Solvent effects on chelate cooperativity
Solvent effects on chelate cooperativity
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DOI：
10.1039/c1sc00635e
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发表时间：
2012-01-01
期刊：
影响因子：
8.4
通讯作者：
Turega, Simon M.
中科院分区：
文献类型：
--
作者：
Hunter, Christopher A.;Misuraca, Maria Cristina;Turega, Simon M.
高通量紫外/维斯吸收滴定已被用来验证120种不同的锌卟啉-吡啶络合物的性质，含有零至四个额外的分子内氢键相互作用。使用化学双突变体循环来测量每个复合物中每个H-键的自由能贡献，从而确定分子内相互作用的有效摩尔浓度（EM）。实验已经在1，1，2，2-四氯乙烷（TCE）和以前在甲苯中进行。对于酯-酚氢键，分子间氢键的强度不随溶剂而变化，形成分子内相互作用的EM值也与溶剂无关。分子间膦酸酯二酯-苯酚H-键在TCE中比酯-苯酚H-键强一个数量级，在甲苯中强两个数量级。然而，分子间相互作用强度的差异并不完全表现在分子内相互作用中。因此，在TCE中测得的EM值比在甲苯中测得的相同络合物的值大一个数量级。这表明，在合作识别界面中可能存在一些内部补偿，其中更强的相互作用导致更有组织的结构，从而降低EM的价值。也有证据表明，由于在复杂的溶剂化壳的细节的差异结构的具体影响。
High-throughput UV/Vis absorption titrations have been used to characterise the properties of 120 different zinc porphyrin-pyridine complexes that contain between zero and four additional intramolecular H-bond interactions. Chemical double mutant cycles were used to measure the free energy contribution of each H-bond in each complex and hence determine the effective molarities (EM) for the intramolecular interactions. The experiments have been carried out in 1,1,2,2-tetrachloroethane (TCE) and previously in toluene. For an ester-phenol H-bond, the strength of the intermolecular H-bond does not change with solvent, and the values of EM for formation of intramolecular interactions are also solvent-independent. Intermolecular phosphonate diester-phenol H-bonds are one order of magnitude stronger than ester-phenol H-bonds in TCE and two orders of magnitude stronger in toluene. However, the differences in intermolecular interaction strength are not fully expressed in the intramolecular interactions. Thus the values of EM measured in TCE are up an order of magnitude larger than the values measured for the same complexes in toluene. This suggests that there may be some internal compensation in cooperative recognition interfaces, where stronger interactions lead to more organised structures reducing the value of EM. There is also evidence of structure specific effects due to differences in the details of the solvation shells of the complexes.