Electron Transfer Chemistry of Organometallic Porphyrins

烷基和芳基金属西格玛键合的卟啉的单电子氧化通常伴随着西格玛键合的有机配体的金属向氮气的迁移。本文结合电化学、UV-Vis和ESR光谱和停流动力学研究了(P)M(R)和(P)M(R)(L)型单氧化有机卟啉的反应和性质，其中P=取代卟啉的二阴离子：TPP或OEP，M=Co或Fe，R=n-Bu，Et，Me或Ph，L=乙腈或取代吡啶。我们的研究结果清楚地表明，在特定的溶液条件下可以生成(TPP)Co^&lt；IV&gt；(R)络合物，钴-碳键的断裂是通过R到Co的分子内电子转移来实现的，这导致了R基团的金属向氮的迁移。在类似的Mannar中，芳基西马键铁卟啉(OEP)Fe^&lt；III&gt；(R)的单电子氧化导致形成Fe^&lt；IV&gt；中心，该中心总是在迁移之前生成。

The one-electron oxidation of alkyl and aryl metal sigma-bonded porphyrins is often followed by a metal to nitrogen migration of the sigma-bonded organic ligand. Several studies of oxidized cobalt sigma-bonded porphyrins have suggested that a Co^<III> pi cation radical rather than a Co^<IV> cation is generated prior to the migration.The present study combines the use of electrochemistry, UV-vis and ESR spectroscopy and stopped flow kinetics to investigate the reactions and properties of singly oxidized organoporphyrins of the type (P) M (R) and (P) M (R)(L) where P = the dianion of substituted porphyrins : TPP or OEP,M = Co or Fe, R = n-Bu, Et, Me or Ph, L = acetonitrile or a substituted pyridine. The results of our studies show clearly that a (TPP) Co^<IV> (R) complex can be generated under specific solution conditions and the cleavage of the cobalt-carbon bond occurs via a rate-determining intramolecular electron transfer from R to Co and this results in a metal to nitrogen migration of the R group. In a similar mannar, one-electron oxidation of an aryl sigma-bonded iron porphyrin, (OEP) Fe^<III> (R) results in the formation of an Fe^<IV> center which is invariably generated prior to migration.