The Conversion of Superoxide to Hydroperoxide on Cobalt(III) Depends on the Structural and Electronic Properties of Azole-Based Chelating Ligands.

Conversion from superoxide (O) to hydroperoxide (OOH) on the metal center of oxygenases and oxidases is recognized to be a key step to generating an active species for substrate oxidation. In this study, reactivity of cobalt(III)-superoxido complexes supported by facially-capping tridentate tris(3,5-dimethyl-4-X-pyrazolyl)hydroborate ([HB(pz)]; Tp) and bidentate bis(1-methyl-imidazolyl)methylborate ([B(Im)Me(Y)]; ) ligands toward H-atom donating reagent (2-hydroxy-2-azaadamantane; AZADOL) has been explored. The oxygenation of the cobalt(II) precursors give the corresponding cobalt(III)-superoxido complexes, and the following reaction with AZADOL yield the hydroperoxido species as has been characterized by spectroscopy (UV-vis, resonance Raman, EPR).

Dioxygen Activation and Mandelate Decarboxylation by Iron(II) Complexes of N4 Ligands: Evidence for Dioxygen-Derived Intermediates from Cobalt Analogues.

The isolation, characterization, and dioxygen reactivity of monomeric [(TPA)M(mandelate)] (M = Fe, ; Co, ) and dimeric [(BPMEN)M(μ-mandelate)] (M = Fe, ; Co, ) (TPA = tris(2-pyridylmethyl)amine and BPMEN = ,-dimethyl-,-bis(pyridin-2-yl-methyl)ethane-1,2-diamine) complexes are reported. The iron(II)- and cobalt(II)-mandelate complexes react with dioxygen to afford benzaldehyde and benzoic acid in a 1:1 ratio. In the reactions, one oxygen atom from dioxygen is incorporated into benzoic acid, but benzaldehyde does not derive any oxygen atom from dioxygen.

Controlled Regulation of the Nitrile Activation of a Peroxocobalt(III) Complex with Redox-Inactive Lewis Acidic Metals.

Redox-inactive metal ions play vital roles in biological O activation and oxidation reactions of various substrates. Recently, we showed a distinct reactivity of a peroxocobalt(III) complex bearing a tetradentate macrocyclic ligand, [Co(TBDAP)(O)] () (TBDAP = ,'-di--butyl-2,11-diaza[3.3](2,6)pyridinophane), toward nitriles that afforded a series of hydroximatocobalt(III) complexes, [Co(TBDAP)(R-C(═NO)O)] (R = Me (), Et, and Ph).

Effect of the Electron Density of the Heme Fe Atom on the Nature of Fe-O Bonding in Oxy Myoglobin.

Mössbauer spectroscopy has been used to characterize oxygenated myoglobins (oxy Mbs) reconstituted with native and chemically modified Fe-enriched heme cofactors with different electron densities of the heme Fe atom (ρ) and to elucidate the effect of a change in the ρ on the nature of the bond between heme Fe and oxygen (O), i.e., the Fe-O bond, in the protein.

Redox-Inactive Metal Ions That Enhance the Nucleophilic Reactivity of an Alkylperoxocopper(II) Complex.

The importance of redox-inactive metal ions in modulating the reactivity of redox-active biological systems is a subject of great current interest. In this work, the effect of redox-inactive metal ions (M = Sc, Y, Yb, La) on the nucleophilic reactivity of a mononuclear ligand-based alkylperoxocopper(II) complex, [Cu(Pr-tren-C(CH)O)] (), was examined. was prepared by the addition of hydrogen peroxide and triethylamine to the solution of [Cu(Pr-tren)(CHCN)] (Pr-tren = tris[2-(isopropylamino)ethyl]amine) via the formation of [Cu(Pr-tren)(OH)] () in methanol (CHOH) at 30 °C.

A staged approach with initial tumor thrombectomy followed by hepatectomy for icteric-type hepatocellular carcinoma: A case report.

Introduction: Biliary drainage for patients with icteric-type hepatocellular carcinoma (HCC) is sometimes difficult, because the drainage tube makes contact with the tumor thrombus (TT) and effective drainage cannot be achieved due to hemobilia.

Presentation Of Case: We performed endoscopic naso-biliary drainage for an icteric-type HCC patient; however, the serum bilirubin level was not decreased due to bleeding from the TT. Therefore, we performed tumor thrombectomy in the bile duct and transection of the right hepatic bile duct prior to right hepatectomy.

Dinitrogen-Molybdenum Complex Induces Dinitrogen Cleavage by One-Electron Oxidation.

Reported here is the N cleavage of a one-electron oxidation reaction using trans-[Mo(depe) (N ) ] (1) (depe=Et PCH CH PEt ), which is a classical molybdenum(0)-dinitrogen complex supported by two bidentate phosphine ligands. The molybdenum(IV) terminal nitride complex [Mo(depe) N][BArf ] (2) (BArf =B(3,5-(CF ) C H ) ) is synthesized by the one-electron oxidation of 1 upon addition of a mild oxidant, [Cp Fe][BArf ] (Cp=C H ), and proceeds by N cleavage from a Mo -N=N-Mo structure. In addition, the electrochemical oxidation reaction for 1 also cleaved the N ligand to give 2.

Characterization and Reactivity of a Tetrahedral Copper(II) Alkylperoxido Complex.

A tetrahedral Cu alkylperoxido complex [Cu (TMG tach)(OOCm)] (1 ) (TMG tach={2,2',2''-[(1s,3s,5s)-cyclohexane-1,3,5-triyl]tris-(1,1,3,3-tetramethyl guanidine)}, OOCm=cumyl peroxide) is prepared and characterized by UV/Vis, cold-spray ionization mass spectroscopy (CSI-MS), resonance Raman, and EPR spectroscopic methods. Product analysis of the self-decomposition reaction of 1 in acetonitrile (MeCN) indicates that the reaction involves O-O bond homolytic cleavage of the peroxide moiety with concomitant C-H bond activation of the solvent molecule. When an external substrate such as 1,4-cyclohexadiene (CHD) is added, the O-O bond homolysis leads to C-H activation of the substrate.

Copper amine oxidases catalyze the oxidative deamination and hydrolysis of cyclic imines.

Although cyclic imines are present in various bioactive secondary metabolites, their degradative metabolism remains unknown. Here, we report that copper amine oxidases, which are important in metabolism of primary amines, catalyze a cyclic imine cleavage reaction. We isolate a microorganism (Arthrobacter sp.

New assay method based on Raman spectroscopy for enzymes reacting with gaseous substrates.

Enzyme activity is typically assayed by quantitatively measuring the initial and final concentrations of the substrates and/or products over a defined time period. For enzymatic reactions involving gaseous substrates, the substrate concentrations can be estimated either directly by gas chromatography or mass spectrometry, or indirectly by absorption spectroscopy, if the catalytic reactions involve electron transfer with electron mediators that exhibit redox-dependent spectral changes. We have developed a new assay system for measuring the time course of enzymatic reactions involving gaseous substrates based on Raman spectroscopy.

A Nuclear Resonance Vibrational Spectroscopic Study of Oxy Myoglobins Reconstituted with Chemically Modified Heme Cofactors: Insights into the Fe-O Bonding and Internal Dynamics of the Protein.

The molecular mechanism of O binding to hemoglobin (Hb) and myoglobin (Mb) is a long-standing issue in the field of bioinorganic and biophysical chemistry. The nature of Fe-O bond in oxy Hb and Mb had been extensively investigated by resonance Raman spectroscopy, which assigned the Fe-O stretching bands at ∼570 cm. However, resonance Raman assignment of the vibrational mode had been elusive due to the spectroscopic selection rule and to the limited information available about the ground-state molecular structure.

Structure and Reactivity of a Mononuclear Nonheme Manganese(III)-Iodosylarene Complex.

Transition metal-iodosylarene complexes have been proposed to be key intermediates in the catalytic cycles of metal catalysts with iodosylarene. We report the first X-ray crystal structure and spectroscopic characterization of a mononuclear nonheme manganese(III)-iodosylarene complex with a tetradentate macrocyclic ligand, [Mn(TBDAP)(OIPh)(OH)] (2). The manganese(III)-iodosylarene complex is capable of conducting various oxidation reactions with organic substrates, such as C-H bond activation, sulfoxidation and epoxidation.

A Manganese(V)-Oxo Tetraamido Macrocyclic Ligand (TAML) Cation Radical Complex: Synthesis, Characterization, and Reactivity Studies.

A mononuclear manganese(V)-oxo complex with tetraamido macrocyclic ligand (TAML), [Mn (O)(TAML)] (1), is a sluggish oxidant in oxidation reactions. Herein, a mononuclear manganese(V)-oxo TAML cation radical complex, [Mn (O)(TAML )] (2), is reported. It was synthesized by reacting [Mn (TAML)] with 3.

Dinitrogen Fixation by Vanadium Complexes with a Triamidoamine Ligand.

Dinitrogen-divanadium complexes with triamidoamine ligands, 1-3, were synthesized and characterized by resonance Raman, UV-vis, and NMR spectroscopy and elemental and X-ray structure analyses. X-ray structure analyses reveal that all three of the complexes have a dimeric structure with a μ-N ligand (N-N bond length 1.200-1.

N activation on a molybdenum-titanium-sulfur cluster.

The FeMo-cofactor of nitrogenase, a metal-sulfur cluster that contains eight transition metals, promotes the conversion of dinitrogen into ammonia when stored in the protein. Although various metal-sulfur clusters have been synthesized over the past decades, their use in the activation of N has remained challenging, and even the FeMo-cofactor extracted from nitrogenase is not able to reduce N. Herein, we report the activation of N by a metal-sulfur cluster that contains molybdenum and titanium.

Mn(III)-Iodosylarene Porphyrins as an Active Oxidant in Oxidation Reactions: Synthesis, Characterization, and Reactivity Studies.

Mn(III)-iodosylarene porphyrin adducts, [Mn(III)(ArIO)(Porp)], were synthesized by reacting electron-deficient Mn(III) porphyrin complexes with iodosylarene (ArIO) at -60 °C and characterized using various spectroscopic methods. The [Mn(III)(ArIO)(Porp)] species were then investigated in the epoxidation of olefins under stoichiometric conditions. In the epoxidation of olefins by the Mn(III)-iodosylarene porphyrin species, epoxide was formed as the sole product with high chemoselectivities and stereoselectivities.

Feasibility study of postoperative adjuvant chemotherapy with S-1 in patients with biliary tract cancer.

Background: The role of adjuvant chemotherapy has not yet been established for patients with resected biliary tract cancer. S-1 has been shown to exert activity against advanced biliary tract cancer. Therefore, we evaluated the feasibility of adjuvant chemotherapy with S-1 in patients with resected biliary tract cancer.

A Bis(μ-oxido)dinickel(III) Complex with a Triplet Ground State.

A bis(μ-oxido)dinickel(III) complex was synthesized and characterized by single crystal X-ray diffraction, resonance Raman, and ESI-mass measurements. Magnetic susceptibility measurements by SQUID and EPR spectroscopy reveal that the complex has a triplet ground state, which is unprecedented for high-valent metal (M) complexes with [M (μ-O) ] diamond core. DFT studies indicate ferromagnetic coupling of the nickel(III) centers.

A water-soluble supramolecular complex that mimics the heme/copper hetero-binuclear site of cytochrome oxidase.

In mitochondria, cytochrome oxidase (CO) catalyses the reduction of oxygen (O) to water by using a heme/copper hetero-binuclear active site. Here we report a highly efficient supramolecular approach for the construction of a water-soluble biomimetic model for the active site of CO. A tridentate copper(ii) complex was fixed onto 5,10,15,20-tetrakis(4-sulfonatophenyl)porphinatoiron(iii) (FeTPPS) through supramolecular complexation between FeTPPS and a per--methylated β-cyclodextrin dimer linked by a (2,2':6',2''-terpyridyl)copper(ii) complex (CuTerpyCD).

Dioxygen Activation and O-O Bond Formation Reactions by Manganese Corroles.

Activation of dioxygen (O) in enzymatic and biomimetic reactions has been intensively investigated over the past several decades. More recently, O-O bond formation, which is the reverse of the O-activation reaction, has been the focus of current research. Herein, we report the O-activation and O-O bond formation reactions by manganese corrole complexes.

Achieving One-Electron Oxidation of a Mononuclear Nonheme Iron(V)-Imido Complex.

A mononuclear nonheme iron(V)-imido complex bearing a tetraamido macrocyclic ligand (TAML), [Fe(NTs)(TAML)] (1), was oxidized by one-electron oxidants, affording formation of an iron(V)-imido TAML cation radical species, [Fe(NTs)(TAML)] (2); 2 is a diamagnetic (S = 0) complex, resulting from the antiferromagnetic coupling of the low-spin iron(V) ion (S = 1/2) with the one-electron oxidized ligand (TAML). 2 is a competent oxidant in C-H bond functionalization and nitrene transfer reaction, showing that the reactivity of 2 is greater than that of 1.

Distinct Reactivity of a Mononuclear Peroxocobalt(III) Species toward Activation of Nitriles.

A mononuclear side-on peroxocobalt(III) complex with a tetradentate macrocyclic ligand, [Co(TBDAP)(O)] (1), shows a novel and facile mode of dioxygenase-like reactivity with nitriles (R-C≡N; R = Me, Et, and Ph) to produce the corresponding mononuclear hydroximatocobalt(III) complexes, [Co(TBDAP)(R-C(═NO)O)], in which the nitrile moiety is oxidized by two oxygen atoms of the peroxo group. The overall reaction proceeds in one-pot under ambient conditions (ca. 1 h, 40 °C).

New mechanistic insights into intramolecular aromatic ligand hydroxylation and benzyl alcohol oxidation initiated by the well-defined (μ-peroxo)diiron(iii) complex.

A (μ-peroxo)diiron(iii) complex [Fe(L)(O)(PhCCO)] (1-O) with a dinucleating ligand (L), generated from the reaction of a carboxylate bridged diiron(ii) complex [Fe(L)(PhCCO)] (1) with dioxygen in CHCl, provides a diiron(iv)-oxo species as an active oxidant which is involved in either aromatic ligand hydroxylation or benzyl alcohol oxidation.

A Mononuclear Nonheme Iron(V)-Imido Complex.

Mononuclear nonheme iron(V)-oxo complexes have been reported previously. Herein, we report the first example of a mononuclear nonheme iron(V)-imido complex bearing a tetraamido macrocyclic ligand (TAML), [(TAML)Fe(NTs)] (1). The spectroscopic characterization of 1 revealed an S = 1/2 Fe(V) oxidation state, an Fe-N bond length of 1.

Synthesis and reactivity of a mononuclear non-haem cobalt(IV)-oxo complex.

Terminal cobalt(IV)-oxo (Co-O) species have been implicated as key intermediates in various cobalt-mediated oxidation reactions. Herein we report the photocatalytic generation of a mononuclear non-haem [(13-TMC)Co(O)] (2) by irradiating [Co(13-TMC)(CFSO)] (1) in the presence of [Ru(bpy)], NaSO, and water as an oxygen source. The intermediate 2 was also obtained by reacting 1 with an artificial oxidant (that is, iodosylbenzene) and characterized by various spectroscopic techniques.