J-aggregates of 5,10,15,20-tetrakis(4-sulfonatophenyl)-porphyrin. An overview of the supramolecular self-assembling mechanism

Under acidic conditions and at high ionic strength or in the presence of templating species, 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin (TPPS4) self-organizes into J-aggregates. In these species, the porphyrins align in a general edge-to-edge geometry, responsible for their peculiar optical properties. The self-assembling process is hierarchical, and the kinetics are strongly dependent on the mixing protocols. In the case of sigmoidal profiles, the kinetic data have been treated using a model proposed in the literature by R.F. Pasternack. Accordingly, an autocatalytic growth with the formation of an m-mer of porphyrin units is the rate-determining step (RDS) leading to the eventual J-aggregates whose size spans from nano- up to the micro-scale. The impact of different experimental parameters, together with inorganic counter-anions, and various cationic and anionic species (organic anions, metal ions, porphyrins, and metal complexes) will be reviewed.