Solubilization of carboxyl derivatives of porphyrin molecules by micelles of cationic surfactants: Solubilization capacity and localization sites

The article is dedicated to the processes of solubilization of virtually insoluble carboxy-substituted tetraphenylporphyrin macrocycles by micelles of cationic surfactants (CTAB, CPC, and MTAB) to enhance their solubility in water. The influence of various structural parameters on the efficiency of the solubilization process is discussed, specifically the nature of the surfactant's polar group (trimethylammonium group, +N(CH3)3, and pyridinium group, +NC5H5), the length of the surfactant's hydrocarbon tail (−C16H31 and −C14H29), and the position of the functional group (–COOH) in the phenyl rings of 5,10,15,20-tetraphenylporphyrin. The ability of two carboxy-substituted porphyrin isomers to localize within the micelles of CTAB, CPC, and MTAB was determined using UV–visible, fluorescence, and 1H NMR spectroscopy, as well as dynamic light scattering. The data indicate that the hydrodynamic radii of empty surfactant micelles increase in the order: MTAB © 2025 Elsevier B.V.