近日，美国杜克大学教授Stephen L. Craig研究团队的研究发现二茂铁机械响应性聚合物远端构象锁定可以引导反应途径，从而提高机械化学反应性。 相关论文发表在2020年出版的《自然—化学》杂志上。

课题组使用单分子力学光谱揭示了一系列二茂铁的力学反应性与其在反应物中的环张力无关，但限于他们两个茂环配体的旋转重合时。远端附件可以用于将二茂铁解离机理限制在通过配体“剥离”，不同于更常见的对茂环父体的"剪断"机理，使得解离速率常数在~1nM外力下增加几个数量级。这也会改善宏观、多响应表现，包括在含二茂铁聚合物中的机械色变和力致交联。

研究人员表示，机械响应性聚合物可用于产生基于张力的在聚合材料中的共价化学响应，包括压力增强、压力感应和网络重建。通常来说，理想的机械响应性聚合物是在不存在外力时惰性，但在施加张力下具有高反应性。茂金属由于兼具未施加力的稳定性和外力下反应性，具有作为机械响应性聚合物的潜力，然而其反应性的力学基础仍未被研究。

附：英文原文

Title: Distal conformational locks on ferrocene mechanophores guide reaction pathways for increased mechanochemical reactivity

Author: Yudi Zhang, Zi Wang, Tatiana B. Kouznetsova, Ye Sha, Enhua Xu, Logan Shannahan, Muge Fermen-Coker, Yangju Lin, Chuanbing Tang, Stephen L. Craig

Issue&Volume: 2020-12-21

Abstract: 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 ~1nN. It also leads to improved macroscopic, multi-responsive behaviour, including mechanochromism and force-induced cross-linking in ferrocenophane-containing polymers.

DOI: 10.1038/s41557-020-00600-2

Source: https://www.nature.com/articles/s41557-020-00600-2