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71.
William H. Watson Guanmin Wu Michael G. Richmond 《Journal of organometallic chemistry》2008,693(8-9):1439-1448
Me3NO activation of the tetrairidium cluster Ir4(CO)12 (1) in presence of the diphosphine ligand 4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione (bpcd) furnishes the bpcd-substituted clusters Ir4(CO)10(bpcd) (3) and Ir4(CO)8(bpcd)2 (4) as the minor and major products, respectively. Cluster 3 has been isolated as the sole observable product from the reaction of [Ir4(CO)11Br][Et4N] (2) with bpcd in presence of AgBF4 at room temperature. Both 3 and 4 have been isolated and fully characterized in solution by spectroscopic methods. The solid-state structure of 3 reveals that the ancillary bpcd ligand is bound to a single iridium center, with chelating and bridging bpcd ligands found in the X-ray structure of cluster 4. Cluster 4 is unstable at room temperature and slowly loses CO to afford the hydride-bridged cluster HIr4(CO)4(μ-CO)3(bpcd)[μ-PhP(C6H4)CC(PPh2)C(O)CH2C(O)] (5). Cluster 5 has been fully characterized in solution by IR and NMR spectroscopies, and the C–H bond activation attendant in the ortho metalation step is shown to occur regioselectively at one of the aryl groups associated with the bridging bpcd ligand. The redox properties of clusters 3–5 have been explored and the electrochemical behavior discussed with respect to extended Hückel MO calculations and related diphosphine-substituted cluster compounds prepared by our groups. 相似文献
72.
Nitric acid plays an important role in the heterogeneous chemistry of the atmosphere. Reactions involving HNO(3) at aqueous interfaces in the stratosphere and troposphere depend on the state of nitric acid at these surfaces. The vapor/liquid interface of HNO(3)-H2O binary solutions and HNO(3)-H(2)SO(4)-H2O ternary solutions are examined here using vibrational sum frequency spectroscopy (VSFS). Spectra of the NO2 group at different HNO(3) mole fractions and under different polarization combinations are used to develop a detailed picture of these atmospherically important systems. Consistent with surface tension and spectroscopic measurements from other laboratories, molecular nitric acid is identified at the surface of concentrated solutions. However, the data here reveal the adsorption of two different hydrogen-bonded species of undissociated HNO(3) in the interfacial region that differ in their degree of solvation of the nitro group. The adsorption of these undissociated nitric acid species is shown to be sensitive to the H2O:HNO(3) ratio as well as to the concentration of sulfuric acid. 相似文献
73.
The interaction of EDTA with barium sulfate 总被引:1,自引:0,他引:1
Jones F Jones P Ogden MI Richmond WR Rohl AL Saunders M 《Journal of colloid and interface science》2007,316(2):553-561
Ethylenediaminetetraacetic acid (EDTA) is a known complexing agent that interacts with a host of cations. In this paper, various techniques are used to elucidate the mechanism of interaction between EDTA and barium sulfate surfaces. It is shown that complexation with metal ions is not sufficient to explain the inhibition of barite crystallization but that other processes such as chemisorption must also occur. EDTA is shown to always adsorb as the mono-protonated species - suggesting that the molecule is able to lose a proton when it adsorbs at lower pH. Molecular modelling shows that the interaction of the surface barium ions with the carboxylate group is an important one. Finally, in situ turbidity measurements provide information about the mechanism of nucleation/growth modification. It is found that the EDTA molecule inhibits barium sulfate nucleation and that this could be its primary means of inhibiting precipitation of barium sulfate. 相似文献
74.
We used Monte Carlo method to generate the configurations of disassembly of hot nucleus Au* based on the Atomic Mass Table and the conservation of mass and charge number.The resulted charge distribution of fragments was then used to calculate the conditional moments.The logarithm correlation between second and third moments of experimental charge distribution is very well reproduced by theory.It seems that no connection to the critical phenomenon of concerned system exists. 相似文献
75.
In this paper a simplified method for the calculation of average Coulomb energy in statistical model of the disassembly processes of hot nuclei is proposed.The effect of freeze-out volume is studied based on the assumption of Gaussion-like distribution.It is indecated that the centre and dispersion of Gaussion-like distribution somewhat reflect the location and the renge of liquid-gas coexistence phase. 相似文献
76.
J. Gr?ter P.A. Amaudruz R. Bilger P. Camerini J. Clark H. Clement E. Friedman L. Felawka S.N. Filippov E. Friagiacomo Y.K. Gavrilov E. Gibson N. Grion G.J. Hofman B. Jamieson T.L. Karavicheva M. KermaniPresent address: Sonigistix Corporation Richmond B.C. Canada VA-E--> E.L. Mathie R. Meier G. Moloney D. Ottewell J. P?tzold O. Patarakin K. Raywood R. Rui M. Schepkin M.E. Sevior G.R. Smith H. Staudenmaier R. Tacik G. Tagliente G.J. Wagner M. Yeomans 《The European Physical Journal A - Hadrons and Nuclei》1999,4(1):5-7
A search for the production of a bound trineutron state has been performed using the reaction 3He(π−,π+)nnn at incident pion energies of 65, 75, and 120 MeV. No evidence for the existence of the 3n was found, and an upper limit for the production cross section of approximately 30 nb/sr (2σ confidence level) was obtained.
Received: 22 October 1998 相似文献
77.
A. Kuhn I. J. Blewett D. P. Hand P. French M. Richmond J. D. C. Jones 《Optics and Lasers in Engineering》2000,34(4-6):273-288
This paper investigates the extension of optical fibre beam delivery to high-brightness applications, in particular laser percussion drilling, where both a good beam quality and high peak power are required. Beam quality preservation through a number of optical fibres is studied both experimentally and by using a ray propagation model. It is determined that in order to achieve the beam quality required for percussion drilling (M2<30) the largest fibre which can be used is 400 μm diameter. The laser-induced damage threshold is measured for a number of 400 μm fibres, and a CO2 laser-annealing technique is shown to increase the damage threshold by a factor of 10, allowing 28 J, 1 ms pulses to be transmitted. 相似文献
78.
79.
Shani Sperinck Thomas Becker Kate Wright William R. Richmond 《Journal of inclusion phenomena and macrocyclic chemistry》2009,65(1-2):89-95
A solvothermal method has been used to prepare hybrid inorganic–organic composites with a lamellar structure in which layers of wurtzite ZnS are separated by intercalated diamine molecules. A hybrid composite prepared with diethylenetriamine has been isolated and characterised and its structure and properties compared with those of the composite prepared using ethylenediamine. Comparative structural and morphological studies of the two lamellar hybrid composites are described on the basis of powder XRD, electron and scanning probe microscopies and thermal analysis of the materials. 相似文献
80.
The orientation and hydrogen bonding of water molecules in the vapor/water interfacial region in the presence of SO2 and CO2 gas are examined using vibrational sum-frequency spectroscopy (VSFS) to gain insight into the adsorption and reactions of these gases in atmospheric aerosols. The results show that an SO2 surface complex forms when the water surface is exposed to an atmosphere of SO2 gas. Reaction of SO2 with interfacial water leads to other spectral changes that are examined by studying the VSF spectra and surface tension isotherms of several salts added to the aqueous phase, specifically NaHSO3, NaHCO3, Na2SO3, Na2CO3, Na2SO4, and NaHSO4. The results are compared with similar studies of CO2 adsorption and reaction at the surface. A weakly bound surface complex is not observed with CO2. 相似文献