Department of Chemistry, Zhejiang University, Hangzhou, 310027, PR China.
Key Laboratory of Excited-State Materials of Zhejiang Province, Zhejiang University, Hangzhou, 310027, PR China.
Nat Commun. 2022 Jun 21;13(1):3557. doi: 10.1038/s41467-022-31289-1.
The preparation of topologically nontrivial molecules is often assisted by covalent, supramolecular or coordinative templates that provide spatial pre-organization for all components. Herein, we report a trefoil knot that can be self-assembled efficiently in water without involving additional templates. The direct condensation of three equivalents of a tetraformyl precursor and six equivalents of a chiral diamine produces successfully a [3 + 6] trefoil knot whose intrinsic handedness is dictated by the stereochemical configuration of the diamine linkers. Contrary to the conventional wisdom that imine condensation is not amenable to use in water, the multivalent cooperativity between all the imine bonds within the framework makes this trefoil knot robust in the aqueous environment. Furthermore, the presence of water is proven to be essential for the trefoil knot formation. A topologically trivial macrocycle composed of two tetraformyl and four diamino building blocks is obtained when a similar reaction is performed in organic media, indicating that hydrophobic effect is a major driving force behind the scene.
拓扑非平凡分子的制备通常需要借助共价、超分子或配位模板来为所有组成部分提供空间预组织。在此，我们报道了一种三叶结，它可以在没有额外模板的情况下在水中高效自组装。三个当量的四醛前体和六个当量的手性二胺直接缩合成功地生成了一个[3+6]三叶结，其内在手性由手性二胺连接物的立体化学构型决定。与传统观点相反，亚胺缩合不适用于水相，该结构中所有亚胺键之间的多价协同作用使这种三叶结在水相环境中具有较强的稳定性。此外，证明水的存在对于三叶结的形成是必不可少的。当在有机介质中进行类似的反应时，得到了一个由两个四醛和四个二胺构筑块组成的拓扑平凡大环，表明疏水效应是背后的主要驱动力。
