Enthalpy-entropy compensation reveals solvent reorganization as a driving force for supramolecular encapsulation in water
Enthalpy-entropy compensation reveals solvent reorganization as a driving force for supramolecular encapsulation in water
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DOI：
10.1021/ja075975z
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发表时间：
2008-03-05
影响因子：
15
通讯作者：
Raymond, Kenneth N.
中科院分区：
文献类型：
--
作者：
Leung, Dennis H.;Bergman, Robert G.;Raymond, Kenneth N.
手性自组装的M4L6宿主组装体已被证明是在极性溶剂中包封一系列客体的合适宿主，从简单的有机铵阳离子到更复杂的有机金属物种。这种分子识别过程在宿主腔内产生高度选择性的反应性。为了了解驱动分子识别过程的因素，采用范霍夫分析方法确定了一系列质子化和氟化铱客体在各种极性溶剂中的包封标准热力学参数。这些客体的封装过程表现出焓熵补偿效应。在水和甲醇等溶剂中，误差分析表明这种行为的化学来源。相反，在极性非质子溶剂（如二甲基亚砜）中对这种补偿行为的误差分析表明，这种相关性是由于范霍夫分析中焓和熵项之间的内在相关性所固有的伪像。客体在极性非质子溶剂（如水）中的封装似乎是由客体的初始溶解和溶液中氢键网络的重排所驱动的。从简单的冠醚到复杂的酶配体相互作用，这种行为与水溶液中其他合成的和天然的主-客体和分子识别过程具有共同的特征。
A chiral self-assembled M4L6 host assembly has been shown to be a suitable host for the supramolecular encapsulation of a series of guests in polar solvents, ranging from simple organic ammonium cations to more complex organometallic species. This molecular recognition process creates highly selective reactivity within the host cavity. In order to understand the factors driving the molecular recognition process, the standard thermodynamic parameters for encapsulation were determined for a series of protiated and fluorinated iridium guests in a variety of polar solvents using van't Hoff analysis. The encapsulation process for these guests exhibited enthalpy-entropy compensation effects. In solvents such as water and methanol, error analysis suggests a chemical origin for this behavior. In contrast, error analysis of this compensation behavior in polar aprotic solvents such as dimethyl sulfoxide reveals that this correlation is due to an artifact inherent in the intrinsic correlation between the enthalpy and entropy terms in the van't Hoff analysis. Guest encapsulation in polar aprotic solvents such as water appears to be driven by initial desolvation of the guest with concomitant rearrangement of the hydrogen bond networks in solution. This behavior shares common characteristics with other synthetic and natural host-guest and molecular recognition processes in aqueous solution, ranging from simple crown ether to complex enzyme-ligand interactions.