Leung Dennis H, Bergman Robert G, Raymond Kenneth N
Department of Chemistry, University of California, Berkeley, California 94720-1460, USA.
J Am Chem Soc. 2008 Mar 5;130(9):2798-805. doi: 10.1021/ja075975z. Epub 2008 Feb 8.
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 protic 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.
一种手性自组装的M4L6主体组装体已被证明是一种合适的主体，可在极性溶剂中对一系列客体进行超分子包封，这些客体从简单的有机铵阳离子到更复杂的有机金属物种不等。这种分子识别过程在主体腔内产生了高度选择性的反应性。为了理解驱动分子识别过程的因素，使用范特霍夫分析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。这些客体的包封过程表现出焓-熵补偿效应。在水和甲醇等溶剂中，误差分析表明这种行为源于化学因素。相比之下，在二甲基亚砜等极性非质子溶剂中对这种补偿行为的误差分析表明，这种相关性是由于范特霍夫分析中焓项和熵项之间固有相关性所固有的假象。在水等极性质子溶剂中的客体包封似乎是由客体的初始去溶剂化以及溶液中氢键网络的伴随重排驱动的。这种行为与水溶液中其他合成和天然的主客体及分子识别过程具有共同特征，从简单的冠醚到复杂的酶-配体相互作用。
