Spectral and Spatial Characteristics of TPPS3 and TPPS4 Aggregates

TPPS molecules, because of their unique properties, could be used in biomedicine and application as organic semiconductors for nanometer-scale photovoltaic cells, artificial light harvesting systems, nonlinear optic materials. However, some properties of these photosensitizers are not so well known which makes their application more complicated. In this work a thorough investigation was made to discover spectral and spatial characteristics of $5,10,15,20$-tetrakis(4sulfonatophenyl)porphyrin (TPPS4) and tris(4-sulfonatophenyl)-20-phenylporphyrin (TPPS3). The presence of sulfo groups changes spectral and spatial characteristics of the porphyrin. Our research investigated TPPS4 and TPPS3 solutions at different concentrations and pH levels, aggregation process and determined $\mathrm{pK}_{\mathrm{a}}$ value of these porphyrins.