Self-assembly in water of the sodium salts of meso-sulfonatophenyl substituted porphyrins

Abstract

The aggregation in water of the free bases and the diprotonated forms of p-sulfonatophenyl and phenyl meso-substituted porphyrins [sodium salts of 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin (TPPS₄), 5,10,15-tris(4-sulfonatophenyl)-20-phenylporphyrin (TPPS₃), 5,10-bis(4-sulfonatophenyl)-15,20-diphenylporphyrin (TPPS_2A), 5,15-bis(4-sulfonatophenyl)-10,20-diphenylporphyrin (TPPS_2O), 5-(4-sulfonatophenyl)-10,15,20-diphenylporphyrin (TPPS₁) and 5,15-bis(4-sulfonatophenyl)porphine (DPPS_2O)] was studied by UV/Vis, ¹H-NMR, fluorescence, polarized fluorescence and resonance light scattering. The presence of hydrophobic phenyl groups favours the aggregation. The free bases TPPS₄ and TPPS₃ aggregate into stacks of ill-defined geometry. TPPS_2A and DPPS_2O give H-aggregates. TPPS_2O and TPPS₁ give J-aggregates through interaction of the hydrophobic phenyl groups, that is their geometry corresponds to edge-to-edge arrangements. All these porphyrins give J-aggregates upon diprotonation, through electrostatic interactions between the positively charged porphyrin ring and the sulfonato group. These J-aggregates give different arrays depending on the meso-substitution pattern.