0000000000132268
AUTHOR
Ikuo Nakanishi
Base Control of Electron-Transfer Reactions of Manganese(III) Porphyrins
Homogeneous electron-transfer kinetics for the reduction of four different manganese(III) porphyrins using different reductants were examined in deaerated acetonitrile, and the resulting data were evaluated in light of the Marcus theory of electron transfer to determine electron-exchange rate constants between manganese(III) and manganese(II) porphyrins. The investigated compounds are represented as (P)MnCl, where P = the dianion of dodecaphenylporphyrin (DPPX; X = H20, Cl12H8, or F20) or tetraphenylporphyrin (TPP). The electron transfer from semiquinone radical anion derivatives to (P)MnIIICl leads to formation of the corresponding MnII complex, [(P)MnIICl]−. The electron-exchange rate con…
Decreased Electron Transfer Rates of Manganese Porphyrins with Conformational Distortion of the Macrocycle
Slow electron transfer to manganese(iii) porphyrins results when the macrocycle deviates from planarity. This was demonstrated by measuring the kinetics of homogeneous electron transfer from a series of semiquinone radical anions to synthetic manganese porphyrins (shown schematically; R1 =H, Cl, F; R2 =H, F). Three of the four porphyrins studied have nonplanar macrocycles. These results could have implications for the role of manganese in biological electron transfer processes.
Migration Reactivities of σ-Bonded Ligands of Organoiron and Organocobalt Porphyrins Depending on Different High Oxidation States
Migration reactivities of sigma-bonded organo-iron and -cobalt porphyrins were examined as a function of the compound oxidation state. Migration rates were determined for both the one-electron and two-electron oxidized species produced in the electron-transfer oxidation with different oxidants in acetonitrile at 298 K. The investigated compounds are represented as [(OETPP)Fe(R)](n)()(+), where n = 1 or 2, OETPP = the dianion of 2,3,7,8,12,13,17,18-octaethyl-5,10,15,20-tetraphenylporphyrin, and R = C(6)H(5), 3,5-C(6)F(2)H(3), or C(6)F(5), and as [(TPP)Co(R)](n)()(+), where n = 1 or 2, TPP = the dianion of 5,10,15,20-tetraphenylporphyrin, and R = CH(3) or C(6)H(5). The rapid two-electron oxid…
Reduzierte Geschwindigkeit des Elektronentransfers bei Mangan-Porphy- rinen mit verzerrter Konformation des Makrocyclus
Ein langsamer Elektronentransfer auf Mangan(III)-Porphyrine ist die Folge, wenn der Porphyrinmakrocyclus nicht planar ist. Dies konnte anhand kinetischer Messungen des homogenen Elektronentransfers von einer Reihe von Semichinon-Radikalanionen auf synthetische Manganporphyrine (siehe Formel, R1 = H, Cl, F; R2 = H, F) gezeigt werden. In drei der vier untersuchten Porphyrine ist der Makrocyclus nicht planar. Dieses Ergebnis konnte fur das Verstandnis der Rolle von Mangan in biologischen Elektronentransferprozessen wichtig sein.