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71.
Kilgore UJ Stewart MP Helm ML Dougherty WG Kassel WS DuBois MR DuBois DL Bullock RM 《Inorganic chemistry》2011,50(21):10908-10918
A series of [Ni(P(R)(2)N(Ph)(2))(2)(CH(3)CN)](BF(4))(2) complexes containing the cyclic diphosphine ligands [P(R)(2)N(Ph)(2) = 1,5-diaza-3,7-diphosphacyclooctane; R = benzyl (Bn), n-butyl (n-Bu), 2-phenylethyl (PE), 2,4,4-trimethylpentyl (TP), and cyclohexyl (Cy)] have been synthesized and characterized. X-ray diffraction studies reveal that the cations of [Ni(P(Bn)(2)N(Ph)(2))(2)(CH(3)CN)](BF(4))(2) and [Ni(P(n-Bu)(2)N(Ph)(2))(2)(CH(3)CN)](BF(4))(2) have distorted trigonal bipyramidal geometries. The Ni(0) complex [Ni(P(Bn)(2)N(Ph)(2))(2)] was also synthesized and characterized by X-ray diffraction studies and shown to have a distorted tetrahedral structure. These complexes, with the exception of [Ni(P(Cy)(2)N(Ph)(2))(2)(CH(3)CN)](BF(4))(2), all exhibit reversible electron transfer processes for both the Ni(II/I) and Ni(I/0) couples and are electrocatalysts for the production of H(2) in acidic acetonitrile solutions. The heterolytic cleavage of H(2) by [Ni(P(R)(2)N(Ph)(2))(2)(CH(3)CN)](BF(4))(2) complexes in the presence of p-anisidine or p-bromoaniline was used to determine the hydride donor abilities of the corresponding [HNi(P(R)(2)N(Ph)(2))(2)](BF(4)) complexes. However, for the catalysts with the most bulky R groups, the turnover frequencies do not parallel the driving force for elimination of H(2), suggesting that steric interactions between the alkyl substituents on phosphorus and the nitrogen atom of the pendant amines play an important role in determining the overall catalytic rate. 相似文献
72.
The Caco-2 cell monolayer model was used to classify 13 compounds as P-glycoprotein (Pgp) substrates or non-substrates. The apparent permeability coefficients (Papp) in the basal-to-apical direction (PappB-A) and in the apical-to-basal direction (PappA-B) were determined for each compound and a compound was designated as a Pgp substrate if PappB-A/PappA-B, the permeability ratio, exceeded 2.0. The same compounds were chromatographed on open tubular glass columns containing membranes from cell lines that either expressed Pgp (Pgp(+)-OT column) or did not express Pgp (Pgp(−)-OT column). The differential retentions in min, Δt values, of the compounds were determined using the following relationship Δt = t(Pgp(+)-OT) − t(Pgp(−)-OT). A statistically significant correlation was observed between the Δt values and the permeability ratios, r2 = 0.7749 (p = 0.0063), indicating that the differential chromatography approach could be used to quantitatively assess permeability ratios. The results also indicated that a Δt value ≥0.5 min was a reliable measure of a permeability ratios >2 and could be used as a rapid qualitative determination of whether a test compound was a Pgp substrate. The chromatographic study took 1 h to complete and a single pair of columns could be used to screen at least 150 compounds a week and 600 compounds during the 4-week lifetime of the columns. 相似文献
73.
74.
Weiss CJ Groves AN Mock MT Dougherty WG Kassel WS Helm ML DuBois DL Bullock RM 《Dalton transactions (Cambridge, England : 2003)》2012,41(15):4517-4529
Molybdenum and tungsten bis(dinitrogen) complexes of the formula M(N(2))(2)(PNP)(2) (M = Mo and W) and W(N(2))(2)(dppe)(PNP), supported by diphosphine ligands containing a pendant amine of the formula (CH(2)PR(2))(2)NR' = P(R)N(R')P(R) (R = Et, Ph; R' = Me, Bn), have been prepared by Mg reduction of metal halides under an N(2) atmosphere. The complexes have been characterized by NMR and IR spectroscopy, X-ray crystallography, and cyclic voltammetry. Reactivity of the target Mo and W bis(dinitrogen) compounds with CO results in the formation of dicarbonyl complexes. 相似文献
75.
76.
Z. Ding D. W. Bullock P. M. Thibado V. P. LaBella Kieran Mullen 《Surface science》2003,540(2-3):491-496
The GaAs(0 0 1) surface is observed to evolve from being perfectly flat to a surface half covered with one-monolayer high spontaneously formed GaAs islands. The dynamics of this process are monitored with atomic-scale resolution using scanning tunneling microscopy. Surprisingly, pit formation dominates the early stages of island formation. Insight into the nucleation process is reported. 相似文献
77.
R. E. Bullock 《辐射效应与固体损伤》2013,168(2):107-112
Two types of commercially available carbon fibers (high tensile strength, HTS, and high modulus, HMS) were irradiated in the Ground Test Reactor in environments of air and of liquid nitrogen (LN2). The tensile strength of HTS fibers irradiated in air increased sharply above a fast-neutron fluence of 6 × 1017 n/cm2 (E> 1 MeV) and was 17 per cent greater than the strength of unirradiated control fibers at a fluence of 8.5 × 1017 n/cm2, but then the strengrh began to decrease for additional neutron exposure in air and fell 25 per cent below the control strength at the highest fluence of 4.5 × 1018 n/cm2. However, when irradiated in LN2 where surface oxidation did not take place, the room-temperature strength of HTS fibers continued to increase beyond 8.5 × 1017 n/cm2 and became almost 30 per cent greater than the control strength for a fluence of 3 × 1018 n/cm2. The tensile strength of HMS fibers irradiated in air increased slowly but steadily with neutron exposure and was only 4 per cent greater than the control strength at the highest fluence of 4.5 × 1018 n/cm2; the room-temperature strength of the HMS fibers decreased by 13 per cent when irradiated to a fluence of 3 × 1018 n/cm2 in LN2. 相似文献
78.
Raman spectroscopy can detect conformational changes in collagen structures and these findings are reviewed in this article. More specifically, some progressive diseases are mainly caused by alterations of collagen molecules but what is occurring at the biochemical level of this complex molecule usually remains unclear. While it may be true that a number of analytical techniques can analyze collagen, most of them have a series of limitations that limit their applicability to a wide range of samples. To understand in more detail the progression of a disease due to changes in the collagen structure, a technique that can detect subtle alterations at the biochemical level is needed. Raman spectroscopy is a label-free and noninvasive technique that can easily pick up on any conformational changes reflected primarily at the lipids, amides and proline and hydroxyproline regions. This review is the first compilation of studies of conformational changes in collagen molecules, providing help to understand changes in collagen biochemistry that can be of relevance to the human wound healing, ageing and pathologies. 相似文献
79.
Friedel–Crafts cyclization products were obtained using 1.1 equivalents of environmentally benign trichloroacetic anhydride as sole reagent and solvent. The resulting ketones included benzothiepins, benzothiopyrans, benzoxepins, dibenzothiepins, dibenzoxepins, and tetralones. 相似文献
80.
D. Bullock 《Commentarii Mathematici Helvetici》1997,72(4):521-542
Let M be a compact orientable 3-manifold. The set of characters of SL
2()-representations of forms a closed affine algebraic set. We show that its coordinate ring is isomorphic to a specialization of the Kauffman bracket
skein module, modulo its nilradical. This is accomplished by realizing the module as a combinatorial analog of the ring in
which tools of skein theory are exploited to illuminate relations among characters. We conclude with an application, proving
that a small manifold's specialized module is necessarily finite dimensional.
Received: April 18, 1996 相似文献