Seco-Porphyrazines: Synthetic, Structural, and Spectroscopic Investigations

Abstract

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.