- Rapid room-Temperature synthesis of ultrasmall cubic Mg-Mn spinel cathode materials for rechargeable Mg-ion batteries
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Reducing the particle size of cathode materials is effective to improve the rate capability of Mg-ion batteries. In this study, ultrasmall cubic Mg-Mn spinel oxide nanoparticles approximately 5 nm in size were successfully synthesized via an alcohol reduction process within 30 min at room temperature. Though the particles aggregated to form large secondary particles, the aggregation could be suppressed by covering the particles with graphene. The composite exhibited a specific capacity of 230 mA h g-1, and could be cycled more than 100 times without any large capacity loss even at a moderate current density with the Mg(ClO4)2/CH3CN electrolyte.
- Kobayashi, Hiroaki,Yamaguchi, Kazuya,Honma, Itaru
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- Particle size control and self-assembly processes in novel colloids of nanocrystalline manganese oxide
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The synthesis of semiconducting nanocrystals of manganese oxide of controlled sizes and their manipulation to form ordered arrays is described. Nanocrystalline mixed-valent manganese oxides have been prepared as colloidal solutions via reduction of tetraalkylammonium (methyl, ethyl, propyl, and butyl) permanganate salts in aqueous solutions with 2-butanol and ethanol. Reduction with the poorly water miscible 2-butanol produces aqueous colloids for the methyl, ethyl, and propyl systems, whereas 2-butanol colloids are produced for the butyl system. The colloids are reddish-brown, have an average manganese oxidation state of 3.70-3.79, and have been prepared in manganese concentrations up to 0.57 M. The sols will gel upon aging, and the gel time depends on the cation, the amount of alcohol, the temperature, and the concentration of manganese. Small angle neutron scattering (SANS) data indicate that the particles are disklike in shape with radii in the range 20-80 A and are largely unassociated in solution. Thin films produced from evaporation of the colloid or spreading of the gel onto glass slides demonstrate long-range order, yielding an X-ray diffraction (XRD) pattern consistent with a structure of Cdl2-type layers of manganese oxide with tetraalkylammonium cations and water molecules interspersed between the layers. The SANS and XRD evidence are consistent with a mechanism of self-assembly of unassociated layers upon concentration and evaporation. Consistent with a mechanism of quantum confinement, UV/visible spectroscopy of the colloids reveals two absorbances, one near 220 nm and the other in the range 290-310 nm, blue-shifted from the maxima observed for bulk manganese oxide (400 nm). When the samples are aged, these bands shift to the red. The growth of particles in solution with aging, indicated by the shifts in absorbance, has been confirmed by SANS experiments.
- Brock, Stephanie L.,Sanabria, Maria,Suib, Steven L.,Urban, Volker,Thiyagarajan, Pappannan,Potter, Donald I.
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- Synthesis, structure and magnetic properties of oxo-centered trinuclear manganese complex [Mn3O(O2CC3H7)6(C 5H5N)3]·ClO4
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The reaction of N-n-Bu4MnO4 with Mn(OAc)2·4H2O, pyridine and butyric acid in absolute EtOH leads to the high-yield formation of the oxo-centered trinuclear Mn complex, [Mn3O(O2CC3H7)6(C 5H5N)3]·ClO4. The complex crystallizes in orthorhombic, space group Pna21 with a=19.588(7), b=20.194(6), c=12.491(5) A. Variable temperature solid state magnetic susceptibility study shows that the antiferromagnetic exchange interaction is weak, and the exchange integral J=-12.36 cm-1.
- Li, Jun,Yang, Shuming,Zhang, Fengxing,Tang, Zongxun,Ma, Shulin,Shi, Qizhen,Wu, Qiangjin,Huang, Zixiang
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- Cholic acid derivative and application thereof in lowering cholesterol
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The invention discloses a cholic acid derivative as shown in a formula (I) and a preparation method thereof, and the target product cholic acid derivative is prepared through reactions such as TBS protection, 4, 4-dimethylation, deprotection, oxidation, Witting reaction, reduction, hydrolysis, acylation and deprotection. The invention further provides an application of the cholic acid derivative in preparation of drugs for preventing and/or treating hypercholesteremia and hypertriglyceridemia, resisting atherosclerosis and resisting non-alcoholic steatohepatitis, the cholic acid derivative can effectively promote degradation of hydroxymethyl glutaryl-coenzyme A reductase (3-hydroxy-3-methyl-glutaryl-coenzyme A reductase, HMGCR), and reduce HMGCR protein increase caused by statins, so that the endogenous cholesterol level is reduced, a beneficial reference is provided for research and development of new cholesterol-reducing medicines, and the application prospect is good.
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Paragraph 0455-0456
(2021/10/30)
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- A synthetic model for the oxygen-evolving complex in Sr2+- containing photosystem II
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A novel heterometallic MnSr complex containing the Mn3SrO 4 cuboidal moiety and all types of μ-O2- moieties observed in the oxygen-evolving complex (OEC) in Sr2+-containing photosystem II (PSII) has been synthesized and characterized, which provides a new synthetic model of the OEC.
- Chen, Changhui,Zhang, Chunxi,Dong, Hongxing,Zhao, Jingquan
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supporting information
p. 9263 - 9265
(2014/08/05)
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- Manganese complexes of α-hydroxy acids
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Manganese complexes of α-hydroxy acids (H2L) have been implicated in the basidomycete oxidative degradation pathway of lignin. In this contribution, we evaluate the chemistry of manganese(III) and manganese(IV) α-hydroxy acid compounds using lactic acid (H2Lc), 2-hydroxy-2-ethylbutyric acid (H2HEB), and 2-hydroxyisobutyric acid (H2HIB). Both oxidative and reductive methodologies to give compounds of stoichiometry (Cat)3[(Cat)MnIV2L6], (Cat)3[MnIII2(L)4HL] and (Cat)2[MnIII(L)2HL] have been explored. The X-ray structure of 1, Na3[NaMnIV2(HIB)6]·4MeOH, which was prepared by the reaction of MnCl2, H2HIB, and NaOCH3 in methanol, reveals a mixed-metal trinuclear cluster composed of two Mn(IV) octahedra that are bridged by a sodium ion. The face-shared geometry leads to a very short Mn-Na distance (2.98 A?). 1 is a unique Mn(IV) complex with all oxygen ligation and containing redox-innocent ligands. The O(3)O(3′) coordination shell is trigonally compressed along the face containing the three alkoxide ligands. The X-band EPR spectrum of 1 at 100 K is consistent with an isolated S = 3/2 spin system. The Mn(III) dimer (TMA)3[MnIII2(Lc)4HLc]·H 2O (5) can be prepared by the reaction of tetramethylammonium permanganate ((TMA)MnO4), H2Lc, and (TMA)OH in methanol. An excess of ligand allows for the reduction of the Mn(VII) to Mn(III). The X-ray structure of 5 provides the first example of an Mn(III) dimer with axial compression. Two MnIIILc2 units, having a propeller configuration, are bridged by the carboxylate of an HLc-, having a protonated hydroxyl oxygen atom, and weak bridges from coordinated alkoxides of the adjacent MnIIILc2 unit. The Mn-Mn separation is 3.09 A?. A third compound of composition (Cat)2[MnIII(L)2HL] has also been prepared by both reductive and oxidative methodologies and is most likely an infinite chain structure that has a trans-MnIIIL2 plane that is linked by the anti-anti coordination of carboxylate oxygens of an HL-. The relevance of these manganese α-hydroxy acid complexes to structural proposals for the oxygen-evolving complex and diffusible intermediates of the manganese lignin peroxidase is discussed. X-ray parameters for Na3[NaMnIV2(HIB)6]·4MeOH (1) Na4Mn2C28H52O22: 942.6 g/mol, triclinic crystal system, P1, a = 9.549 (6) A?, b = 9.843 (4) A?, c = 13.966 (8) A?, α = 108.12 (4)°, β = 76.44 (5)°, γ = 119.61 (4)°, V = 1079 (1) A?3, Z = 1, 2845 data collected with 3° 3σ(I), R = 0.057, Rw = 0.058. X-ray parameters for (TMA)3[MnIII2(Lc)4HLc]·H 2O (5), Mn2C27H59N3O16: 791 g/mol, monoclinic crystal system, P21, a = 11.425 (6) A?, b = 15.214 (10) A?, c = 12.108 (4) A?, β = 106.45 (3)°, V = 2018 (2) A?3, Z = 2, 2767 data collected with 3° 3σ(I), R = 0.057, Rw = 0.058.
- Saadeh, Salman M.,Lah, Myoung Soo,Pecoraro, Vincent L.
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- Preparation and Physical Properties of Trinuclear Oxo-Centered Manganese Complexes of the General Formulation 0,+ (R=Me or Phe; L= a Neutral Donor Group) and the Crystal Structures of (pyr) and *0.5MeCN
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The reaction of N-n-Bu4MnO4 with appropriate reagents in nonaqueous solvents leads to the high-yield formation of trinuclear oxo-centered Mn complexes of general formulation z+ (1, R=Me, L=pyr, z=1; 2, R=Me, L=pyr, Z=0, monopyridine solvate; 3, R=Me, L=pyr, z=0, unsolvated; 4, R=Ph, L3=(pyr)2(H2O), z=0; 5, R=Me, L=HIm, z=1; pyr=pyridine, HIm=imidazole).The crystal structures of complexes 2 and 4 have been determined.Complex 2 crystallizes in rhombohedral space group R32 with (at -50 deg C) a=b=17.552(6) Angstroem, c=10.918(3) Angstroem, γ=120.00(1) deg, and Z=3.A total of 1546 unique data with F>3?(F) were refined to conventional values of R and Rw of 5.77 and 5.68percent respectively.Complex 4 crystallizes in monoclinic space group P21 with (at -156 deg C) a=15.048(10) Angstroem, b=23.600(17) Angstroem, c=14.959(10) Angstroem, β=91.01(3) deg, and Z=2.A total of 7174 unique data with F>3?(F) were refined to values of R and Rw of 8.64 and 8.43percent, respectively.Both 2 and 4 possesses an oxo-centered Mn3O unit characteristic of "basic carboxylates" with peripheral ligation provided by bridging carboxylate and terminal pyr (or H2O) groups.Each Mn is distorted octahedral, and consideration of overall charge of the trinuclear units necessitates a mixed-valence MnIIMn2III description.In 2, the presence of a C3 axis through the central O and perpendicular to the Mn3O unit necessitates the Mn centers to be crystallographically equivalent, suggesting rapid intramolecular electron transfer or electronic delocalization.In contrast, 4 possesses no imposed symmetry elements and is in a trapped-valence situation in accord with its mixed-ligand nature, since two Mn centers have a terminal pyr group while the third Mn has a terminal H2O molecule.The latter metal center is assigned as the MnII ion based on its longer metal-ligand distances.Variable temperature solid state magnetic susceptibility studies have been performed on 1-4 in the temperature range of ca. 6 to ca. 340 K.Satisfactory fits to the observed susceptibility data have been obtained by assuming isotropic magnetic exchange interactions and employing the appropriate spin Hamiltonians and derived susceptibility equations.All Mn centers are shown to be in high-spin electronic configurations and to be antiferromagnetically coupled.The derived exchange parameters are all relatively small in magnitude, (J)-1.In addition, it is found that the antiferromagnetic exchange interactions are smaller for the Mn3O units than those for isostructural Fe3O systems, and a rationalization is proposed.Since phase transitions had previously been characterized by heat capacity measurements on (pyr), isostructural complex 2 was investigated by differential scanning calorimetry (DSC) in the temperature range 153-303 K.An exothermic thermal effect is clearly evident with a peak at 184.7 K in the cooling curve (the other mixed-valence Mn3O systems showed no thermal effects in their DSC thermograms).The origin of this thermal effect and comparisons..
- Vincent, John B.,Chang, Hsiu-Rong,Folting, Kirsten,Huffman, John C.,Christou, George,Hendrickson, David N.
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p. 5703 - 5711
(2007/10/02)
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- Hydrates of Organic Compounds. VII. The Effect of Anions on the Formation of Clathrate Hydrates of Tetrabutylammonium Salts
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Phase diagrams of the binary mixtures of tetrabutylammonium salt nX (X = NO2, NO3, BrO3, ClO3, IO3, ClO4, MnO4, and NCS for n = 1; X = CO3, SO4, WO4, and CrO4 for n = 2; and X = PO4 for n = 3) with water were determined over the temperature range between -10 and +50 deg C.From these diagrams the following results were obtained: (1) the formation of a clathrate-like hydrate for salts having such anions as NO2-, NO3-, BrO3-, ClO3-, IO3-, SO42- and PO43- was newly confirmed; (2) the melting point of the clathrate hydrate of the salt with monovalent anion was appreciably influenced by the kind of anion; (3) in the hydrates of the salt having either di- or trivalent anions, the melting points were relatively high and were only slightly affected by the kind of anion; (4) the crystal structure of these hydrates was essentially the same as that of the tetrabutylammonium fluoride hydrate, judging from the hydration numbers; (5) the solubilities in water of both permanganate and perchlorate were markedly lower than that of the iodide; and (6) in the thiocyanate system a phase separation into two liquid phases was observed at temperatures higher than +3.5 deg C.The effect of a monovalent anion on the stability of the clathrate hydrate was discussed in connection with the conventional partial molal volume of the anion.
- Nakayama, Haruo
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p. 877 - 880
(2007/10/02)
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