Resonance Raman spectroscopy and density functional theoretical calculations of manganese corroles. A parallelism between high-valent metallocorroles and metalloporphyrins, relevant to horseradish peroxidase and chloroperoxidase compound I and II intermediates

Abstract

Soret-excited resonance Raman (RR) spectra are reported for the Mn(III) and Mn(IV)Cl derivatives of meso-tris(p-(trifluoromethyl)phenyl)corrole, H(3)T(p-CF(3)-P)Cor, and the Mn(III) derivative of beta-octabromo-meso-tris(p-(trifluoromethyl)phenyl)corrole, H(3)Br(8)T(p-CF(3)-P)Cor. Three high-frequency bands in the RR spectrum of Mn(III)[T(p-CF(3)-P)Cor] at 1465, 1524 and 1615 cm(-1) appear to upshift to 1486, 1528 and 1620 cm(-1) for Mn(IV)[T(p-CF(3)-P)Cor]Cl. This suggests that the electronic character of the corrole ligand is significantly different for these two compounds, which is consistent with electrochemical evidence for partial radical character of the corrole ligand for Mn(IV)[T(p-CF(3)-P)Cor]Cl but not for Mn(III)[T(p-CF(3)-P)Cor]. The observed upshifts are also consistent with DFT calculations showing a shortening of some of the relevant bonds in the Mn(IV)Cl derivative relative to the Mn(III) derivative. The results raise the possibility of an extensive parallelism between the electronic structures of high-valent metallocorroles and metalloporphyrins. Three high-frequency bands in the RR spectrum of Mn(III)[T(p-CF(3)-P)Cor] at 1331, 1465 and 1545 cm(-1) appear to downshift to 1320, 1457 and 1537 cm(-1) for Mn(III)[Br(8)T(p-CF(3)-P)Cor]. This is consistent with the suspected longer carbon-carbon bond lengths in the brominated corrole macrocycle.