Spectral study of mono-meso-(hydroxyphenyl)octamethylporphyrins

The behaviour of porphyrins [mono-meso-(2-hydroxyphenyl)octamethylporphyrin, mono-meso-(4-hydroxyphenyl)octamethylporphyrin and mono-meso-(3,4-dihydroxyphenyl)octamethylporphyrin] in basic solution is examined by UV-Visible and 1H NMR spectroscopy. The unusual nature of the spectra may be explained by the formation of porphomethene moieties in which the porphyrin chromophore is modified by interruption of the π-system. The porphyrins in bases are less susceptible to oxidation in contrast with meso-tetrakis-(4′-hydrooxyphenyl)porphyrins.