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41.
Taylor SM McIntosh RD Beavers CM Teat SJ Piligkos S Dalgarno SJ Brechin EK 《Chemical communications (Cambridge, England)》2011,47(5):1440-1442
Phosphinate ligands allow for the transformation of a calix[4]arene supported [Mn(III)(2)Mn(II)(2)] tetramer cluster motif into an unusual [Mn(III)Mn(II)](2) dimer of dimers; the clusters self-assemble in the crystal to form bi-layer arrays reminiscent of the typical packing of calixarene solvates. 相似文献
42.
Yang H Jin H Zhen H Wang Z Liu Z Beavers CM Mercado BQ Olmstead MM Balch AL 《Journal of the American Chemical Society》2011,133(16):6299-6306
Four isomers with the composition SmC(90) were obtained from carbon soot produced by electric arc vaporization of carbon rods doped with Sm(2)O(3). These were labeled Sm@C(90)(I), Sm@C(90)(II), Sm@C(90)(III), and Sm@C(90)(IV) in order of their elution times during chromatography on a Buckyprep column with toluene as the eluent. Analysis of the structures by single-crystal X-ray diffraction on cocrystals formed with Ni(octaethylporphyrin) reveals the identities of the individual isomers as follows: I, Sm@C(2)(40)-C(90); II, Sm@C(2)(42)-C(90); III, Sm@C(2v)(46)-C(90) and IV, Sm@C(2)(45)-C(90). This is the most extensive series of isomers of any endohedral fullerene to have their individual structures determined by single-crystal X-ray diffraction. The cage structures of these four isomers can be related pairwise to one another in a formal sense through sequential Stone-Wales transformations. 相似文献
43.
Haddadin MJ El-Khatib M Shoker TA Beavers CM Olmstead MM Fettinger JC Farber KM Kurth MJ 《The Journal of organic chemistry》2011,76(20):8421-8427
We report the alkoxylation of methyl-substituted quinoxalino[2,3-c]cinnolines to give acetals and orthoesters in high yields. Routes to the precursors of this alkoxylation reaction as well as other quinoxalino[2,3-c]cinnoline and their 5-oxide derivatives are reported. Most of these quinoxalino[2,3-c]cinnolines were prepared by cyclization of the corresponding 2-amino-3-(2-nitrophenyl)quinoxaline, which, in turn, result from an unusual Beirut reaction from benzofurazan oxides plus 2-nitrobenzylcyanides. Mechanistic explanations for these intriguing reactions are presented. 相似文献
44.
This paper describes a new computational procedure for calculating eigenvalues and eigenvectors of a square matrix. The method is based on a matrix function, the sign of a matrix. Eigenvalues and eigenvectors of matrices with distinct eigenvalues and nondefective matrices with repeated roots can be determined in a straightforward manner. Defective matrices require additional calculations. 相似文献
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47.
AM Cardoso SM Alexandre CM Barros AJ Correia NM Nibbering 《Rapid communications in mass spectrometry : RCM》1999,13(19):1885-1888
The collision-induced dissociation (CID) of deprotonated arylalkylamines of general formula R(1)C(6)H(4)CHR(2)CH(2)NR(3)(2) (where R(1) = H, OH, F or NO(2); R(2) = H or OH; R(3) = H or CH(3)) generated by negative chemical ionization with H(2)O and D(2)O as ionizing reagents, is discussed. The negative chemical ionization mass spectra show that, in the absence of a hydroxy group in the aromatic ring, deprotonation takes place at the benzylic position whereas the proton is lost from the OH group when present. The nitro compound forms only M(-.) ions. The CID spectra of the deprotonated molecules show that fragmentations are strongly dependent on the structural features of the molecules, namely the presence or absence of substituents in the aromatic ring or aliphatic chain. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
48.
AM Johnston CM Scrimgeour MO Henry LL Handley 《Rapid communications in mass spectrometry : RCM》1999,13(14):1531-1534
The conversion of nitrate (NO(3)(-)) to 1-phenylazo-2-naphthol (Sudan-1) has been examined as a method for natural abundance measurement of delta(15)N of NO(3)(-). The reaction results in dilution of NO(3)(-)-N with only one reagent-derived N and the product is readily concentrated from dilute samples by reverse phase chromatography. There is systematic isotopic fractionation during the reaction, but this can be allowed for by analysing known NO(3)(-) standards along with each sample set. Sudan-1 prepared from surface water samples containing approximately 50 &mgr;g NO(3)(-)-N can be analysed by automated continuous flow isotope ratio mass spectrometry with a precision of 0.2 per thousand (one standard deviation) and the accuracy is not affected by interference from other nitrogenous species in the sample or reagents. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
49.
McIntosh RD Taylor SM Sanz S Beavers CM Teat SJ Brechin EK Dalgarno SJ 《Dalton transactions (Cambridge, England : 2003)》2011,40(45):12265-12270
A series of new sodium and mixed sodium/manganese clusters have been formed using p-tert-butylcalix[8]arene as a support. In all cases the calixarene adopts the pleated-loop conformation, and the resulting complexes show interesting self-assembly properties depending on the ligated solvent molecules around individual cluster cores. 相似文献
50.
The present paper studies the infiltration of an incompressible liquid in an initially dry (or partially dry), deformable sponge-like material made of an incompressible constituent in the slug-flow approximation having in mind the application to some industrial processes involving flow through sponge-like materials and, in particular, some composite materials manufacturing processes. The resulting initial-boundary value problem is of Stefan type, with suitable interface conditions and evolution equations describing the position of the interfaces delimiting the saturated region within the porous material. Different models are then suggested in the saturated region, depending on the importance of the inertial terms and on the constitutive equation for the stress. Comparison of the simulation with known experimental results is satisfactory. 相似文献