MESO-ARYL SUBSTITUTED METALLOPORPHYRINS SUPPORTED ON IMIDAZOLE PROPYL GEL (IPG) - CATALYTIC ACTIVITY IN THE OXIDATION OF CYCLOHEXANE AND CHARACTERIZATION OF IRON PORPHYRIN-IPG SYSTEMS

In this work, the catalytic activity of Fe and Mn porphyrins with meso-aryl electron withdrawing substituents in the hydroxylation of cyclohexane using iodosylbenzene as the oxygen donor were compared. The catalysts were used in three ways: in solution, supported on imidazole propyl gel (IPG) and supported on silica gel (SG). Mn-porphyrin-IPG systems are better catalysts: Mn(TDCPP)-IPG gives 67% of cyclohexanol yield, while the corresponding solution system gives 17%. With the Fe(TDCPP)-IPG system, there is a decrease in the catalytic activity (25%), when compared to the solution system. It was possible to understand, through UV-Vis and EPR spectra characterization, that an excess of imidazole in the iron(III) porphyrin-IPG systems promotes partial catalyst deactivation due to the bis-imidazolyl coordination and reduction to iron(II). If the imidazole/Fe(TDCPP) ratio decreases in the Fe(TDCPP)-IPG, the yield increases to 60%. It was possible to recycle Mn(TDCPP)-IPG, Fe(TDCPP)-IPG and Fe(TFPP)IPG up to 5 times without leaching of the supported catalyst, which results in very efficient systems with high turnovers.