Probing the Dynamics of Imine-based Pentafoil Knot and Pentameric Circular Helicate Assembly

We investigate the self-assembly dynamics of an imine-based pentafoil knot and related pentameric circular helicates, each derived from a common bis(formylpyridine)bipyridyl building block, iron(II) chloride and either monoamines or a diamine. The mixing of circular helicates derived from different amines led to complete exchange of the N-alkyl residues on the periphery of the metallo-supramolecular scaffolds over 4 days in DMSO at 60 °C. Under similar conditions, deuterium-labeled and non-labeled building blocks showed full dialdehyde building block exchange over 13 days for open circular helicates, but was much slower for the analogous closed-loop pentafoil knot (> 60 days). Although both knots and open circular helicates self-assemble under thermo-dynamic control given sufficiently long reaction times, this is significantly longer than the time taken to afford the maximum product yield (two days). Highly effective error correction occurs during the synthesis of imine-based pentafoil molecular knots and pentameric circular helicates despite, in practice, the systems not operating under full thermodynamic control.