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101.
102.
H Yang H Jin X Wang Z Liu M Yu F Zhao BQ Mercado MM Olmstead AL Balch 《Journal of the American Chemical Society》2012,134(34):14127-14136
Three isomers of Sm@C(82) that are soluble in organic solvents were obtained from the carbon soot produced by vaporization of hollow carbon rods doped with Sm(2)O(3)/graphite powder in an electric arc. These isomers were numbered as Sm@C(82)(I), Sm@C(82)(II), and Sm@C(82)(III) in order of their elution times from HPLC chromatography on a Buckyprep column with toluene as the eluent. The identities of isomers, Sm@C(82)(I) as Sm@C(s)(6)-C(82), Sm@C(82)(II) as Sm@C(3v)(7)-C(82), and Sm@C(82)(III) as Sm@C(2)(5)-C(82), were determined by single-crystal X-ray diffraction on cocrystals formed with Ni(octaethylporphyrin). For endohedral fullerenes like La@C(82), which have three electrons transferred to the cage to produce the M(3+)@(C(82))(3-) electronic distribution, generally only two soluble isomers (e.g., La@C(2v)(9)-C(82) (major) and La@C(s)(6)-C(82) (minor)) are observed. In contrast, with samarium, which generates the M(2+)@(C(82))(2-) electronic distribution, five soluble isomers of Sm@C(82) have been detected, three in this study, the other two in two related prior studies. The structures of the four Sm@C(82) isomers that are currently established are Sm@C(2)(5)-C(82), Sm@C(s)(6)-C(82), Sm@C(3v)(7)-C(82), and Sm@C(2v)(9)-C(82). All of these isomers obey the isolated pentagon rule (IPR) and are sequentially interconvertable through Stone-Wales transformations. 相似文献
103.
Solutions containing the components Au(+), dpae (dpae is 1,2 bis-(diphenylarsino)ethane), and X(-) (X is Cl, Br, or I) can produce two different types of crystals with the composition Au(2)(μ-dpae)X(2): colorless blocks and colorless needles. Crystallographic studies of these crystals show that they are polymorphs with different structural motifs. In the α-polymorphs, which are isostructural, individual molecules of Au(2)(μ-dpae)X(2) form discrete dimers through two identical Au···Au contacts. In the β-polymorphs, which each have unique crystallographic parameters, the Au(2)(μ-dpae)X(2) molecules assemble into polymeric chains through aurophilic interactions. The Au···Au contacts in the α-polymorph (3.1163(2), 3.1064(3), and 3.0842(2) ? for Cl, Br, I, respectively) are somewhat shorter than those in the β-polymorph (3.1668(3), 3.1042(8), and 3.1046(2) for Cl, Br, I respectively). The systematic study we now report shows an increase in the strength of this aurophilic interaction for the α-form in the series X = Cl < Br < I, which is in good agreement with theoretical studies by Pyykk? and his co-workers. 相似文献
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Imran Ali Zeid A. AL‐Othman Norikaju Nagae Vinay D. Gaitonde Kamlesh K. Dutta 《Journal of separation science》2012,35(23):3235-3249
New generation columns, i.e. packed with superficially porous silica particles are available as trade names with following manufacturers: Halo, Ascentis Express, Proshell 120, Kinetex, Accucore, Sunshell, and Nucleoshell. These provide ultra‐fast HPLC separations for a variety of compounds with moderate sample loading capacity and low back pressure. Chemistries of these columns are C8, C18, RP‐Amide, hydrophilic interaction liquid chromatography, penta fluorophenyl (PFP), F5, and RP‐aqua. Normally, the silica gel particles are of 2.7 and 1.7 μm as total and inner solid core diameters, respectively, with 0.5‐μm‐thick of outer porous layer having 90 Å pore sizes and 150 m2/g surface area. This article describes these new generation columns with special emphasis on their textures and chemistries, separations, optimization, and comparison (inter and intra stationary phases). Besides, future perspectives have also been discussed. 相似文献
106.
Ateyyah M. AL‐Baradi Matthew Mears Richard A. L. Jones Mark Geoghegan 《Journal of Polymer Science.Polymer Physics》2012,50(18):1286-1292
We describe an investigation of fluorescence correlation spectroscopy into the diffusion of fluorescein‐tagged dextran (FDEX) in a poly(methacrylic acid) (PMAA) hydrogel. The temperature dependence of FDEX diffusion is shown to follow Zimm behavior in pure water, and the decrease in the diffusion coefficient when in the PMAA hydrogel has been modeled. The addition of acid and alkali (HCl and NaOH, respectively) not only control the swelling and collapse of the hydrogel but also reveal a strong pH dependence of the dextran diffusion coefficient, which shows a (nonmonatonic) increase with pH. The addition of NaCl and CaCl2 salts similarly showed evidence of network swelling, most notably at low salt concentration, but also that the diffusion coefficient within the gel at these low concentrations is larger than that in the equivalent solution without the hydrogel, indicating that the combination of hydrogel and salt works to increase the diffusion coefficient above that in pure water. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012 相似文献
107.
Daniel T. Walters Dr. Xian B. Powers Prof. Marilyn M. Olmstead Prof. Alan L. Balch 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(15):3849-3857
Two new molecular boxes, the mono-bromo box [Au6(Triphos)4Br](SbF6)5⋅6(CH2Cl2), 4 mB , and the dibromo box, [Au6(Triphos)4Br2⋅H2O](SbF6)4⋅4(CH2Cl2), 5 dB , have been prepared in crystalline form. Although constructed from non-luminescent components, both are strongly luminescent. Like its chloro counterpart, the mono-bromo box [Au6(Triphos)4Br](SbF6)5⋅6(CH2Cl2), 4 mB , is mechanochromic. Under grinding, it loses its luminescence. The bromo-bridged helicate, [(μ-Br){Au3(Triphos)2}2](CF3SO3)5⋅2(CH2Cl2), 3μ-H , with a cation that is isomeric with the box [Au6(Triphos)4Br]5+, has also been prepared and crystallographically characterized. Unlike its chloro analogue, [(μ-Br){Au3(Triphos)2}2](CF3SO3)5⋅2(CH2Cl2) is not luminescent. Thus, the cation produced upon grinding may be the cation present in the bromo-bridged helicate, [(μ-Br){Au3(Triphos)2}2](CF3SO3)5⋅2(CH2Cl2), 3μ-H . The dibromo box, [Au6(Triphos)4Br2⋅H2O](SbF6)4⋅4(CH2Cl2), 5 dB , is not significantly mechanochromic. 相似文献
108.
Beavers CM Jin H Yang H Wang Z Wang X Ge H Liu Z Mercado BQ Olmstead MM Balch AL 《Journal of the American Chemical Society》2011,133(39):15338-15341
An extensive series of soluble dilanthanum endohedral fullerenes that extends from La(2)C(90) to La(2)C(138) has been discovered. The most abundant of these, the nanotubular La(2)@D(5)(450)-C(100), has been isolated in pure form and characterized by single-crystal X-ray diffraction. 相似文献
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