Allosteric-controlled metal specificity of a ditopic ligand
Allosteric-controlled metal specificity of a ditopic ligand
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DOI：
10.1002/anie.200502571
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发表时间：
2005-01-01
影响因子：
16.6
通讯作者：
Whitehead, M
中科院分区：
文献类型：
--
作者：
Baylies, CJ;Riis-Johannessen, T;Whitehead, M
在金属超分子化学领域，有许多例子表明，精心设计的配体可以产生对某些金属离子具有选择性的物种。证明了含有三个联吡啶单元并通过脂肪或乙醚单元连接的两个配体的混合物在与铜离子和镍离子反应时分别只形成同核和同向三核双螺旋和三螺旋。[2]另一种提高金属专一性的方法是在配体链中引入离散的结合结构域，使每个结合结构域针对特定的金属离子。[3]然而，当使用后一种策略时，配体系统中包含的信息，即其“编程”，在合成阶段最终确定，此后不能改变。在这里，我们描述了一个同位配体L1，它对不同过渡金属离子的选择性可以通过将较大的S嵌段金属离子添加到冠醚部分而有效地重新编程。这种方法与Rebek等人展示的变构效应有关，在该效应中，冠醚对第1族金属离子的配位能力受到远程联吡啶配位结构域的影响。然而，在这种情况下，相反的情况发生，因为冠醚单元的配位控制了远程硝基单元作为四齿或双齿结构域的能力。其他可重编程系统已被证明控制螺旋结构的形成[5]并调节其节距长度。[6]L1(方案1)与等摩尔量的[Cu(MeCN)4]PF6在MeCN中反应得到暗红色溶液，ESI-MS分析表明，在m/z 1497处与{[Cu2(L1)2](PF6)}+形成了双核双螺旋结构。此外，冠醚部分
There are numerous examples in the field of metallosupramolecular chemistry that demonstrate that careful design of ligands can produce species that are selective to certain metal ions.[1] For example, Lehn et al. demonstrated that a mixture of two ligands that contain three bipyridine units and are linked either by aliphatic or ether units form only homonuclear and homoleptic trinuclear double and triple helicates upon reaction with Cu+ and Ni2+ ions, respectively.[2] Another approach to enhance metal specificity is to introduce discrete binding domains within a ligand strand such that each domain is specific to a particular metal ion.[3] However, when using the latter strategies, the information contained within the ligand system, that is, its “programming”, is finalized at the synthetic stage and cannot be altered thereafter. Herein, we describe a ditopic ligand L1, whose selectivity for different transition-metal ions can effectively be “reprogrammed” by the addition of the larger s-block-metal ions to the crown ether moiety. This approach is related to the allosteric effect demonstrated by Rebek et al., in which the ability of a crown ether to coordinate Group1 metal ions is influenced by coordination of a remote bipyridine coordination domain.[4] In this case, however, the reverse occurs as coordination of the crown ether unit controls the ability of a remote nitrogendonor unit to act as either a tetradentate or bisbidentate domain. Other reprogrammable systems have been shown to control the formation of helicates [5] and modulate their pitch length.[6]The reaction of L1 (Scheme 1) with an equimolar amount of [Cu (MeCN) 4] PF6 in MeCN gave a dark-red solution, and ESI-mass-spectrometric analysis showed the formation of a dinuclear double helicate with an ion at m/z 1497 consistent with {[Cu2 (L1) 2](PF6)}+. In addition, the crown ether moiety