Photochemical generation of manganese(IV)-oxo porphyrins by visible light photolysis of dimanganese(III) μ-oxo bis-porphyrins

•We report photochemical studies of bis-porphyrin-manganese(IV) μ-oxo dimers.•We report a new photochemical generation of the porphyrin-manganese(IV)-oxo species.•We present spectral evidence of manganese(II) species.•We propose a disproportionation mechanism for photolysis of dimanganese(IV) μ-oxo dimers.

Visible light photolysis of dimanganese(III) μ-oxo bis-porphyrins, [MnIII(Por)]2O, was studied in three porphyrin systems with different electronic structures. Direct conversion of manganese (III) μ-oxo dimers to manganese(IV)-oxo porphyrins plus manganese(III) products has been observed in benzene solution upon light irradiation. The spectral signature of MnIV(Por)(O) was further confirmed by production of the same species in the known experiment of the MnIII(Por)Cl with PhI(OAc)2. Continuous irradiation of dimanganese(III) μ-oxo bis-porphyrins in the presence of pyridine or triphenylphosphine gave rise to the formation of MnII(Por)(Py) or MnII(Por)(PPh3) which were stable to be detected. A photo-disproportionation mechanism similar to that for diiron(III) μ-oxo bis-porphyrins was proposed to explain above photochemical behaviors of the three dimanganese(III) μ-oxo bis-porphyrins.

Graphical abstractVisible light photolysis of bis-porphyrin-manganese(III) μ-oxo dimers gave porphyrin-manganese(II) and manganese(IV)-oxo species that can be directly observed.Figure optionsDownload full-size imageDownload as PowerPoint slide