This study investigates the self-assembly kinetics of three structurally related sulfonato-phenylporphyrins, 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin (TPPSFormula: see text, 5,10,15-tris (4-sulfonatophenyl)-20-phenyl-porphyrin (TPPSFormula: see text and 5,15-bis(4-sulfonatophenyl)-10,20-phenyl-porphyrin (Formula: see text-TPPSFormula: see text into supramolecular J-aggregates in acidic aqueous solutions, using a series of inorganic acids. The aggregation process, followed by UV/Vis spectroscopy, monitoring the characteristic B-band disappearance (434 nm) and the sharp, red-shifted J-band appearance (490 nm), exhibits typical sigmoidal, autocatalytic kinetic profiles. Kinetic parameters derived from Pasternack’s model reveal that TPPS 4 and t-TPPS 2 aggregation rates adhere to the Hofmeister series for anions (SOFormula: see text ClFormula: see text BrFormula: see text NOFormula: see text ClOFormula: see text, correlating linearly with the anions’ structure-making/breaking abilities. Notably, Formula: see text-TPPS 2 kinetics are an order of magnitude faster than TPPS 4 . In contrast, TPPS 3 exhibits deviations from Hofmeister behavior together with smaller critical nucleus sizes, likely reflecting its distinct nano-ribbon morphology compared with the nano-tubes/stacked platelets structures formed by the other porphyrins. This work highlights how subtle molecular changes and the ionic environment tune macroscopic material properties via non-covalent interactions.
Zagami et al. (Tue,) studied this question.