Entasis through Hook-and-Loop Fastening in a Glycoligand with Cumulative Weak Forces Stabilizing CuI
Entasis through Hook-and-Loop Fastening in a Glycoligand with Cumulative Weak Forces Stabilizing CuI
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DOI：
10.1021/ja510259p
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发表时间：
2015-01-28
影响因子：
15
通讯作者：
Policar, Clotilde
中科院分区：
文献类型：
--
作者：
Garcia, Ludivine;Cisnetti, Federico;Policar, Clotilde
通过限制配位球几何构型来控制金属离子性质的想法是由Vallee和Williams提出的，他们提出了内吸的概念，这一概念通常被认为是与金属生物分子有关的。然而，控制金属中心几何形状的相互作用往往仍然难以捉摸。在本研究中，比较了以糖支架为中心的几何约束的糖配体与无约束的烷基链上的类似配体对铜离子--铜-II或铜-I的配位性质。与其开链类似物相比，以糖为中心的配体对铜-II配位更具预构性，铜-I氧化还原状态具有不同寻常的额外稳定性。这种对Cu-I的偏好被认为是因为几何约束有利于糖基化配体的优化折叠，从而使空间斥力最小化。换言之，Cu-Id(10)物种是由价壳电子对排斥(VSEPR)稳定的。这一想法被理论上的非共价相互作用(NCI)分析合理化。研究表明，弱力的累积效应可以产生有效的扣环，就像钩环扣扣一样，糖醇配体内的精细结构特征可以减少铜-I状态的排斥作用。这项研究强调，单糖平台是合适的配基骨架，在金属中心进行精细的几何控制，配基内有一个弱相互作用网络。糖配体的这种结构优势使它们对金属络合很有吸引力。
The idea of a possible control of metal ion properties by constraining the coordination sphere geometry was introduced by Vallee and Williams with the concept of entasis, which is frequently postulated to be at stake in metallobiomolecules. However, the interactions controlling the geometry at metal centers remain often elusive. In this study, the coordination properties toward copper ions-Cu-II or Cu-I-of a geometrically constrained glycoligand centered on a sugar scaffold were compared with those of an analogous ligand built on an unconstrained alkyl chain. The sugar-centered ligand was shown to be more preorganized for Cu-II coordination than its open-chain analogue, with an unusual additional stabilization of the Cu-I redox state. This preference for Cu-I was suggested to arise from geometric constraints favoring an optimized folding of the glycoligand minimizing steric repulsions. In other words, the Cu-I d(10) species is stabilized by valence shell electron pair repulsion (VSEPR). This idea was rationalized by a theoretical noncovalent interactions (NCI) analysis. The cumulative effects of weak forces were shown to create an efficient buckle as in a hook-and-loop fastener, and fine structural features within the glycoligand reduce repulsive interactions for the Cu-I state. This study emphasizes that monosaccharide platforms are appropriate ligand backbones for a delicate geometric control at the metal center, with a network of weak interactions within the ligand. This structuration availing in glycoligands makes them attractive for metallic entasis.