Search results for "MANGANESE"

Copper-, cobalt-, and manganese-containing 17-tungsto-2-germanates.

2009

The sandwich-type tungstogermanates [Cu(3)(H(2)O)(B-beta-GeW(9)O(33)(OH))(B-beta-GeW(8)O(30)(OH))](12-) (1), [Co(H(2)O)(2){Co(3)(B-beta-GeW(9)O(33)(OH))(B-beta-GeW(8)O(30)(OH))}(2)](22-) (2), and [Mn(H(2)O)(2){Mn(3)(H(2)O)(B-beta-GeW(9)O(33)(OH))(B-beta-GeW(8)O(30)(OH))}(2)](22-) (3) were synthesized and characterized by single-crystal X-ray diffraction, elemental analysis, thermogravimetric analysis, and infrared spectroscopy. Polyanion 1 is composed of two nonequivalent Keggin units, (B-beta-GeW(8)O(31)) and (B-beta-GeW(9)O(34)), linked to each other via three copper(II) ions in such a way that there is a plane of symmetry passing through both Ge atoms and the unique Cu atom, resulting in…

Synthesis and Comparative Catalytic Study of Zirconia-MnCO3or -Mn2O3for the Oxidation of Benzylic Alcohols

2016

Abstract We report on the synthesis of the zirconia–manganese carbonate ZrO x (x  %)–MnCO3 catalyst (where x=1–7) that, upon calcination at 500 °C, is converted to zirconia–manganese oxide ZrO x (x  %)–Mn2O3. We also present a comparative study of the catalytic performance of the both catalysts for the oxidation of benzylic alcohol to corresponding aldehydes by using molecular oxygen as the oxidizing agent. ZrO x (x  %)–MnCO3 was prepared through co‐precipitation by varying the amounts of Zr(NO3)4 (w/w %) in Mn(NO3)2. The morphology, composition, and crystallinity of the as‐synthesized product and the catalysts prepared upon calcination were studied by using scanning electron microscopy, tr…

Synthesis, crystal structure and magnetic properties of the dinuclear manganese(II) complexes [Mn2(bpym)3(NCX)4] (bpym = 2,2′-bipyrimidine; X = S, Se)

1997

Abstract The dinuclear manganese(II) compounds of formula [Mn2(bpym)3(NCX)4], where bpym = 2,2′-bipyrimidine and X = S(1) and Se(2), have been prepared and their crystal structures determined by X-ray diffraction methods. 1 and 2 are isostructural. They crystallize in the triclinic P 1 space group with Z = 1, γ ( Mo K α ) = 0.71073 A , T = 295 K and a = 9.141(2), b = 9.248(2), c = 11.733(2) A , α = 74.88(2), β = 80.29(2), γ = 61.03(2)°, V = 836.7(3) A 3 , D c = 1.621 g cm −3 , M r = 316.7, F(000) = 412, and μ( Mo K α) = 10.54 cm −1 for 1 and a = 9.244(2), b = 9.278(2) A , c = 11.887(2) A , α = 75.19(2), β = 80.83(2), γ = 61.54(2)°, V = 865.7(3) A 3 , D c = 1.926 g cm −3 , M r = 1004.3, F(00…

Pseudohalide derivatives of manganese(II) and copper(II) complexes with mepirizole, a biologically active pyrimidyl-pyrazole ligand

1989

Abstract The synthesis and characterization of thiocyanate and azide derivatives of mepirizole(4-methoxy-2-(5-methoxy-3-methyl-pyrazol-1-yl)-6-methylpyrimidine, hereinafter L) with manganese(II) and copper(II) is reported. The compounds were characterized by IR, electronic and EPR spectra and analytical data. Spectroscopic results suggest the existence of dimeric neutral entities [L2Cu2(μ-X)2(X)2] (X = NCS or N3) with unsymmetrical end-to-end bridges and five-coordination geometry around the copper(II) ion. Magnetic susceptibility data show that in the azide derivative the copper atoms are antiferromagnetically coupled (J = −18 cm−1), but no magnetic exchange interaction could be detected i…

Oral intake of cadmium, cobalt, copper, iron, lead, nickel, manganese and zinc in the university student's diet.

1993

A duplicate diet meal study was carried out with a group of university students living in a hostel, in order to estimate the intake of Zn, Cd, Co, Cu, Fe, Mn, Ni and Pb. Zn, Cu, Fe, Mn and Ni were determined by flame atomic absorption spectrophotometry and Cd, Co and Pb by graphite furnace atomic absorption spectrophotometry after a nitric acid wet digestion procedure. The estimated intake values from the contents of breakfast, lunch, dinner and drinks were compared with the values of the Provisional Tolerable Daily Intake (PTDI) in the case of Cd and Pb, Recommended Dietary Allowances (RDA) of Co, Fe and Zn and Estimated Safe and Adequate Dietetic Daily Intake (ESADDI) of Cu and Mn. Neithe…

Toxicity of manganese on embryos of the sea urchin, Paracentrotus lividus.

2008

2017

A hybrid bioinspired material with manganese(II) complexes grafted on the surface of a mesostructured porous silica is investigated. The Mn sites mimic the manganese-dependent dioxygenase (MndD), which is an enzyme that catalyses the oxidation of catechol derivatives. The metal complexes were introduced in the silica using a dinuclear complex [Mn2L2(Cl)2(μ-Cl)2] as a precursor with a clickable ligand N,N′-bis[(pyridin-2-yl)methyl]prop-2-yn-1-amine (L). Azide moieties covalently grafted on MCM-41 type mesoporous silica were utilised to anchor the manganese complex through Huisgen cycloaddition using CuBr(PPh3)3 as a catalyst. A second functional group – trimethylsilyl or pyridine—was grafted…

Mixed‐valence trinuclear manganese clusters : Influence of the electronic transfer on the magnetic properties

1990

The magnetic behavior of mixed‐valence trinuclear clusters d4‐d4‐d5 is discussed on the basis of a model which takes into account valence delocalization and Heisenberg exchange. This model considers the competing effect between the electronic transfer and the localization of the extra electron due to an asymmetry of the triangular entity. The magnetic properties of the mixed‐valence oxo‐centered Mn(II)‐Mn(III)‐Mn(III) complexes formulated as Mn3O(O2CR)6L3 (R=Me, L=pyridine) are discussed on the basis of the developed model, supporting a significant intramolecular electron transfer. A comparison of these results to those previously reported by assuming a valence‐trapped model is given. Carlo…

Manganese-dependent growth of Oenococci

2005

Abstract Oenococci are usually grown in complex media supplemented with tomato juice. The manganese concentration of tomato juice is about 10 µM, which shows a growth-stimulating effect. Unexpectedly, we found that high concentrations of manganese (34 mM) could replace tomato juice. At this concentration, far exceeding the concentration in growth media, several Oenococcus oeni strains yielded the same cell density as in the presence of tomato juice. The observed significant differences in the manganese dependence should also have an impact on the growth of oenococci in must and wine, where they are used as starter cultures for the removal of malic acid.

2016

AbstractDetermining the manganese concentration in shells of freshwater bivalves provides a unique way to obtain information about climate and environmental changes during time-intervals that pre-date instrumental data records. This approach, however, relies on a thorough understanding of how manganese is incorporated into the shell material –a point that remained controversial so far. Here we clarify this issue, using state-of-the-art X-ray absorption and X-ray emission spectroscopy in combination with band structure calculations. We verify that in the shells of all studied species manganese is incorporated as high-spin Mn2+, i.e. manganese always has the same valence as calcium. More impo…