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Solvatochromic Parameters of Deep Eutectic Solvents: Effect of Different Carboxylic Acids as Hydrogen Bond Donor
Journal of Chemical & Engineering Data ( IF 2.6 ) Pub Date : 2020-01-06 , DOI: 10.1021/acs.jced.9b00872
Amos K. Dwamena 1 , Douglas E. Raynie 1
Affiliation  

The physicochemical properties of carboxylic acid-based deep eutectic solvents (DESs) were measured by solvatochromic probes: Nile red, N,N-diethyl-4-nitroaniline, and 4-nitroaniline. UV–vis absorbance of these probes was computed with temperature in the range of 298.15 to 318.15 K. By increasing temperature, the normalized polarity of DESs stayed linear except for [Ch]Cl:butyric acid (1:3) and [Ch]Cl:caprylic acid (1:2), which had a modest shift in the maximum wavelength between T = (308.15 to 318.15) K. Changes in the normalized polarity parameter of DESs demonstrated an interesting trend, and it confirms that alkyl chain length of the hydrogen bond donor (HBD) affects the solvation microsphere of the solute–solvent interaction. Also, dipolarity/polarizability (π*) and hydrogen bond acidity (α) decrease with increasing alkyl chain length confirming the significant contribution of HBDs to Kamlet–Taft parameters. Interestingly, the π* and α parameters of DESs did not change significantly and seem to be independent of temperature. In addition, density functional theory was used to extend our understanding on how alkyl chain length of HBD affects charge transfer in the DESs. In summary, both solvatochromic molecular probes and density functional theory are effective methods for studying polarity parameters and charge transfer, respectively, for DESs with varying alkyl chain length of the hydrogen bond donor.

中文翻译:

深共熔溶剂的溶剂变色参数:不同羧酸作为氢键供体的影响

通过溶剂化变色探针:尼罗红,NN-二乙基-4-硝基苯胺和4-硝基苯胺,测量了基于羧酸的深共熔溶剂(DES)的理化性质。在298.15至318.15 K的温度范围内计算这些探针的UV-vis吸光度。通过提高温度,除[Ch] Cl:丁酸(1:3)和[Ch] Cl以外,DES的归一化极性保持线性。 :辛酸(1:2),其最大波长在T之间有适度的偏移=(308.15至318.15)K。DESs的归一化极性参数变化显示出一个有趣的趋势,它证实了氢键供体(HBD)的烷基链长影响溶质与溶剂相互作用的溶剂化微球。另外,随着烷基链长度的增加,偶极/极化率(π*)和氢键酸度(α)降低,这证实了HBD对Kamlet-Taft参数的显着贡献。有趣的是,DES的π*和α参数没有显着变化,似乎与温度无关此外,使用密度泛函理论扩展了我们对HBD烷基链长度如何影响DES中电荷转移的理解。总而言之,溶剂变色分子探针和密度泛函理论都是研究极性参数和电荷转移的有效方法,分别用于氢键供体烷基链长度不同的DES。
更新日期:2020-01-07
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