Post-Synthetic Modification-Induced Structural Transformations of 413 and 814 Metalla-Links via Sequential Oxidation of Dibenzothiophene Moieties.

Abstract

Investigating stimulus-responsive structural transformations of complex mechanically interlocked molecules (MIMs) is key to better understanding the dynamic behaviors of biological macromolecules. Herein, we integrated oxidation-reactive dibenzothiophene moieties into organic frameworks, which self-assembled with binuclear half-sandwich organometallic clips of varying lengths, achieving selective construction of a linear [3]catenane (413 metalla-link) and an exceptionally rare closed four-link chain (CFLC, 814 metalla-link), the latter representing a synthetically challenging, highly interlocked topology. Topological transformation of the linear [3]catenane into a metalla-macrocycle was driven by substantial steric repulsion induced by bulky sulfone groups upon full oxidation with 3-chloroperoxybenzoic acid. By contrast, the CFLC exhibited remarkable topological stability against oxidative modifications, consistently preserving 814 link topology throughout the sequential oxidation process despite in situ structural transformations, yielding sulfoxide- and sulfone-containing CFLC derivatives. All nonoxidized and oxidized supramolecular assemblies were comprehensively characterized using single-crystal X-ray diffraction, high-resolution electrospray ionization mass spectrometry, and nuclear magnetic resonance spectroscopy. This work unveils a new pathway for postsynthetic modification of MIMs and provides critical insights into chemically driven transformations of complex, higher-order interlocked architectures, with significant potential to mimic nature's sophisticated, dynamic molecular systems.