13 Accepted: 2019-07-21

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https://www.gpxygpfx.com/EN/10.3964/j.issn.1000-0593(2020)05-1436-06 OR https://www.gpxygpfx.com/EN/Y2020/V40/I05/1436