Epoxidations catalyzed by an ionic manganese(III) porphyrin and characterization of manganese(V, IV)-oxo porphyrin complexes by UV–vis spectrophotometer in ionic liquid solution

An ionic metalloporphyrin of manganese tetrakis-(4-N-trimethylaminophenyl)porphyrin hexafluorophosphate ([MnIIITTMAPP][PF6]5, 1c), resided in the mixed ionic liquids (ILs) of [BzMIM]BF4 and [BMIM]BF4, proved to be an efficient and recyclable catalytic system for styrene (derivative) epoxidations without the involvement of the auxiliary axial ligands. The epoxidation rate in 1c–IL could be dramatically promoted by addition of water. In the built-up 1c–IL–H2O system, the active manganese(V)-oxo porphyrin intermediate (1d, 444 nm) was stabilized to facilitate its detection by a UV–vis spectrophotometer. And the formation of the μ-oxo Mn(IV) porphyrin dimer (1e, 416 nm) was completely suppressed due to the counteraction between 1c and the IL.

Graphical abstractThe compositions of an ionic manganese porphyrin (1c) resided in the ionic liquids were applied triply as the catalyst, the axial ligand, and the solvent for epoxidations of styrene (derivatives) with advantages of high efficiency, suppressed oxidation destruction of the porphyrin itself, and dramatically improved stability of the active Mn(V)-oxo porphyrin intermediate.Figure optionsDownload full-size imageDownload as PowerPoint slide