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The article discusses the use of [{Mn (super)IV (salpn)} (sub)2 (mu-O,mu-OCH (sub)3)](CF (sub)3 SO (sub)3) as a probe of protonation on the reactivity of [Mn (super)IV (mu-O)] (sub)2. Experiments have been conducted to demonstrate that methylation of an oxo bridge in a transition metal dimer is analogue for protonation. more...

The one-electron oxidation of tert-butyl hydroperoxide in acetonitrile chloride forms a MnIIIMnIV(2-OHsalpn)2+ cation. The dinuclear alkoxide-bridged manganese(III) complex is oxidized by organic peroxides by a catalase reaction. The reaction disproportionates hydrogen peroxide by cycling between MnsuperIIIsub2 and MnsuperIIsub2 oxidation states. This reaction will yield dioxygen and water due to the initial reduction of MnsuperIIIsub2 to MnsuperIIsub2 by hydrogen peroxide. The oxidation of MnsuperIIIsub2 complex requires the homolytic cleavage of the peroxy bond. more...

Computer simulation facilitates the study of a 16-line EPR signal, emitted from Mn catalase Lactobacillus plantarum, at three microwave frequencies when excited to the Mn(III)/Mn(IV) state. A computer program analyzes the disturbance of the Zeeman term to third order to compute the hyperfine splitting of the signal. The presence of catalase is crucial to H2O2 disproportionation. more...

The X-ray absorption spectra and EXAFS spectra of acetonitrile, dimethyl sulfoxide, pyridine and tetrahydrothiophene solavated copper(I) ions and the acetonitrile and dimethyl sulfoxide solvated copper(III) ions were measured in solution. The tetrakis(acetonitrile)copper(I) and tetrakis(pyridine)copper(I) ions showed similar structures in solid state solution and contained tetrahedrally coordinated copper(I). The Cu-N bond distances were identical for both species in solid and in solution. more...

ESI-MS, UV-vis, XAS, and EPR spectroscopy were used to follow the real-time concentration changes of oxone and Mn complex [[([H.sub.2]O)-(terpy)[Mn.sup.III][([mu]-O).sub.2][Mn.sup.IV](terpy)([H.sub.2]O)].sup.3.+] in catalytic [O.sub.2]-evolving solution of [[([H.sub.2]O)-(terpy)[Mn.sup.III][([mu]-O).sub.2][Mn.sup.IV](terpy)([H.sub.2]O)].sup.3.+] + oxone. A small amount of the mixed-valent M[n.sup.III/IV.sub.2] species [[([H.sub.2]O)-(terpy)[Mn.sup.III][([mu]-O).sub.2][Mn.sup.IV](terpy)([H.sub.2]O)].sup.3.+] was present in the catalytic solution and its concentration correlated with the rate of [O.sub.2] evolution, suggesting a direct role in the catalysis of [O.sub.2] evolution. more...

The structural and physicochemical properties of the manganese-corrolazine (Cz) complexes (TBP8Cz)Mn(super V) equivalent to O and (TBP8Cz)Mn(super III) (where TBP=p-tert-butylphenyl) are determined. The improved synthesis of manganese(III) and manganese(V)-oxo corrolazine complexes is accomplished. more...

Research has been conducted on trinuclear Mn (super)II/Mn (super)IV)/Mn (super)II complex. The authors report that XANES spectroscopy and X-ray crystallography distinguish the Mn (super)II (sub)2 Mn (super)IV valence isomer from Mn (super)III (sub)2 Mn (super)II formulation. more...

Tri L12C and Tri L16C are amphiphilic peptides composed of 30 amino acids with cysteine in either the 12 or 16 position of the sequence. The preference of Arsenic(As)(III) for trigonal-pyramidal geometry and thiol coordination is used to direct folding of the peptide to form three-helix bundles under all conditions studied. more...

[Mn2III/IV(μ-O)2(terpy)2(OH2)2](NO3)3 (1, where terpy = 2,2′:6′2″-terpyridine) + oxone (2KHSO5·KHSO4·K2SO4) provides a functional model system for the oxygen-evolving complex of photosystem II that is based on a structurally relevant Mn-(μ-O)2-Mn moiety (Limburg, J.; et al. J. Am. Chem. Soc. 2001, 123, 423-430). In this study, electron paramagnetic resonance, ultraviolet-visible spectroscopy, electrospray ionization mass spectrometry, X-ray absorption spectroscopy, and gas-phase stable isotope ratio mass spectrometry were utilized to identify the title compounds in the catalytic solution. We find that (a) O2 evolution does not proceed through heterogeneous catalysis by MnO2 or other decomposition products, that (b) o atoms from solvent water are incorporated into the evolved O2 to a significant extent but not into oxone, that (c) the Mn2III/IV title compound 1 is an active precatalyst in the catalytic cycle of O2 evolution with oxone, while the Mn2IV/IV oxidation state is not, and that (d) the isotope label incorporation in the evolved O2, together with points a-c above, is consistent with a mechanism involving competing reactions of oxone and water with a "MnV=O" intermediate in the OO bond-forming step. [ABSTRACT FROM AUTHOR] more...

The reaction of a series of thiolate-ligated iron(II) complexes [Fe(II)([15]aneN(4))(SC(6)H(5))]BF(4) (1), [Fe(II)([15]aneN(4))(SC(6)H(4)-p-Cl)]BF(4) (2), and [Fe(II)([15]aneN(4))(SC(6)H(4)-p-NO(2))]BF(4) (3) with alkylhydroperoxides at low temperature (-78 °C or -40 °C) leads to the metastable alkylperoxo-iron(III) species [Fe(III)([15]aneN(4))(SC(6)H(5))(OOtBu)]BF(4) (1a), [Fe(III)([15]aneN(4))(SC(6)H(4)-p-Cl)(OOtBu)]BF(4) (2a), and [Fe(III)([15]aneN(4))(SC(6)H(4)-p-NO(2))(OOtBu)]BF(4) (3a), respectively. X-ray absorption spectroscopy (XAS) studies were conducted on the Fe(III)-OOR complexes and their iron(II) precursors. The edge energy for the iron(II) complexes (∼7118 eV) shifts to higher energy upon oxidation by ROOH, and the resulting edge energies for the Fe(III)-OOR species range from 7121-7125 eV and correlate with the nature of the thiolate donor. Extended X-ray absorption fine structure (EXAFS) analysis of the iron(II) complexes 1-3 in CH(2)Cl(2) show that their solid state structures remain intact in solution. The EXAFS data on 1a-3a confirm their proposed structures as mononuclear, 6-coordinate Fe(III)-OOR complexes with 4N and 1S donors completing the coordination sphere. The Fe-O bond distances obtained from EXAFS for 1a-3a are 1.82-1.85 Å, significantly longer than other low-spin Fe(III)-OOR complexes. The Fe-O distances correlate with the nature of the thiolate donor, in agreement with the previous trends observed for ν(Fe-O) from resonance Raman (RR) spectroscopy, and supported by optimized geometries obtained from density functional theory (DFT) calculations. Reactivity and kinetic studies on 1a- 3a show an important influence of the thiolate donor. more...