Iron(III)-tetra-o-ureaphenylporphyrinosilica obtained by a sol–gel process: a study of EPR, surface area and catalytic activity

Abstract The properties, morphology and catalytic activity of an iron(III)-tetra-o-ureaphenylporphyrinosilica (FePS), obtained using two nitrogenous bases as catalysts in the sol–gel process, are reported. Electron paramagnetic resonance spectra have components due to FeIII high spin, a component at g∼4.3 due to porphyrins species in rhombic symmetry and a component in the region of 0.2 to 0.3 T attributed to Fe–Fe coupling. The solid samples have surface areas 645 and 723 cm2/g, the adsorption isotherms of the solids are type II and the hysteresis loop is type H1. The solids have porosity classified between meso- and macro- porous containing pores with regular morphology and cylindrical and/or polyhedral geometry. Scanning electron microscopy detects an amorphous material composed of aggregates and granules. The matrix effect on the catalytic activity of the FePS, in the Z-cyclooctene oxidation, using iodosylbenzene (PhIO) as oxygen donor was verified. In the repeat-use experiment with FeP:PhIO molar ratio of 1:2000, the total turnover number was 670 for FePS-py, while for the corresponding homogeneous system it was 342.