Molecular Composite Knots

Molecular composite knots have been prepared from transition metal-assembled precursors via a Glaser acetylenic coupling reaction. The templating metal is copper(I), and the coordinating fragments incorporated into the final structure are 1,10-phenanthroline-type chelates. The compounds are composite knots as opposed to prime knots such as the classical trefoil knot. By combining two tied open-chain fragments in a cyclodimerization reaction, the simplest composite knots are obtained as a mixture of two topological diastereomers. The minimum number of crossing points used to represent the molecules in a plane is six. Due to the complexity of the entangled precursors and to the several cyclization possibilities, the formation yield of composite knots is only modest (∼3%). On the other hand, the compound has been fully characterized by ES-MS (molecular weight, 4037.8) and by 1 H NMR spectroscopy, including 2D NMR (NOESY).