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81.
Maheswaran Hariharasarma Charles H. Lake Charles L. Watkins Gary M. Gray 《Journal of organometallic chemistry》1999,580(2):1541
Chlorodiphenylphosphine and 2,2′-biphenylylenephosphorochloridite react with 2-hydroxy-2′-(1,4-bisoxo-6-hexanol)-1,1′-biphenyl to yield the new α,ω-bis(phosphorus-donor)-polyether ligands, 2-Ph2PO(CH2CH2O)2–C12H8-2′-OPPh2 (1) and 2-(2,2′-O2C12H8)P(CH2CH2O)2–C12H8-2′-P(2,2′-O2C12H8) (2). These ligands react with Mo(CO)4(nbd) to form the monomeric metallacrown ethers, cis-Mo(CO)4{2-Ph2PO(CH2CH2O)2–C12H8-2′-OPPh2} (cis-3) and cis-Mo(CO)4{2-(2,2′-O2C12H8)P(CH2CH2O)2–C12H8-2′-P(2,2′-O2C12H8)} (cis-4), in good yields. The X-ray crystal structures of cis-3 and cis-4 are significantly different, especially in the conformation of the metal center and the adjacent ethylene group. The very different 13C-NMR coordination chemical shifts of this ethylene group in cis-3 and cis-4 suggest that the solution conformations of these metallacrown ethers are also quite different. Both metallacrown ethers undergo cis–trans isomerization in the presence of HgCl2. Although the cis–trans equilibrium constants for the isomerization reactions are nearly identical, the isomerization of cis-3 is more rapid. Phenyl lithium reacts with cis-3 to form the corresponding benzoyl complexes but does not react with either trans-3 or cis-4. Both the slower rate of cis–trans isomerization of cis-4 and its lack of reaction with PhLi are consistent with weaker interactions between the hard metal cations and the carbonyl oxygens in both trans-3 and cis-4. 相似文献
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Cigdem O. Metin Larry W. Lake Caetano R. Miranda Quoc P. Nguyen 《Journal of nanoparticle research》2011,13(2):839-850
In this study, we present quantification methods for nanoparticle stability analysis using non-intrusive analytical techniques:
attenuated total reflectance, Fourier transform infrared (ATR-FTIR) spectroscopy, ultraviolet–visible (UV–vis) spectrophotometer,
zeta potential analyses, and dynamic light scattering (DLS). We use these techniques to study the stability of silica nanoparticle
dispersions and the effects of pH, temperature, and electrolytes that would be encountered in oil field brines in a reservoir.
Spectral analysis of the Si–O bond at wavenumber of 1110 cm−1 with the ATR-FTIR indicates a structural change on the surface of silica particles as the dispersion pH changes, which agrees
with zeta potential measurements. We define a critical salt concentration (CSC) for different salts, NaCl, CaCl2, BaCl2, and MgCl2, above which the silica dispersion becomes unstable. Three distinct stages of aggregation occur in the presence of salt:
clear dispersed, turbid, and separated phases. Divalent cations Mg2+, Ca2+, and Ba2+ are more effective in destabilizing silica nanoparticle dispersion than the monovalent cation Na+. The CSC for Na+ is about 100 times more than for Ca2+, Ba2+, and Mg2+. Among the divalent cations studied, Mg2+ is the most effective in destabilizing the silica particles. The CSC is independent of silica concentration, and lowers at
high temperature. 相似文献
84.
W. J. Oldham Jr. B. S. Matteson J. L. Miller C. T. Lake M. Attrep Jr. 《Journal of Radioanalytical and Nuclear Chemistry》2013,296(2):889-892
Discarded rusty iron objects in the environment adsorb trace plutonium mobilized by oxygenated surface waters (e.g. rain, snow melt). Radiochemical and mass spectrometric analysis of the surface oxide coating of modest collections of rusty nails retrieved from remote locations provides a global fallout plutonium signal of up to 2 × 1010 atoms of 239Pu per sample. The median 239Pu measurement for 10 samples from five locations was 2.82 × 109 atoms. The average 240Pu/239Pu atom ratio was 0.176 ± 0.012, consistent with the value accepted for global fallout. 相似文献
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A detailed numerical integration of the Oppenheimer-Volkoff equations for isothermal partially degenerate neutral lepton configurations shows that the mass distribution of the dark halo around the giant elliptical galaxy M87, as revealed by X-ray observations, can be very naturally accounted for, in detail, by an atmosphere of (10–50 eV) neutrinos. 相似文献
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