Solvent effects on the electronic spectra of some mesoionic 2,3-diaryl-2H-tetrazolium-5-thiolate derivatives were investigated in thirteen pure solvents and eight water–organic solvent mixtures. In pure solvents, the solvatochromic
shifts of the mesoionic compounds are found to be mainly influenced by the AN, α and π* solvent parameters.
The relative contributions of these parameters depend on the nature of the substituents on the phenyl moieties
of the mesoionic derivatives. Thus, electron-donating substituents increase the relative contribution of both AN and α parameters but decrease the relative contribution of the π* parameter. The behavior of the mesoionic
derivatives in water–organic solvent mixtures has been explained in terms of preferential solvation. Different criteria were considered to evaluate the extent of preferential solvation in different solvent mixtures, iz. the excess function (Δν), iso-solvation point (Xiso) and preferential solvation constant (K). Three distinct preferential solvation patterns
for the mesoionic derivatives in different water–organic solvent mixtures were elucidated: negative deviation
in water–alcohol and water–Py, positive deviation in water–Me2CO and water–DMF, and a dual behavior in water–MeCN and water–Diox solvent mixtures. Molecular orbital calculations have been carried out for the mesoionic derivatives and the data correlated with the experimental results.
研究了溶剂在 13 种纯溶剂和 8 种
水有机溶剂混合物中对一些介离子 2,3-二芳基-2H-
四唑-5-
硫酸酯衍
生物电子光谱的影响。研究发现,在纯溶剂中,介离子化合物的溶度色移主要受 AN、α 和 π* 溶剂参数的影响。 这些参数的相对贡献取决于介离子衍
生物苯基上取代基的性质。因此,电子捐赠取代基会增加 AN 和 α 参数的相对贡献,但会减少 π* 参数的相对贡献。介离子衍
生物在
水-有机溶剂混合物中的行为可以用优先溶解来解释。在评估不同溶剂混合物中的优先溶解度时,考虑了不同的标准,即过量函数(Δν)、等溶点(Xiso)和优先溶解常数(K)。阐明了介离子衍
生物在不同
水-有机溶剂混合物中的三种不同的优先溶解模式:在
水-醇和
水-
吡中的负偏离,在
水-Me2CO 和
水-
DMF 中的正偏离,以及在
水-MeCN 和
水-
二氧六环溶剂混合物中的双重行为。我们对介离子衍
生物进行了分子轨道计算,并将计算结果与实验结果进行了对比。