Magnetic Resonance of Oxidized Metalloporphyrins

Two diastereomeric forms of the bischelated, edge-sharing bioctahedral molecule bis[bis(diethylphosphino)ethane]hexachloroditantalum

“…Received May 7,1987 The characterization of oxidized metalloporphyrins is of much current interest because they serve as model systems for many redox reactions of metalloporphyrin-containing enzymes. It is well-established that oxidation of a metalloporphyrin can be metal-centered or ligand-centered, the latter producing a cation radical.…”

Electrochemistry and spectroscopy of dicyanobis(phenanthroline)iron, tetracarbonyltetrakis(cyclopentadienyl)tetrairon and dicarbonylcyano(cyclopentadienyl)iron in an acidic molten salt

“…''This value was recorded vs. Ag wire and has been adjusted to correspond to the A1/A13+ couple in the MR = 2.0 melt reference. 6 Molar extinction coeffi- a very weak absorption band at 2072 cm"1. The single strong band suggests a trans structure with acceptor groups attached to both CN ligands.8 Judging from the moderate blue shift in the visible spectrum, the acceptor strength of this weak Lewis acid, Aw, is significantly lower than the Lewis acid designated as As in 6.21 The adduct formed when MR < 1.0 is indicated in 7.…”

“…Methylene chloride and chloroform were dried by standard methods.16 Aluminum trichloride and n-butylpyridinium chloride were prepared and purified according to established procedures. 6 The melts were prepared in a drybox under continuous N2 purge by slowly adding the ground A1C13 to the BPC contained in a beaker equipped with a magnetic stir bar. The rate of addition was such that the melt temperature never exceeded 60 °C.…”

“…An attractive feature of this molten salt is that the acidity can be altered by varying the ratio, AfR, of the two components, A1C13 and n-butylpyridinium chloride. 6 In the present investigation, we have utilized this molten salt for an electrochemical and spectroscopic study of three compounds, Fe(phen)2(CN)2,7•8 Cp4Fe4(CO)4,9 and CpFe(CO)2(CN)10 (phen = 1,10-phenanthroline, Cp = cyclopentadienyl), known to form simple ligand-bridged adducts with Lewis acids.1'1011 Evidence for adduct formation has been reported for amines12 and quiñones13 dissolved in the highly acidic melts, and the electrochemistry of some metal carbonyl complexes and metallocenes in this molten salt has been investigated.14, 15 The research described here focuses on inorganic complexes containing ligands that are highly sensitive to the Lewis acidity of their environment, thereby providing convenient spectroscopic probes into the donor-acceptor properties of these molten salts.…”

Cyclic Voltammetric and EPR Studies on the Oxidation Products of Vanadyl Mesoporphyrin

“…The oxidation products of transition-metal porphyrins have received considerable attention in recent years . A large number of techniques such as NMR, EPR, Mössbauer, X-ray crystallography, magnetic measurements, resonance Raman, and EXAFS have been used to characterize the structural features of these systems. − Many of the studies on the oxidation products, especially those of iron porphyrins, have been useful in tracing the mechanistic aspects of the functioning of heme enzymes . Some of the iron and manganese porphyrins have been used as catalysts in oxidation reactions. , We report in the present work some of our findings on the ESR and electrochemical behavior of the oxidation products of vanadyl mesoporphyrin dimethylester, VO(MESO).…”