Binary ionic iron(III) porphyrin nanostructured materials with catalase-like activity

Abstract

Supramolecular structures were prepared in water by ionic self-assembly of oppositely charged iron(III) porphyrins and tested as a new class of catalase mimics. Iron(III) porphyrins carrying the positively charged groups, N-methyl-4-pyridinium (FeTMPyP), 4-pyridinium (FeTHPyP) and tetrafluoro-4-imidazoliumphenyl (FeTFHImP) were assembled with iron tetrakis(4-sulfonatophenyl)porphyrin (FeTSPP), at an optimized pH. The material with the best catalase activity (FeTHPyP:FeTSPP) showed 65-77 catalase units (U)/mg in the pH range 3.5-7.0, which was significantly higher than the 3 U/mg observed for the individual porphyrins. Analogous metal-free structures had no catalytic activity. Micro-scale structures with nanoscale features were observed by Scanning Electron Microscopy. Studies of the chemical composition of materials by X-ray Photoelectron Spectroscopy showed the formation of structures with a 1:1 ratio for (+):(‒) tectons. Characterization of particles in solution was carried out at different pH and before and after catalysis by UV-vis spectroscopy, Dynamic Light Scattering (measurement of hydrodynamic diameters) and Electrophoretic Light Scattering (measurement of zeta potentials).