共查询到5条相似文献,搜索用时 15 毫秒
1.
Dubois L Caspar R Jacquamet L Petit PE Charlot MF Baffert C Collomb MN Deronzier A Latour JM 《Inorganic chemistry》2003,42(16):4817-4827
The dimanganese(II,II) complexes 1a [Mn(2)(L)(OAc)(2)(CH(3)OH)](ClO(4)) and 1b [Mn(2)(L)(OBz)(2)(H(2)O)](ClO(4)), where HL is the unsymmetrical phenol ligand 2-(bis-(2-pyridylmethyl)aminomethyl)-6-((2-pyridylmethyl)(benzyl)aminomethyl)-4-methylphenol, react with hydrogen peroxide in acetonitrile solution. The disproportionation reaction was monitored by electrospray ionization mass spectrometry (ESI-MS) and EPR and UV-visible spectroscopies. Extensive EPR studies have shown that a species (2) exhibiting a 16-line spectrum at g approximately 2 persists during catalysis. ESI-MS experiments conducted similarly during catalysis associate 2a with a peak at 729 (791 for 2b) corresponding to the formula [Mn(III)Mn(IV)(L)(O)(2)(OAc)](+) ([Mn(III)Mn(IV)(L)(O)(2)(OBz)](+) for 2b). At the end of the reaction, it is partly replaced by a species (3) possessing a broad unfeatured signal at g approximately 2. ESI-MS associates 3a with a peak at 713 (775 for 3b) corresponding to the formula [Mn(II)Mn(III)(L)(O)(OAc)](+) ([Mn(II)Mn(III)(L)(O)(OBz)](+) for 3b). In the presence of H(2)(18)O, these two peaks move to 733 and to 715 indicating the presence of two and one oxo ligands, respectively. When H(2)(18)O(2) is used, 2a and 3a are labeled showing that the oxo ligands come from H(2)O(2). Interestingly, when an equimolar mixture of H(2)O(2) and H(2)(18)O(2) is used, only unlabeled and doubly labeled 2a/b are formed, showing that its two oxo ligands come from the same H(2)O(2) molecule. All these experiments lead to attribute the formula [Mn(III)Mn(IV)(L)(O)(2)(OAc)](+) to 2a and to 3a the formula [Mn(II)Mn(III)(L)(O)(OAc)](+). Freeze-quench/EPR experiments revealed that 2a appears at 500 ms and that another species with a 6-line spectrum is formed transiently at ca. 100 ms. 2a was prepared by reaction of 1a with tert-butyl hydroperoxide as shown by EPR and UV-visible spectroscopies and ESI-MS experiments. Its structure was studied by X-ray absorption experiments which revealed the presence of two or three O atoms at 1.87 A and three or two N/O atoms at 2.14 A. In addition one N atom was found at a longer distance (2.3 A) and one Mn at 2.63 A. 2a can be one-electron oxidized at E(1/2) = 0.91 V(NHE) (DeltaE(1/2) = 0.08 V) leading to its Mn(IV)Mn(IV) analogue. The formation of 2a from 1a was monitored by UV-visible and X-ray absorption spectroscopies. Both concur to show that an intermediate Mn(II)Mn(III) species, resembling 4a [Mn(2)(L)(OAc)(2)(H(2)O)](ClO(4))(2), the one-electron-oxidized form of 1a, is formed initially and transforms into 2a. The structures of the active intermediates 2 and 3 are discussed in light of their spectroscopic properties, and potential mechanisms are considered and discussed in the context of the biological reaction. 相似文献
2.
Sensing and catalytic decomposition of hydrogen peroxide by silicon carbide nanotubes: A DFT study
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Roghaye Nurazar Zahra Fallah Ebrahimi Mehdi D. Esrafili Esmail Vessally 《International journal of quantum chemistry》2015,115(8):471-476
In this study, by carrying out detailed density functional theory calculations, we investigate the adsorption and stepwise decomposition of hydrogen peroxide (H2O2) over (6,0) and (7,0) zigzag silicon carbide nanotubes (SiCNTs). The results indicate that the H2O2 can be adsorbed on the exterior surface of the SiCNTs with noticeable adsorption energies and charge transfers. To gain insight into the catalytic activity of the surface, the interaction between the H2O2 and SiCNT is analyzed by detailed electronic analysis such as adsorption energy, charge density difference and activation barrier. The decomposition of H2O2 into O2 and H2 species can be viewed as the kinetically preferred reaction pathway for dehydrogenation of hydrogen peroxide over SiCNTs. There is also a curvature effect on the dehydrogenation kinetics of hydrogen peroxide, that small diameter SiCNTs with large curvature would be beneficial for decomposition of H2O2. © 2015 Wiley Periodicals, Inc. 相似文献
3.
Blanchard S Blain G Rivière E Nierlich M Blondin G 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(17):4260-4268
A new dinuclear manganese(II) complex was synthesised with the biscompartimental ligand 2,6-bis[bis(2-pyridylmethyl)aminomethyl]-4-nitrophenol (NO(2)BpmpH) and characterised by X-ray crystallography. Magnetic susceptibility measurements revealed that the two high-spin Mn(II) ions are antiferromagnetically coupled with a singlet-to-triplet separation of 7.2 cm(-1). The powder EPR spectra were recorded for both X- and Q-bands between 1.8 K and 35 K. A detailed analysis of these spectra led to the determination of three out of five individual spin-state zero-field splitting parameters. From the proposed simulations, the exchange coupling constant J and the intermetallic distance have been computed. 相似文献
4.
A novel Prussian blue (PB)‐Fe3O4 composite has been prepared for the first time by self‐template method using PB as the precursor. According to this method, Fe3O4 nanoparticles distributed uniformly on the surface of PB cube. The feed ratio of sodium acetate to PB has been proved to be a key factor for magnetic properties and electro‐catalysis properties of the composite. Under the experimental conditions, the saturation magnetization value (Ms) of PB‐Fe3O4–2 composite was 22 emug?1, while the Ms value of other samples reduced. The composites also showed a good peroxidase‐like activity for the oxidation of substrate 3,3,5,5‐tetramethylbenzidine (TMB) in the presence of H2O2. The catalytic reduction of hydrogen peroxide capacity was PB‐Fe3O4–1> PB‐Fe3O4–2> PB‐Fe3O4–3> PB‐Fe3O4–0, which confirmed the Fe(II) centres in PB surface and Fe3O4 nanoparticles had synergistic effect on catalytic reduction of hydrogen peroxide. 相似文献
5.
A. O. Terent"ev A. V. Kutkin M. M. Platonov I. I. Vorontsov M. Yu. Antipin Yu. N. Ogibin G. I. Nikishin 《Russian Chemical Bulletin》2004,53(3):681-687
Aliphatic and alicyclic gem-bis-hydroperoxides and their derivatives, bis(1-hydroperoxycycloalkyl) and bis(1-hydroperoxyalkyl) peroxides, dispiro- and tetraalkyl-1,2,4,5-tetroxanes were synthesized by the reaction of aliphatic and alicyclic acetals and enol ethers with H2O2 in the presence of BF3 in anhydrous Et2O. 相似文献