Chemical and theoretical studies of tautomerism in meso-aza- and meso-tetra-aza-porphyrins. Crystal structure of 5-aza-13,17-diethyl-2,3,7,8,12,18-hexamethylporphyrinatocobalt(II)

Abstract

Meso-azoporhyrins exist in the meso-imino tautomeric form. Attempts to trap or generate the meso-amino tautomer were unsuccessful. STO-3G and CNDO/2 calculations indicate the meso-imino tautomer to lie > 22 kcal mol^–1 below the meso-amino tautomer in both meso-monoaza- and meso-tetra-aza-porphyrins. The crystal structure of a meso-monoazaocta-alkylporphyrinatocobalt(II) complex is reported.