Rj. Balahura et Ra. Kirby, KINETICS AND MECHANISM OF THE REDUCTION OF MANGANESE PORPHYRINS - REACTION AT THE PERIPHERY OF THE PORPHYRIN RING, Inorganic chemistry, 33(6), 1994, pp. 1021-1025
The reduction of is(N-methyl-4-pyridinium)porphinato]manganese(III) an
d trakis(4-carboxyphenyl)-porphinato]manganese(III), Mn(III)TMPyP and
Mn(III)TCPP, by cobalt(II) sepulchrate and sodium dithionite has been
studied. The reduction of MnTMPyP by both reducing agents is strongly
dependent on the ionic strength of the medium, and the reduction with
Co(sep)2+ is also catalyzed by chloride ion. The kinetic data are cons
istent with attack of reducing agent at the periphery of the porphyrin
ring. For MnTCPP, the reduction by Co(sep)2+ is biphasic, indicating
two parallel reaction pathways-attack of Co(sep)2+ at the periphery of
the ring and at the axial waters. The data for the reaction of MnTCPP
with dithionite are consistent with rate-determining formation of a r
adical anion followed by rapid intramolecular reduction of manganese(I
II) to manganese(II).