Synthesis and characterization of a water-soluble porphyrin with a cyclic sulfone

Water-soluble sulfonated tetraarylporphyrins are studied in a wide variety of contexts including as analytical reagents and as possible agents in cancer photodynamic therapy as well as in antiviral and antidiabetic applications. Herein, we report the first synthesis of a pentasulfonated porphyrin bearing an internal cyclic sulfone ring. Treatment of 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin (TPPS4) with fuming H2SO4 gave a structure consistent with initial sulfonation followed by dehydration to give a sulfone bridge between an ortho-position of one of the phenyl groups and a β-pyrrole position on the porphine ring (TPPS4Sc). The structure was established by electrospray mass spectrometry and 1H NMR. The Soret UV–visible absorption is red shifted by about 32 nm compared to that of TPPS4.