ICP—AES法测定硼酸铝钇钕（NYAB）激光晶体中的Nd

应用ICP-AES法分析自倍频激光晶体(NYAB)样品中的Nd,在石墨坩埚中于500℃用NaOH熔融分解样品,方法的回收率为96%～105%,测定的相对标准偏差为1.42%,方法简便,可给出满意的分析结果。     

A Low‐Spin Three‐Coordinate Cobalt(I) Complex and Its Reactivity toward H2 and Silane

A three‐coordinate low‐spin cobalt(I) complex generated using a pincer ligand is presented. Since an empty orbital is sterically exposed at the site trans to the N donor of an acridane moiety, the cobalt(I) center accepts the coordination of various donors such as H₂ and PhSiH₃ revealing σ‐complex formation. At this low‐spin cobalt(I) site, homolysis of H–H and Si?H bonds preferentially occurs via bimolecular hydrogen atom transfer instead of two‐electron oxidative addition. When the resulting Co^II–H species was exposed to N₂, H₂ evolution readily occurs at ambient conditions. These results suggest single‐electron processes are favored at the structurally rigidified cobalt center.     

A nonclassical dihydrogen adduct of S = ½ Fe(I)

We have exploited the capacity of the "(SiP(iPr)(3))Fe(I)" scaffold to accommodate additional axial ligands and characterized the mononuclear S = ? H(2) adduct complex (SiP(iPr)(3))Fe(I)(H(2)). EPR and ENDOR data, in the context of X-ray structural results, revealed that this complex provides a highly unusual example of an open-shell metal complex that binds dihydrogen as a ligand. The H(2) ligand at 2 K dynamically reorients within the ligand-binding pocket, tunneling among the energy minima created by strong interactions with the three Fe-P bonds.     

Thioether sulfur oxygenation from O2 or H2O2 reactivity of copper complexes with tridentate N2Sthioether ligands

To model thioether-copper coordination chemistry including oxidative reactivity, such as occurs in the copper monooxygenases peptidylglycine -hydroxylating monooxygenase (PHM) and dopamine beta-hydroxylase (DbetaH), we have synthesized new tridentate N2S ligands LSEP and LSBz [LSEP = methyl(2-phenethylsulfanylpropyl)(2-pyridin-2-ylethyl)amine; LSBz = (2-benzylsulfanylpropyl)methyl(2-pyridin-2-ylethyl)amine)]. Both copper(I) and copper(II) complexes have been prepared, and their respective O2 and H2O2 chemistry has been studied. Under mild conditions, oxygenation of [(LSEP)CuI]+ (1a) and [(LSBz)CuI]+ (2a) leads to ligand sulfoxidation, thus exhibiting copper monooxygenase activity. A copper(II) complex of this sulfoxide ligand product, [(LSOEP)CuII(CH3OH)(OClO3)2], has been structurally characterized, demonstrating Cu-Osulfoxide ligation. The X-ray structure of [(LSEP)CuII(H2O)(OClO3)]+ (1b) and its solution UV-visible spectral properties [S-CuII LMCT band at 365 nm (MeCN solvent); epsilon = 4285 M-1 cm-1] indicate the thioether sulfur atom is bound to the cupric ion in both the solid (CuII-S distance: 2.31 A) and solution states. Reaction of 1b with H2O2 leads to sulfonation via the sulfoxide; excess hydrogen peroxide gives mostly sulfone product. These results may provide some insight into recent reports concerning protein methionine oxidation, showing the potential importance of copper-mediated oxidation processes in certain biological settings.     

Conformational Adaptation of β-Peptide Foldamers for the Formation of Metal–Peptide Frameworks

Metal-coordinated frameworks derived from small peptidic ligands have received much attention thanks to peptides’ vast structural and functional diversity. Various peptides with partial conformational preferences have been used to build metal–peptide frameworks, however, the use of conformationally constrained β-peptide foldamers has not been explored yet. Herein we report the first metal-coordination-mediated assembly of β-peptide foldamers with 12-helical folding propensity. The coordination of Ag⁺ to the terminal pyridyl moieties afforded a set of metal–peptide frameworks with unique entangled topologies. Interestingly, formation of the network structures was accompanied by notable conformational distortions of the foldamer ligands. As the first demonstration of new metal–peptide frameworks built from modular β-peptide foldamers, we anticipate that this work will be an important benchmark for further structural evolution and mechanistic investigation.     

A molecular pinwheel multicopper(I) cluster, [(L(S-))6Cu(I)13(S2-)2]3+ with mu4-sulfido, mu3-thiolato and nitrogen ligands

A copper(I) complex with new N2S thiol ligand transforms to a multicopper(I) cluster, [(L(S-))6Cu(I)13(S2-)2]3+ (1); its X-ray structure exhibiting mu4-sulfido and mu3-thiolato coordination is presented and compared to other cuprous thiolato/sulfido clusters including that observed in the copper enzyme nitrous oxide reductase.     

Numerical investigation into the dependence of the Allen–Cahn equation on the free energy

In this paper, we study a direct parallel-in-time (PinT) algorithm for first- and second-order time-dependent differential equations. We use a second-order boundary value method as the time integrator. Instead of solving the corresponding all-at-once system iteratively, we diagonalize the time discretization matrix B, which yields a direct parallel implementation across all time steps. A crucial issue of this methodology is how the condition number (denoted by Cond₂(V )) of the eigenvector matrix V of B behaves as n grows, where n is the number of time steps. A large condition number leads to large roundoff error in the diagonalization procedure, which could seriously pollute the numerical accuracy. Based on a novel connection between the characteristic equation and the Chebyshev polynomials, we present explicit formulas for V and V^− 1, by which we prove that Cond\(_{2}(V)=\mathcal {O}(n^{2})\). This implies that the diagonalization process is well-conditioned and the roundoff error only increases moderately as n grows, and thus, compared to other direct PinT algorithms, a much larger n can be used to yield satisfactory parallelism. A fast structure-exploiting algorithm is also designed for computing the spectral diagonalization of B. Numerical results on parallel machine are given to support our findings, where over 60 times speedup is achieved with 256 cores.

     

Temperature-responsive smart surfaces via rise-and-descent transition: Attachability,durability, and fast sweating

Smart surfaces containing thermo-responsive hydrogels have been investigated for several decades, but the development of mechanically durable and versatile surfaces that can undergo distinct property changes remains a challenging task. Herein, we prepare smart surfaces showing reversible changes in micro-scale roughness, which are attachable to various polymeric substrates. The hydrogel microphase located between silicone phases responsively rise and descend (volcanic-terrain-mimetic transition); as a result, the surface properties reversibly swing from those of the hydrophobic silicone-like ones to those of the wet hydrogel ones. The durability of these surfaces resembles that of silicone, while their fast water release characteristics allow the utilization of the studied materials in self-aligning and artificial sweating applications. The release of the drug molecules loaded into the hydrogel phase is controlled by varying the temperature and composite structure. Thus, the fabricated versatile surfaces utilizing the volume transition of thermo-responsive hydrogels can meet the requirements of various future applications.     

Discovery of EGFR selective 4,6-disubstituted pyrimidines from a combinatorial kinase-directed heterocycle library

The epidermal growth factor receptor (EGFR) tyrosine kinase was one of the first receptor tyrosine kinases to be targeted for drug development by the pharmaceutical industry due to its ubiquitous overexpression in a variety of tumors. Despite the validation of several quinazoline-based scaffolds in the clinic, there is a dearth of alternative chemical structure classes that are capable of inhibiting EGFR kinase activity selectively. Here we describe the discovery of potent and highly selective 4,6-disubstituted pyrimidine inhibitors of enzymatic and cellular EGFR activity and provide an explanation for their exceptional degree of kinase selectivity.