One-pot synthesis of porphyrin-based [5]rotaxanes

A one-pot reaction is used to make a series of [5]rotaxanes. The protocol involves simultaneous threading-followed-by-stoppering to trap a macrocycle (dibenzo[24]crown-8, DB24C8) on an axle to form a mechanically interlocked molecule (MIM) – in this case a rotaxane – and the condensation of an aldehyde with a pyrrole to form a porphyrin precursor. For each [5]rotaxane, a different combination of recognition site and stoppering group was used; the protonation state of the [5]rotaxane can be used to generate different co-conformational states for each [5]rotaxane making these systems potential multi-state switches for further study in solution or the solid-state.