Controllable Topological Transformations of 8 <sub>18</sub> Molecular Metalla‐knots by Oxidation of Thiazole‐Based Ligands
Hai‐Ning Zhang, Guo‐Xin Jin
Abstract
Abstract By exploiting coordination‐driven self‐assembly, high yields of two 8 18 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 ( L 1 ), 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 L 1 to N‐thiazole‐oxide‐based ligand 2‐(pyridin‐4‐yl)‐5‐(pyridin‐4‐ylethynyl)benzo[d]thiazole 3‐oxide ( L 2 ), which enabled the selective construction of the corresponding tetranuclear macrocycles. Notably, two molecular metalla‐knots could be topologically transformed from 8 18 knots to simple monocycles because the L 1 alkyne bond was inert toward m ‐CPBA, as confirmed by liquid‐state NMR spectroscopy, ESI‐TOF/MS, and elemental analysis.