A [3]rotaxane composed of a zinc porphyrin tetra-substituted with coordinating macrocycles and of two short rigid axles

Abstract

The syntheses of a porphyrin bearing four peripheral rings and of the corresponding [3]rotaxane are reported. The porphyrinic tetra-macrocycle consists of four 1,10-phenanthroline-containing rings attached to the meso positions of a central zinc porphyrinvia single C–C bonds. The [3]rotaxane is composed of one central porphyrin and of two short rigid axles that contain two bidentate coordination sites and end with bulky stoppers. The rotaxane displays a novel architecture where each axle is threaded through two adjacent rings of the porphyrin. The free-base porphyrin was synthesised in 25% yield under optimised conditions. A microwave-enhanced procedure derived from the Adler–Rothemund method was developed for this condensation. The “gathering-and-threading” effect of copper(I) and subsequent stoppering by click chemistry were used to synthesise the [3]rotaxane in a two-step, one-pot reaction.