N-porphyrinylamino and -amido compounds by addition of an amino or amido nitrogen to a porphyrin meso position

This report describes the synthesis and characterization of a series of oct aethylporphyrin derivatives in which the porphyrin pi-network is connected to phenyl, 5-fluoranthenyl, or 1-pyrenyl aromatic systems through a meso am ino or amido nitrogen. Metal-free bases and zinc(II) and iron(III) complexe s have been obtained. These compounds represent the first examples of linka ges between porphyrins and extended pi-networks through a nitrogen atom dir ectly attached to a porphyrin meso position. H-1 NMR studies of the metal-f ree bases and zinc complexes showed that in the amido-linked adducts, the p lane containing the aryl substituent was oriented perpendicular to the plan e of the porphyrin. Linkage through the secondary amino nitrogen, however, allowed the aryl plane to rotate toward coplanarity with the porphyrin plan e, resulting in conjugation of the highest occupied aryl and porphyrin mole cular orbitals through the nitrogen lone pair. In developing routes to the amino-linked compounds, the facile formation of fused azaaryl chlorins via an oxidative intramolecular cycloaddition was observed. An aryl carbon orth o to the meso linkage attacked the beta-carbon of an adjacent pyrrole ring, accompanied by 1,2-migration of a pyrrole beta-ethyl substituent and a two -electron oxidation of the initially formed macrocycle. The resulting struc tures are analogous to benzochlorins. The electronic spectra of the metal-f ree bases are characterized by intense, long-wavelength bands in the visibl e region. Molecular structures of the chloroferric complexes of the azabenz ofluorantheno- and azabenzpyrenoporphyrin macrocycles (derived from fusion of the fluoranthenyl and pyrenyl substituents, respectively) were obtained by X-ray diffraction. The porphyrin moiety in the azabenzofluoranthenoporph yrin adopted a gable structure, with a 22 degrees fold along a diagonal inc luding the pyrrole-ring C4 and C16 alpha-carbons. By contrast, the azabenzp yrenoporphyrin was virtually planar.