Rigid, star-shaped D 3-symmetric arrays have been synthesized in which three porphyrin macrocycles are attached to the 1, 3, and 5 positions each of a benzene core through linkers consisting of collinear repetitive phenylethynyl units. Using the same methodology, a dendridic porphyrin hexamer having an external diameter of ca. 10 nm has been also obtained. By successive substitution of the three benzene positions, both a porphyrin trimer, the three linkers of which are of different length, and a starlike porphyrin, in which the complexed metal ions are different from each other, have been synthesized. The latter is the first example of a prochiral arrangement of metal ions in a D 3-symmetric ligand. To investigate their capability of forming ordered self-assembled monolayers on gold substrates, some of the porphyrin trimers and the dendritic porphyrin hexamer described in this work bear meta-thioanisole units at the apical positions. Analogously to similar multiporphyrin systems described in the literature, in which, however, the chromophores were arranged collinearly, the interaction between the chromophores of the multiporphyrin arrays described in this work is negligible, in the ground state, while effective energy transfer takes place in the singlet excited state.

The syntheses of eight new star-shaped D(3)-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 substituted 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 (1)H 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 x 10(10) and 1.4 x10(9) M(-1).

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ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.