ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option. 相似文献
Abstract The energy shift of the He 11S0?21P1 transition, ΔE(n), can be used to determine the density, n, of He in bubbles in metals. A self-consistent band structure calculation for solid fcc He yields a linear relationship ΔE=C.n with Cth=22 × 10?3 eV nm3. Systematic electron energy loss spectroscopy and transmission electron microscopy studies of He bubbles in Al for various He doses and temperatures result in Cexp=(24±8).10?3 eV nm3 in agreement with theory. The analysis is consistent with the assumption that dislocation loop punching is the dominant bubble growth mechanism during high-dose room temperature implantation. The application to He bubbles in Ni indicates a maximum He density of n=0.2 × 103 nm?3 for which He should be solid at room temperature. 相似文献
Ketones 2 (MSDC-0160) and 3 (MSDC-0602) had been selected for clinical development, however their initial syntheses were considered suboptimal for application deep into clinical trials. Difficulties ranging from the nature of the starting material, alcohol oxidation problems, epoxide opening regioisomeric issues, and endgame ketone redox problems had been encountered. Direct ketone introduction/maintenance was desired for maximum efficiency and convergence was found to be critically dependent upon the acidity of the nucleophilic species (13, 18) and the use of pre- or post-alkylative oximino-ether/oxime protection (vide infra). Improvements in overall yield for the syntheses of 2 (MSDC-0160) and 3 (MSDC-0602) from 20% (2) and 31% (3) respectively, to 44% (2) and 59% (3) were realized. 相似文献
The energy barrier leading to magnetic bistability in molecular clusters is determined by the magnetic anisotropy of the cluster constituents. By incorporating a highly anisotropic four‐coordinate cobalt(II) building block into a strongly coupled fully air‐ and moisture‐stable three‐spin system, it proved possible to suppress under‐barrier Raman processes leading to 350‐fold increase of magnetization relaxation time and pronounced hysteresis. Relaxation times of up to 9 hours at low temperatures were found. 相似文献
This work reports the first compound containing both a tetrazole and an azasydnone ring, a unique energetic material. Several energetic salts of the tetrazole azasydnone were synthesized and characterized, leading to the creation of new secondary and primary explosives. Molecular structures are confirmed by 1H and 13C NMR, IR spectroscopy, and X-ray crystallographic analysis. The high heats of formation, fast detonation velocities, and straight-forward synthesis of energetic azasydnones should capture the attention of future energetics research. 相似文献
The crystal structure of butyllithium solvated by 1,2-dipiperidinoethane, BuLi·DPE-6, which has been used as an initiator
for a number of important commercial anionic polymerization reactions, is reported. The complex crystallizes from pentane
as a centrosymmetric dimer in the monoclinic space group P21/n with a = 9.8619(12), b = 17.963(2), c = 10.3655(12) ?, β = 114.090(2)° and Z = 2. The dimer is located on a crystallographic inversion center. The crystal under investigation was found to be non-merohedrally
twinned. In contrast to the two other dimeric BuLi complexes previously structurally characterized in the solid state, BuLi·DPE-6
has a planar central Li2C2 core. Semi-empirical (PM3) calculations were used to determine the lowest energy conformations of the dimer and also identified
three structural motifs that affect Li2C2 dimer ring planarity. 相似文献
A series of heterotrimetallic manganese-lanthanide-sodium dimer metallacrowns has been synthesized and characterized by single-crystal X-ray analysis: {LnNa[12-MCMn(III)N(shi)-4]}2(iph)4, where LnIII?=?La (1), Ce (2), Pr (3), Nd (4), Sm (5), Eu (6), Gd (7), Tb (8), Dy (9), Ho (10), Er (11), Tm (12), Yb (13), Lu (14), and Y (15); MC is metallacrown; shi3? is salicylhydroximate; and iph2? is isophthalate. The manganese(III) ions and shi3? ligands generate the 12-MC-4 framework with one LnIII and Na+ ion bound to each [12-MCMn(III)N(shi)-4] on opposite sides of the central MC cavity. The carboxylate groups of the isophthalate ligands bridge between the central LnIII ion and each ring MnIII ion, and the meta-arrangement of the carboxylate groups joins two LnNa[12-MCMn(III)N(shi)-4] units together to form the dimer through the LnIII ions, which reside on the interior of the molecule. The identity of the central LnIII ion slightly impacts the size the [12-MCMn(III)N(shi)-4] framework. As the crystal radius of the LnIII ion increases from LuIII (1.02 Å) to LaIII (1.19 Å), the 12-MC-4 framework expands to accommodate the larger LnIII ion as the MC cavity increases in size (0.53 Å for LuIII to 0.58 Å for LaIII) and the average cross cavity MnIII-MnIII and oxime oxygen-oxime oxygen distances also increase (MnIII-MnIII distances: 6.48 Å for LuIII to 6.52 Å for LaIII; Ooxime-Ooxime distances: 3.66 Å for LuIII to 3.75 Å for LaIII). In addition, the larger LnIII ions reside further from the MC cavity as indicated by the LnIII-oxime oxygen mean plane (OoxMP) distance. The LnIII-OoxMP distance steadily decreases from LaIII (1.7527(12) Å) to LuIII (1.5575(15) Å).
Graphic Abstract
The complex {LaNa[12-MCMn(III)N(shi)-4]}2(iph)4(DMF)6(H2O)2 is a dimer of [12-MC-4] molecules linked by four isophthalate anions
A series of Ru(II) and Ru(III) complexes of the types [RuX(CO)(EPh3)2L] (X = H, E = P; X = Cl, E = P or As) and [RuX2(EPh3)2L] (X = Cl, E = P or As; X = Br, E = As, L = monoanion of dehydroacetic acid) have been synthesized in order to explore their biological activities, such as DNA-binding and antibacterial activity. The complexes were characterized by analytical and spectroscopic techniques. The crystal and molecular structure of [RuCl2(AsPh3)2(L)] has been determined by single crystal XRD. The cyclic voltammograms of the complexes in acetonitrile displayed either quasi-reversible or irreversible redox couples based on the metal centre. The ligand, dehydroacetic acid (DHA) and its metal complexes were tested against five pathogenic bacteria. Absorption titration and cyclic voltammetric studies revealed that the complexes interact with Herring Sperm ds DNA through different binding modes to different extents. 相似文献
Absolute rate coefficients for the reaction between the important environmental free radical oxidant NO3. and a series of N‐ and C‐protected amino acids, di‐ and tripeptides were determined using 355 nm laser flash photolysis of cerium(IV) ammonium nitrate in the presence of the respective substrates in acetonitrile at 298±1 K. Through combination with computational studies it was revealed that the reaction with acyclic aliphatic amino acids proceeds through hydrogen abstraction from the α‐carbon, which is associated with a rate coefficient of about 1.8×106 m ?1 s?1 per abstractable hydrogen atom. The considerably faster reaction with phenylalanine [k=(1.1±0.1)×107 m ?1 s?1] is indicative for a mechanism involving electron transfer. An unprecedented amplification of the rate coefficient by a factor of 7–20 was found with di‐ and tripeptides that contain more than one phenylalanine residue. This suggests a synergistic effect between two aromatic rings in close vicinity, which makes such peptide sequences highly vulnerable to oxidative damage by this major environmental pollutant. 相似文献