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191.
Gina M. Chiarella Doris Y. Melgarejo John P. Fackler Jr. 《Journal of Cluster Science》2012,23(3):823-838
The reaction of copper(I) tetra-acetonitrile hexaflourophosphate with LiTEhpp (the lithium salt of 3,3,7,7-tetraethyl-1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-??)pyrimidine) at low temperature (?80?°C) in THF under Schlenk conditions, produces a cluster salt tetrakis(3,3,9,9-tetraethyl-1,5,7-triazabicyclo[4.4.0]dec-4ene)bis(hexafluorophosphate)-hexa-copper(I), [Cu6(TEhpp)4)](PF6)2(1). The cation is composed of an octahedral core of six copper(I) with four TEhpp ligands, each in a tri-coordinating fashion through two N atoms. This compound shows strong luminescent properties at liquid nitrogen temperature and is soluble in non-polar solvents such as toluene and hexane. The synthesis, spectroscopic properties and crystal structure are presented and discussed. The use of CuCl for the reaction with LiTEhpp yields a solution from which, in the presence of water, two mononuclear copper structures are produced in low yield, [Cu(II){(??-O-(HTEhpp)2}2Cl][Cu(I)Cl2], 2, and Cu (TEhpp)2Cl, 3. 相似文献
192.
Three compounds are described from reactions of divalent nickel species and bicyclic guanidinate ligands. These compounds encompass a variety of nuclearities with one being triangular and having an hour-glass shape and the formula Ni3(tbn)6·2LiCl, 1, where tbn is a bicyclic guanidinate anion with fused 5/6 membered rings. A dinuclear compound [(??2-Imeth)Ni(??-tbo)]2Cl2, 2, contains two fused 5/5 membered rings (tbo) that bridge two divalent nickel atoms and also contains a chelating unit in each metal center. The neutral Imeth (1-(2,3,5,6-tetrahydro-1H-imidazo[1,2-a]imidazol-1-yl)ethanimine) is an imino-containing ligand produced by the Ni(II) catalyzed reaction of tbo with acetonitrile. A mononuclear species, [(??2-hpp)Ni(hpp)(Hhpp)]Cl, 3, is obtained from reaction of NiCl2 with the bicyclic guanidinate ligand with two fused six-member rings in contact with moisture. In all compounds each of the Ni atoms has a local square-planar arrangement common in d8 species. 相似文献
193.
Despite the importance of stating the measurement uncertainty in chemical analysis, concepts are still not widely applied
by the broader scientific community. The Guide to the expression of uncertainty in measurement approves the use of both the partial derivative approach and the Monte Carlo approach. There are two limitations to the partial
derivative approach. Firstly, it involves the computation of first-order derivatives of each component of the output quantity.
This requires some mathematical skills and can be tedious if the mathematical model is complex. Secondly, it is not able to
predict the probability distribution of the output quantity accurately if the input quantities are not normally distributed.
Knowledge of the probability distribution is essential to determine the coverage interval. The Monte Carlo approach performs
random sampling from probability distributions of the input quantities; hence, there is no need to compute first-order derivatives.
In addition, it gives the probability density function of the output quantity as the end result, from which the coverage interval
can be determined. Here we demonstrate how the Monte Carlo approach can be easily implemented to estimate measurement uncertainty
using a standard spreadsheet software program such as Microsoft Excel. It is our aim to provide the analytical community with
a tool to estimate measurement uncertainty using software that is already widely available and that is so simple to apply
that it can even be used by students with basic computer skills and minimal mathematical knowledge. 相似文献
194.
GM Friederichs I Schellenberg R Pöttgen V Duppel L Kienle JS Auf der Günne D Johrendt 《Inorganic chemistry》2012,51(15):8161-8167
The topochemical deintercalation of Na(+) ions from solid NaFeAs at room temperature in THF with iodine yields the superconducting phase Na(1-y)Fe(2-x)As(2) (T(c) ≈ 11 K). This metastable iron arsenide decomposes at 120 °C and is not accessible by high-temperature solid-state synthesis. X-ray powder diffraction confirms the ThCr(2)Si(2)-type structure, but reveals very small coherently scattering domains with a mean composition Na(0.9(2))Fe(1.7(1))As(2). HRTEM investigations show crystalline as well as strongly distorted areas with planar defects. The latter are probably due to sodium loss and disorder which is also detected by (23)Na solid state NMR. The (57)Fe-M?ssbauer spectrum of Na(1-y)Fe(2-x)As(2) shows one type of iron atoms in tetrahedral coordination. All results point to one crystallographic phase with very small domains due to fluctuations of the chemical composition. From electronic reasons we suggest the superconducting phase is presumably NaFe(2)As(2) in the ordered fractions of the sample. 相似文献
195.
Simonis AE Baumann-Pickering S Oleson E Melcón ML Gassmann M Wiggins SM Hildebrand JA 《The Journal of the Acoustical Society of America》2012,131(4):EL295-EL301
Killer whales in the North Pacific, similar to Atlantic populations, produce high-frequency modulated signals, based on acoustic recordings from ship-based hydrophone arrays and autonomous recorders at multiple locations. The median peak frequency of these signals ranged from 19.6-36.1 kHz and median duration ranged from 50-163 ms. Source levels were 185-193 dB peak-to-peak re: 1 μPa at 1 m. These uniform, repetitive, down-swept signals are similar to bat echolocation signals and possibly could have echolocation functionality. A large geographic range of occurrence suggests that different killer whale ecotypes may utilize these signals. 相似文献
196.
Lijuan J. Wang Margaret L. Grapperhaus Barnett S. Pitzele Timothy J. Hagen Kam F. Fok Jeffrey A. Scholten Dale P. Spangler Mihaly V. Toth Gina M. Jerome William M. Moore Pamela T. Manning James A. Sikorski 《Heteroatom Chemistry》2002,13(1):77-83
The efficient syntheses of two new types of conformationally constrained S‐[2‐[(1‐iminoethyl)amino]ethyl]homocysteine derivatives, 1‐amino‐3‐[2[(1‐iminoethyl)amino]ethylthio]cyclobutane carboxylic Acid ( 5 ) and (4S)‐4‐[[2‐[(1‐Iminoethyl)amino]ethyl]thio]‐L‐proline ( 6 ), are reported. These molecules represent the first attempts to probe conformational constraint near the α‐amino acid moiety of known homocysteine‐based inhibitors of nitric oxide synthase. Targets 5 and 6 were evaluated as potential inhibitors of the three human isoforms of nitric oxide synthase. © 2002 John Wiley & Sons, Inc. Heteroatom Chem 13:77–83, 2002; DOI 10.1002/hc.1109 相似文献