ZnCl2-乙二醇二元体系的结构特性和共晶成分的特点,Physical Chemistry Chemical Physics

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ZnCl2-乙二醇二元体系的结构特性和共晶成分的特点
Physical Chemistry Chemical Physics ( IF 2.9 ) Pub Date : 2021-5-13 , DOI: 10.1039/d1cp00573a
Payam Kalhor _{1,

2,

3,

4,

5} , Khashayar Ghandi _{2,

6,

7,

8} , Hamad Ashraf _{1,

2,

3,

4,

5} , Zhiwu Yu _{1,

2,

3,

4,

5}

Affiliation

ATR-FTIR 光谱在一系列具有广泛组成（摩尔比为 1:1.5–1:14）的 ZnCl _{2 –}乙二醇 (EG) 混合物上进行，包括稳定的 ZnCl ₂ –4EG 低共熔溶剂(DES) 组成，以探索光谱变化、结构异质性和氢键 (H 键) 特性。为了提高光谱的分辨率，采用了过量吸收和二维相关光谱。在最初的红外光谱中，确定了一个准等吸收点，表明添加 ZnCl ₂对 EG 微结构的主要干扰是形成一个独特的复合物。进一步的分析揭示了从 EG 四聚体到 ZnCl ₂的主要转化过程–4EG 复合体。还发现随着EG含量的增加，负电荷越来越多地转移到ZnCl ₂，导致Zn ← O配位键的加强和Zn-Cl键的减弱并最终解离。关于 ZnCl ₂ –4EG DES，观察到几个无与伦比的特异性。结果表明，ZnCl ₂最大程度地破坏了纯EG的氢键网络，导致EG二聚体和三聚体的产量最高。此外，与其他成分相比，ZnCl ₂–4EG DES 显示盐的负电荷、Zn-Cl 键的长度和 Zn ← O 配位键的强度突然增加。所有这些都意味着与其他混合物相比，EG中 ZnCl ₂在共晶组合物中的最强的分子间相互作用和最高的溶剂化，导致超稳定的液体混合物。这项工作提供了对深共晶溶剂的结构和相互作用特性的物理见解。

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The structural properties of a ZnCl2–ethylene glycol binary system and the peculiarities at the eutectic composition

ATR-FTIR spectroscopy was performed on a series of ZnCl₂–ethylene glycol (EG) mixtures with a wide-range of compositions (1 : 1.5–1 : 14 in molar ratios), involving the stable ZnCl₂–4EG deep-eutectic solvent (DES) composition, to explore the spectral variations, structural heterogeneity, and hydrogen bonding (H-bonding) properties. To enhance the resolution of the spectra, excess absorption and two-dimensional correlation spectroscopies were employed. In the initial IR spectra, a quasi-isosbestic point was identified, signaling that the major disturbance on EG microstructures by adding ZnCl₂ is to form a distinct complex. Further analysis uncovered the main transformation process to be from the EG tetramer to the ZnCl₂–4EG complex. It was also found that as the EG content increases, negative charge increasingly transfers to ZnCl₂, resulting in the strengthening of the Zn ← O coordination bonds and the weakening and finally dissociation of Zn–Cl bonds. Regarding the ZnCl₂–4EG DES, several incomparable specificities were observed. It was found that ZnCl₂ destructed the H-bonding network of pure EG to the largest extent, resulting in the highest production of the dimer and trimer of EG. Moreover, in comparison with other compositions, the ZnCl₂–4EG DES showed abrupt increases in the negative charge of the salt, the length of the Zn–Cl bond, and the strength of the Zn ← O coordination bond. All these imply the strongest intermolecular interactions and the highest solvation of ZnCl₂ in EG at the eutectic composition compared to those of other mixtures, resulting in a super-stable liquid mixture. The work provides physical insights into the structural and interactive properties of deep-eutectic solvents.

更新日期：2021-06-02

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