PORPHOCYANINES - EXPANDED AROMATIC TETRAPYRROLIC MACROCYCLES

Porphocyanines are tetrapyrrolic macrocycles containing two dipyrromet hene units linked together by two C=N-C bridges. The syntheses of 2,3, 7,8,14,15,19,20-octaethylporphocyanine 5,17-diphenylporphocyanine, 2,3 ,7,8-tetraethyl-17-phenylporphocyanine and other meso-aryl and beta-al kyl, including a tetra-beta-propionate, derivatives and metal complexe s are described. The physical and chemical properties of porphocyanine s show them to be aromatic. The aromaticity is reflected in the large deshielding of the outer beta-protons and shielding of the inner pyrro lic protons in their NMR spectra. The optical spectra of these compoun ds exhibit Soret and Q bands similar to porphyrins but all significant ly bathochromically shifted. The ability of porphocyanines to act as c atalysts for the generation of singlet molecular oxygen was investigat ed using a cholesterol oxidation assay.