Seco-Porphyrazines: Synthetic, Structural, and Spectroscopic Investigations

Linstead macrocyclization of dinitrile 1 gave [octakis(dimethylamino)porphyrazinato]magnesium(II) 2 and the seco-porphyrazine 4 from adventitious oxidation. The structure of the latter has been unequivocally established by an X-ray crystallographic study. Alternatively, compound 4 was obtained in high yield from the manganese dioxide-mediated oxidation of the free base porphyrazine 3 . This convenient method was further extended to core metalated and unsymmetrical porphyrazines. In crystals of zinc−seco-porphyrazine 11, the molecules exist as face-to-face dimers linked via complexation of the zinc center in one molecule to one of the amide oxygen atoms in the other and vice versa . The cleaved pyrrole ring in seco- and diseco-porphyrazines causes a ∼50−70 nm red-shifted split Q-band in the electronic absorption spectra.