Meso and β-pyrrole sulfonated porphyrins obtained by sulfonation of 5,15-bis(phenyl)porphyrin

Abstract

The sulfonation of 5,15-bis(phenyl)porphyrin (DPP) in concentrated sulfuric acid results in substitution on the β-pyrrolic positions and the expected sulfonation on the para positions of the phenyl substituents. The sodium salt of 5,15-bis(4-sulfonatophenyl)porphyrin-2-sulfonic acid ( S 3 DPP ) was prepared in good yield, the sodium salts of 5,15-bis(4-sulfonatophenyl)porphyrin ( S 2 A DPP ), 5-phenyl-15-(4-sulfonatophenyl)porphyrin-2-sulfonic acid ( S 2 B DPP ) and 15-phenyl-5-(4-sulfonatophenyl)porphyrin ( S 1 A DPP ) were isolated, and 5,15-bis(phenyl)porphyrin-2-sulfonic acid ( S 1 B DPP ) was detected in a mixture with S 1 A DPP . The β-pyrrole sulfonato substituents are stable and their potential synthetic use is shown by the preparation of the trisodium salt of 10-bromo-5,15-bis(4-sulfonatophenyl)porphyrin-2-sulfonic acid ( BrS 3 DPP ) by NBS bromination of S 3 DPP . In a methanol/sulfuric acid mixture the sulfonation occurs on the meso positions, and the tetrasodium salt of 10,20-bis (4-sulfonatophenyl)porphyrin-5,15-disulfonic acid ( S 4 DPP ) was obtained.