Distal conformational locks on ferrocene mechanophores guide reaction pathways for increased mechanochemical reactivity
Distal conformational locks on ferrocene mechanophores guide reaction pathways for increased mechanochemical reactivity
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DOI：
10.1038/s41557-020-00600-2
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发表时间：
2020-12
期刊：
影响因子：
21.8
通讯作者：
Yudi Zhang;Zi Wang;T. Kouznetsova;Ye Sha;Enhua Xu;L. Shannahan;M. Fermen-Coker;Yangju Lin;Chuanbing Tang;S. Craig
中科院分区：
文献类型：
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作者：
Yudi Zhang;Zi Wang;T. Kouznetsova;Ye Sha;Enhua Xu;L. Shannahan;M. Fermen-Coker;Yangju Lin;Chuanbing Tang;S. Craig
力学分子可用于在聚合物材料中产生依赖应变的共价化学反应，包括应力增强、应力传感和网络重构。一般来说，机械团在无力时是惰性的，但在施加张力时是高度反应性的。茂金属化合物具有潜在的无力稳定性和力偶联反应性的组合，但这种反应性的机理基础在很大程度上仍未被探索。在这里，我们用单分子力谱证明了一系列二茂铁的机械反应性与反应物中的环应变无关，而与它们的两个环戊二烯配体的旋转排列程度有关。远端连接可以用来限制二茂铁的解离机制，使其通过配体的“剥离”进行，而不是母体的“剪切”机制，导致解离速率常数在~1 NN的力下增加几个数量级。它还改善了宏观的多响应行为，包括机械变色和含二茂铁聚合物的力诱导交联性。
Mechanophores can be used to produce strain-dependent covalent chemical responses in polymeric materials, including stress strengthening, stress sensing and network remodelling. In general, it is desirable for mechanophores to be inert in the absence of force but highly reactive under applied tension. Metallocenes possess potentially useful combinations of force-free stability and force-coupled reactivity, but the mechanistic basis of this reactivity remains largely unexplored. Here, we have used single-molecule force spectroscopy to show that the mechanical reactivities of a series of ferrocenophanes are not correlated with ring strain in the reactants, but with the extent of rotational alignment of their two cyclopentadienyl ligands. Distal attachments can be used to restrict the mechanism of ferrocene dissociation to proceed through ligand ‘peeling’, as opposed to the more conventional ’shearing’ mechanism of the parent ferrocene, leading the dissociation rate constant to increase by several orders of magnitude at forces of ~1 nN. It also leads to improved macroscopic, multi-responsive behaviour, including mechanochromism and force-induced cross-linking in ferrocenophane-containing polymers.