Controllable Topological Transformations of 8₁₈ Molecular Metalla‐knots by Oxidation of Thiazole‐Based Ligands

Abstract

By exploiting coordination‐driven self‐assembly, high yields of two 818 molecular metalla‐knots could be obtained using a thiazole‐moiety‐containing asymmetric dipyridyl ligand 2‐(pyridin‐4‐yl)‐5‐(pyridin‐4‐ylethynyl)benzo[d]thiazole (L1), as confirmed using X‐ray crystallographic analysis, electrospray ionization‐time‐of‐flight/mass spectrometry (ESI‐TOF/MS), and detailed liquid‐state nuclear magnetic resonance (NMR) spectroscopy. To modulate the self‐assembled structures, m‐chloroperbenzoic acid (m‐CPBA) was utilized to oxidize thiazole‐based ligand L1 to N‐thiazole‐oxide‐based ligand 2‐(pyridin‐4‐yl)‐5‐(pyridin‐4‐ylethynyl)benzo[d]thiazole 3‐oxide (L2), which enabled the selective construction of the corresponding tetranuclear macrocycles. Notably, two molecular metalla‐knots could be topologically transformed from 818 knots to simple monocycles because the L1 alkyne bond was inert toward m‐CPBA, as confirmed by liquid‐state NMR spectroscopy, ESI‐TOF/MS, and elemental analysis.