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

Abstract

Post-assembly modification (PAM) is a powerful tool for the modular functionalization of self-assembled structures. We report a new family of tetrazine-edged Fe^II₄L₆ 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 <i>para</i>-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 σ_<i>para</i> and the rate of the IEDDA reaction. The rate of PAM can thus be adjusted by varying the aniline subcomponent