Neutral Heteroleptic Lanthanide Complexes for Unravelling Host- Guest Assemblies in Organic Solvents: The Law of Mass Action Revisited
Neutral Heteroleptic Lanthanide Complexes for Unravelling Host- Guest Assemblies in Organic Solvents: The Law of Mass Action Revisited
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DOI：
10.1021/acs.inorgchem.9b00755
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发表时间：
2020-01-06
影响因子：
4.6
通讯作者：
Piguet, Claude
中科院分区：
文献类型：
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作者：
Baudet, Karine;Kale, Vishal;Piguet, Claude
镧系元素容器[Ln（β-二酮化物）（3）dig] [dig = 1-甲氧基-2-（2-甲氧基乙氧基）乙烷]与芳香族三齿N-供体配体（L）在二氯甲烷中的结合产生中性九配位杂配体[LLn（β-二酮化物）（3）]配合物，其平衡反应速率随反应伙伴的总浓度而变化。这种有问题的漂移阻止了可靠的热力学稳定常数和固有的主客体亲和力的测定。经典溶液理论将这种行为归因于非理想溶液中各种合作伙伴的活度系数的变化，而现象学方法试图将这种效应定量归因于溶剂分子在化学势的大量无辜和接触非无辜贡献者之间的某些分区。该假设最终预测了平衡反应商对所形成的[LLn（β-二酮）（3）]络合物的浓度的经验线性依赖性，对于亲脂性和核性不同的各种配体L以及对于接枝有不同的β-二酮共配体的镧系元素容器，实验支持该贡献的趋势。即使后者的线性依赖性的起源仍然是争论的主题，这项工作表明，这种方法可以利用实验学家提取可靠的热力学常数适合于分析和比较在有机溶剂中的主客体亲和力。
The binding of lanthanide containers [Ln(beta-diketonate)(3)dig] [dig = 1-methoxy-2-(2-methoxyethoxy)ethane] to aromatic tridentate N-donor ligands (L) in dichloromethane produces neutral nine-coordinate heteroleptic [LLn(beta-diketonate)(3)] complexes, the equilibrium reaction quotients of which vary with the total concentrations of the reacting partners. This problematic drift prevents the determination of both reliable thermodynamic stability constants and intrinsic host-guest affinities. The classical solution theory assigns this behavior to changes in the activity coefficients of the various partners in nonideal solutions, and a phenomenological approach attempts to quantitatively attribute this effect to some partition of the solvent molecules between bulk-innocent and contactnoninnocent contributors to the chemical potential. This assumption eventually predicts an empirical linear dependence of the equilibrium reaction quotient on the concentration of the formed [LLn(beta-diketonate)(3)] complexes, a trend experimentally supported in this contribution for various ligands L differing in lipophilicity and nuclearity and for lanthanide containers grafted with diverse beta-diketonate coligands. Even if the origin of the latter linear dependence is still the subject of debate, this work demonstrates that this approach can be exploited by experimentalists for extracting reliable thermodynamic constants suitable for analyzing and comparing host-guest affinities in organic solvents.