Synthesis of a molecular trefoil knot by folding and closing on an octahedral coordination template

Abstract

The advent of template-directed synthesis has provided access to a range of new interlocked molecular architectures. Although many syntheses of molecular catenanes and rotaxanes have been reported, molecular knots are a class of molecules with topologically non-planar graphs that are rather rare. Here we report a synthetic strategy for the preparation of a molecular trefoil knot from a flexible bipyridine oligomer and a zinc(II) octahedral coordination template. The oligomer folds into a stable open-knot conformation in the presence of the template, and trapping of this arrangement through esterification or ring-closing metathesis produces the closed-knot complex. Subsequent removal of the template from the metathesis product results in a molecular trefoil knot.