Six-sided heptaporphyrin array: Towards a nano-sized cube

A strategy in preparing a family of hexameric porphyrin cubes based on the interplay of Sn(IV)-O and Ru(II)-N interactions is described. In this first iteration, we have prepared the heptamer [Sn-IV(TPyP).(4)(2)][Ru(CO)(TPP)](6) (4 = (E)-(3-(4-pyridyl)acrylate)) constituting a 5,10,15,20-tetra(4-pyridyl)porphyrin (TPyP) core and 5,10,15,20-tetraphenylporphyrin (TPP) faces and compared its formation by stepwise and "one-pot" strategies where up to nine components are assembled in a single step in a regiospecific manner. In one example, the heptamer is formed around the template [Sn-IV(TPyP).(4)(2)] bearing pyridine groups in which the nitrogens radiate octahedrally along each vertex. The ability to modulate the axial vertex through choice of pyridine is also demonstrated. H-1 NMR measurements on [Sn-IV(TPyP).(4)(2)][Ru(CO)(TPP)](6) indicate that the protons on the core template are extremely shielded as a result of the anisotropy of the peripheral porphyrin units. Various NMR techniques, including NOESY experiments, have been used to characterise the heptamer in solution.