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81.
82.
Al-Kadamany GA Hussain F Mal SS Dickman MH Leclerc-Laronze N Marrot J Cadot E Kortz U 《Inorganic chemistry》2008,47(19):8574-8576
We have synthesized the cyclic Ti 9 Keggin trimers [(alpha-Ti 3PW 9O 38) 3(PO 4)] (18-) ( 1) and [(alpha-Ti 3SiW 9O 37OH) 3(TiO 3(OH 2) 3)] (17-) ( 2), which are both composed of three (Ti 3XW 9O 37) units (X = P or Si) linked via three Ti-O-Ti bridges and a capping group, which is either tetrahedral PO 4 ( 1) or octahedral TiO 6 ( 2). Polyanions 1 and 2 were fully characterized in the solid state (IR, X-ray diffraction, thermogravimetric and elemental analyses) and in solution ( (31)P or (183)W NMR). 相似文献
83.
Bassil BS Mal SS Dickman MH Kortz U Oelrich H Walder L 《Journal of the American Chemical Society》2008,130(21):6696-6697
We have synthesized and structurally characterized the unprecedented peroxo-zirconium(IV) containing [Zr6(O2)6(OH)6(gamma-SiW10O36)3]18- (1). Polyanion 1 comprises a cyclic 6-peroxo-6-zirconium core stabilized by three decatungstosilicate units. We have also prepared the isostructural hafnium(IV) analogue [Hf6(O2)6(OH)6(gamma-SiW10O36)3]18- (2). We investigated the acid/base and redox properties of 1 by UV-vis spectroscopy and electrochemistry studies. Polyanion 1 represents the first structurally characterized Zr-peroxo POM with side-on, bridging peroxo units. The simple, one-pot synthesis of 1 and 2 involving dropwise addition of aqueous hydrogen peroxide could represent a general procedure for incorporating peroxo groups into a large variety of transition metal and lanthanide containing POMs. 相似文献
84.
Mal SS Dickman MH Kortz U Todea AM Merca A Bögge H Glaser T Müller A Nellutla S Kaur N van Tol J Dalal NS Keita B Nadjo L 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(4):1186-1195
The 16-Fe(III)-containing 48-tungsto-8-phosphate [P(8)W(48)O(184)Fe(16)(OH)(28)(H(2)O)(4)](20-) (1) has been synthesised and characterised by IR and ESR spectroscopy, TGA, elemental analyses, electrochemistry and susceptibility measurements. Single-crystal X-ray analyses were carried out on Li(4)K(16)[P(8)W(48)O(184)Fe(16)(OH)(28)(H(2)O)(4)]66 H(2)O2 KCl (LiK-1, orthorhombic space group Pnnm, a=36.3777(9) A, b=13.9708(3) A, c=26.9140(7) A, and Z=2) and on the corresponding mixed sodium-potassium salt Na(9)K(11)[P(8)W(48)O(184)Fe(16)(OH)(28)(H(2)O)(4)].100 H(2)O (NaK-1, monoclinic space group C2/c, a=46.552(4) A, b=20.8239(18) A, c=27.826(2) A, beta=97.141(2) degrees and Z=4). Polyanion 1 contains--in the form of a cyclic arrangement--the unprecedented {Fe(16)(OH)(28)(H(2)O)(4)}(20+) nanocluster, with 16 edge- and corner-sharing FeO(6) octahedra, grafted on the inner surface of the crown-shaped [H(7)P(8)W(48)O(184)](33-) (P(8)W(48)) precursor. The synthesis of 1 was accomplished by reaction of different iron species containing Fe(II) (in presence of O(2)) or Fe(III) ions with the P(8)W(48) anion in aqueous, acidic medium (pH approximately 4), which can be regarded as an assembly process under confined geometries. One fascinating aspect is the possibility to model the uptake and release of iron in ferritin. The electrochemical study of 1, which is stable from pH 1 through 7, offers an interesting example of a highly iron-rich cluster. The reduction wave associated with the Fe(III) centres could not be split in distinct steps independent of the potential scan rate from 2 to 1000 mV s(-1); this is in full agreement with the structure showing that all 16 iron centres are equivalent. Polyanion 1 proved to be efficient for the electrocatalytic reduction of NO(x), including nitrate. Magnetic and variable frequency EPR measurements on 1 suggest that the Fe(III) ions are strongly antiferromagnetically coupled and that the ground state is tentatively spin S=2. 相似文献
85.
86.
Addition of 1,2‐phenylenediamine to solutions ofbis(1,1,1,5,5,5‐hexafluoropentane‐2,4‐dionato‐O,O′)cobalt(II),‐iron(II) and ‐nickel(II) resulted in crystals containing centrosymmetric octahedral complexes with two amines per metal atom. In all three isostructural complexes, i.e. [M(C5HF6O2)2(C6H8N2)2] where M = Fe, Cu and Ni, the two C—N bonds differ significantly in length by an average of 0.031 (3) Å. The phenyl C—C bonds display a pattern of small differences, the C—C bond between the amines being longer than the shortest phenyl C—C bonds by an average of 0.022 (4) Å. 相似文献
87.
Nikolay N. Sveshnikov Michael H. Dickman Michael T. Pope 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(10):1193-1195
The title structure, [Rh2(C7H5O3)4(C2H6OS)2]·[Rh2(C4H7O2)4(C2H6OS)2]·2C2H6O, contains two discrete neutral Rh–Rh dimers cocrystallized as the ethanol disolvate. Each dimer is situated on an inversion center. The butyrate chain displays disorder in one C‐atom position. In each dimer, the dimethyl sulfoxide ligand (dmso) is bound via S, as expected. The ethanol is a hydrogen‐bond acceptor for one p‐hydroxybenzoate hydroxyl group and acts as a hydrogen‐bond donor to the dmso O atom of a neighboring p‐hydroxybenzoate dirhodium complex. A third hydrogen bond is formed from the other p‐hydroxybenzoate hydroxyl group to the dmso O atom of a butyrate–dirhodium complex. 相似文献
88.
Ambrosius P. L. Snijders Ming-Lung Hung Stuart A. Wilson Mark J. Dickman 《Journal of the American Society for Mass Spectrometry》2010,21(1):88-96
Arginine and lysine methylation are widespread protein post-translational modifications. Peptides containing these modifications
are difficult to retain using traditional reversed-phase liquid chromatography because they are intrinsically basic/hydrophilic
and often fragment poorly during collision induced fragmentation (CID). Therefore, they are difficult to analyze using standard
proteomic workflows. To overcome these caveats, we performed peptide separations at neutral pH, resulting in increased retention
of the hydrophilic/basic methylated peptides before identification using MS/MS. Alternatively trifluoroacetic acid (TFA) was
used for increased trapping of methylated peptides. Electron-transfer dissociation (ETD) mass spectrometry was then used to
identify and characterize methylated residues. In contrast to previous reports utilizing ETD for arginine methylation, we
observed significant amount of side-chain fragmentation. Using heavy methyl stable isotope labeling with amino acids in cell
culture it was shown that, similar to CID, a loss of monomethylamine or dimethylamine from the arginine methylated side-chain
during ETD can be used as a diagnostic to determine the type of arginine methylation. CID of lysine methylated peptides does
not lead to significant neutral losses, but ETD is still beneficial because of the high charge states of such peptides. The
developed LC MS/MS methods were successfully applied to tryptic digests of a number of methylated proteins, including splicing
factor proline-glutamine-rich protein (SFPQ), RNA and export factor-binding protein 2 (REF2-I) and Sul7D, demonstrating significant
advantages over traditional LC MS/MS approaches. 相似文献
89.
The skew angle causes a discrepancy in determining the reader-to-writer offset (RWO) when using different periodical patterns in track profile tests. It also separates the peak overwrite (OW) from the peak high frequency amplitude HFA, (1 T periodical pattern) on corresponding track profiles. Furthermore, higher track density and larger skew angle exacerbate the skew effect and induce more RWO error, thus impacting the parametric performance optimization. Simulation studies are used to interpret the skew effect on the RWO determination and OW cross-track characteristics. Based on experimental investigations and simulation analyses, using the HFA, track profile for deriving the optimal RWO is proposed for spin-stand tests. Actual parametric characterization has proven that the optimal RWO minimized the skew effect and the RWO error, thus improving the parametric performance and reducing the test variation. The method is beneficial and necessary for the high track density characterization. 相似文献
90.
Monte Carlo optimization 总被引:2,自引:0,他引:2
Monte Carlo optimization techniques for solving mathematical programming problems have been the focus of some debate. This note reviews the debate and puts these stochastic methods in their proper perspective. 相似文献