A detailed description of the most important factors that influence synthetic iron porphyrin electron transfer reactions at electrodes is reported. Quantitative relationships that describe (1) the standard potential in terms of the porphyrin ring structure; (2) axial coordination of the central metal ion by nitrogenous bases, monovalent counterions, and diatomic ligands; and (3) the solvent in which the electron transfer is studied are presented. Combinations of these factors can be utilized to plan the synthesis of the appropriate iron porphyrin that will possess the desired standard potential (E°), the desired number of electrons in the redox reaction, as well as the desired ultimate reaction site (whether metal centered or porphyrin ring centered).
Abstract The kinetics of the reactions of (I) (and 6 other phenyl‐substituted analogues), (II) and (III) with trifluoroacetic anhydride and of (II) with trifluoro‐, trichloro‐, dichloro‐, monochloro‐ and unsubstituted acetic anhyride to form the corresponding nitrenoid Mn porphyrin complex are determined under pseudo‐first‐order conditions.
Abstract Oxidations of the title compounds (III) and (IV) are performed to study further the "ethyl" effect, that is, the abolition of carcinogenic activity when certain otherwise carcinogenic polynuclear aromatic hydrocarbons are substituted at the meso position by an ethyl group.
The X-ray structural determination is reported for the first compound possessing a single carbon atom bridging tow first-row transition metals with a linear Fe–C–Fe bond and an Fe–C bond length of only 1.675 Å.
The utility of electrochemistry as a tool for studying physical properties of metalloporphyrins has been recognized extensively during the last several years (1,2). It is now well known that the half wave potentials for metalloporphyrin electrooxidation-reduction are directly influenced by the number and type of complexed axial ligands and that these may, in some instances, be related to the dioxygen carrying ability of the M(II) metalloporphyrin where M is Co(3-6), Fe (7-9) or Mn (10). Enthalpy and entropy values for complexation of cobalt(II) (4,11,12) and iron(II) (13) porphyrins, by several Lewis bases have been reported, but similar data for Lewis base complexation is not available for the oxidized cobalt(III) and iron(III) species. This data is of some interest in that changes of solvation and/or ligand binding, concomitant with electron transfer, may produce large entropie effects which would significantly shift the half wave potentials as a function of temperature and could
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