Post-assembly Modification of Tetrazine-Edged Fe^II₄L₆ Tetrahedra

Post-assembly modification (PAM) is a powerful tool for the modular functionalization of self-assembled structures. We report a new family of tetrazine-edged FeII4L6 tetrahedral cages, prepared using different aniline subcomponents, which undergo rapid and efficient PAM by inverse electron-demand Diels–Alder (IEDDA) reactions. Remarkably, the electron-donating or -withdrawing ability of the para-substituent on the aniline moiety influences the IEDDA reactivity of the tetrazine ring 11 bonds away. This effect manifests as a linear free energy relationship, quantified using the Hammett equation, between σpara and the rate of the IEDDA reaction. The rate of PAM can thus be adjusted by varying the aniline subcomponent.组装后修饰（Post-assembly modification, PAM）是实现自组装结构模块化功能化的强有力工具。本文报道了一类全新的四嗪边缘FeII4L6四面体笼，该类笼状结构可通过不同苯胺亚组分制备得到，并可通过逆电子需求狄尔斯-阿尔德（Inverse electron-demand Diels–Alder, IEDDA）反应实现快速且高效的组装后修饰。值得注意的是，苯胺片段对位取代基的给电子或吸电子能力，可对间隔11个化学键的四嗪环的IEDDA反应活性产生调控作用。该效应表现为对位取代基常数σpara与IEDDA反应速率之间的线性自由能关系，可通过哈米特方程进行量化。由此，可通过调整苯胺亚组分的种类，实现组装后修饰反应速率的精准调控。