Supramolecular Assemblies between Macrocyclic Porphyrin Hexamers and Star-Shaped Porphyrin Arrays†
journal contributionposted on 27.06.2001, 00:00 by Simona Rucareanu, Olivier Mongin, Anne Schuwey, Nicolas Hoyler, Albert Gossauer, Walter Amrein, Hans-Ulrich Hediger
The syntheses of eight new star-shaped D3-symmetric arrays in which three 15-(pyrid-4-yl)porphyrin subunits are attached to the 1, 3, and 5 positions of a benzene core through linkers consisting of collinear repetitive phenylethynyl units have been carried out using Pd(0)-catalyzed coupling reactions. By the same procedure, an analogous 10-(4-pyridin-yl)porphyrin hexamer in which all positions of the benzene core are substitued has been obtained. Likewise, the preparation of suitably sized cyclic porphyrin hexamers, in which all six or at least three alternate porphyrin rings are complexed with Zn(II) ions, is described in detail. In solution, such cyclic porphyrin hexamers form supramolecular assemblies with the star-shaped polyporphyrins in which the latter are held in the interior of the macrocycle through coordination of the apical pyridine rings with the Zn(II) ions. The suggested structures are supported by 1H NMR spectroscopic and MALDI-TOF mass spectrometric measurements. They agree with the high values of the binding constants of the corresponding supramolecules, which range between K = 1.1 × 1010 and 1.4 ×109 M-1.