Effect of coordination ability of axial ligands on the stability and catalytic activity of chloro(tetramesitylporphyrinato)manganese(III) and lifetime of Mn-oxo intermediate

• Relation between the coordination ability of axial ligands and reduction potential of Mn(III)/Mn(II).
• Relation between coordinating ability of axial ligands and stability of manganese porphyrins.
• Relation between coordinating ability of axial ligands and catalytic activity of manganese porphyrins.
• Relation between coordinating ability of axial ligands and lifetime of intermediate oxo-manganese species.

Some nitrogen donors, acetate and bromide ions were used as co-catalyst in the epoxidation reaction of cis-stilbene by meta-chloroperbenzoic acid catalyzed by chloro(tetramesitylporphyrinato)manganese(III). Cyclic voltammetry was used for comparison of coordination ability of these axial ligands. Stability of manganese porphyrin complex and lifetime of Mn-oxo intermediate species were compared using UV–vis spectroscopy in the presence of these axial ligands. It was shown that increasing coordination ability of these axial ligands has positive effects on the stability of the catalyst and also on the stability of Mn-oxo intermediate species but has a negative effect on the catalytic activity of the manganese porphyrin complex.

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