Molecular recognition probes of solvation thermodynamics in solvent mixtures
Molecular recognition probes of solvation thermodynamics in solvent mixtures
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DOI：
10.1039/c1ob06083j
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发表时间：
2011-01-01
影响因子：
3.2
通讯作者：
Vinter, Jeremy G.
中科院分区：
文献类型：
--
作者：
Amenta, Valeria;Cook, Joanne L.;Vinter, Jeremy G.
利用四种分子印迹探针进行了高通量的紫外-可见光谱实验，所述探针由两种氢键受体，三正丁基氧化膦和N，N '-双（2-乙基己基）乙酰胺，以及两种氢键供体，4-苯基偶氮苯酚和4-硝基苯酚的组合制成。在极性和非极性溶剂，二正己基醚和正辛烷的混合物中，分别测定了每个探针系统中所涉及的1：1氢键相互作用的缔合常数。所有四个系统都观察到类似的行为。当极性溶剂的浓度较低时，缔合常数与纯正辛烷中观察到的缔合常数相同。然而，一旦极性溶剂的浓度超过阈值，缔合常数与二正己基醚的浓度线性下降。混合物中的选择性溶剂化可以基于系统中多个竞争平衡之间的竞争来理解。在这种情况下，溶剂化热力学由醚对氢键供体的溶剂化的竞争主导。对于极性较大的溶质4-硝基苯酚，与极性较小的溶质4-苯基偶氮苯酚相比，选择性溶剂化开始于较低浓度的极性溶剂。因此，包含多种溶质和多种溶剂的体系的形态和性质可以从氢键性质和各个官能团的浓度来估计。
High-throughput UV-Vis experiments using four molecular recognition-based probes, made by the combination of two hydrogen bond acceptors, tri-n-butylphosphine oxide and N,N'-bis(2-ethylhexyl)acetamide, and two hydrogen bond donors, 4-phenylazophenol and 4-nitrophenol, were performed. The association constants for the 1 : 1 H-bond interaction involved in each probe system were measured in mixtures of a polar and non-polar solvent, di-n-hexyl ether and n-octane, respectively. Similar behaviour was observed for all four systems. When the concentration of the polar solvent was low, the association constant was identical to that observed in pure n-octane. However, once the concentration of the polar solvent exceeded a threshold, the association constant decreased linearly with the concentration of di-n-hexyl ether. Selective solvation in mixtures can be understood based on the competition between the multiple competing equilibria in the system. In this case, solvation thermodynamics are dominated by competition of the ether for solvation of H-bond donors. For the more polar solute, 4-nitrophenol, the selective solvation starts at lower concentrations of the polar solvent compared with the less polar solute, 4-phenylazophenol. Thus the speciation and hence the properties of systems containing multiple solutes and multiple solvents can be estimated from the H-bond properties and the concentrations of the individual functional groups.