Acid Dissociation constant of tetrakis(4-sulfonatophenyl)porphinzinc (II) in mixed aqueous organic solutions of methanol

Porphyrins are aromatic macrocyclic molecules with very significant role in bioscience. Various complexes of porphyrin derivatives containing iron, magnesium and cobalt metal ion occur naturally in living organisms such as for instance in heme proteins (myoglobin, hemoglobin and cytochrome), chlorophyll and vitamin B12. These metalloporhyrins carry out vital biological processes such as transport and storage of oxygen, photosynthesis and electron transfer in plant, animal and human. According to these vital importances, detailed knowledge about acid-base properties of metalloporhyrins is valuable. In this work the acid dissociation constants of tetrakis(4-sulfonatophenyl)porphinezinc(II) have been determined in various mixtures of water-methanol solvents to examine the solvent dependence on its acid-base properties equilibria..