Stepwise syntheses of meso-aryl-substituted porphyrins and related macrocycles

The rational synthesis of meso-aryl substituted porphyrins and related macrocycles were investigated and their chelation behavior studied. ^ 1. meso-Tetraarylporphyrins are one of the most studied synthetic porphyrins because of their various potential applications in medicinal and materials chemistry and biomimetics. The less studied 5,15-diphenylporphyrin (5,15-DPP) has found applications, for instance, in multi-porphyrin assemblies. The equally interesting and potentially useful cis-isomer to 5,15-DPP, 5,10-diphenylporphyrin (5,10-DPP) has not been described in the literature before. We have utilized the 2 + 2 methodology (condensation of two dipyrrolic units) to synthesize the novel compound 5,10-DPP. ^ 2. meso-Triarylcorroles have become known only recently as the serendipitous side products of a pyrrole-benzaldehyde condensation reaction. We developed a rational, stepwise synthetic methodology to prepare meso-triarylcorroles. The key step in this method is the preparation of a triaryltetrapyrrane intermediate, which then is oxidatively cyclized to form the desired corrole. This synthetic method is applicable to the synthesis of both A3-type meso-substituted corroles and of A2B-type meso-substituted corroles. ^ meso-Triarylcorroles reacted with silver(I) acetate and copper (II) acetate to form [meso-triarylcorrolato]Ag(III) and [meso-triarylcorrolato]Cu(III), respectively. The saddled structures of both complexes containing the metals in unusual oxidation states were established by NMR spectroscopy, mass spectrometry, X-ray crystallography and X-ray photoelectron spectroscopy. [meso-tritolylcorrolato]Cu(III) exhibited a spin equilibrium between the Cu(III) complex and the Cu(II) cation radical complex as observed by variable-temperature NMR spectroscopy. ^ 3. Expanded (macrocycles containing a more than 18π-electron system) and contracted (macrocycles containing less than 18π-electron system) porphyrins are interesting because they may extend the rich coordination chemistry of the porphyrin macrocycle. Rational approaches were developed toward the synthesis of one novel expanded porphyrin (a pyrazole/pyrrole [26π] expanded porphyrin hybrid system) and one imine-linked tripyrrolic contracted porphyrin. Although the target molecules could not be prepared, this work provided insights into the stepwise building of porphyrinic macrocycles.