Studies on the effects of metal ions and counter anions on the aggregate behaviors of meso-tetrakis(p-sulfonatophenyl)porphyrin by absorption and fluorescence spectroscopy

The aggregation behaviors of meso-tetrakis(p-sulfonatophenyl)porphyrin (TPPS) in the function of metal ions and their counter anions (Cl−, SO42−, and NO3−) were investigated by absorption, fluorescence spectroscopy and resonance scattering spectrum. It was shown that the TPPS J-aggregates could be effectively promoted by metal ions under lower ionic strength. Moreover, the prominent effects of counter ions (Cl−, SO42−, and NO3−) on TPPS J- and/or H-aggregate formation at higher ionic strength were observed. These results suggested that the counter anions play a significant role in the formation of TPPS J- and/or H-aggregates and their conversion each other. Very interestingly, the absorption spectrum of metal ions investigated except for Co2+ leaves a WINDOW from ca. 450 to 550 nm centered at 490 nm in which the absorption of Cu2+ or Ni2+ ions per se was very weak. The spectrum window might be really significant in avoiding possible spectrum interferences when porphyrins are chosen as spectrometric reagents for the determination of metal ions based on J-aggregation.