溶剂化金属原子浸渍法制备高分散负载型催化剂——Ⅸ.K-Fe/硅沸石催化剂的XRD、TEM、XPS和磁测定表征

用溶剂化金属原子浸渍(SMAI)法和普通浸渍(CI)法两种不同的方法制备了组成相同的K-Fe/硅沸石催化剂。TEM,XRD,XPS和磁测定结果表明,SMAI K-Fe/硅沸有催化剂中铁的分散度和还原度都大于CI催化剂,SMAI催化剂中金属颗粒直径小于4nm,具有超顺磁性,而CI催化剂中金属颗粒较大,表现铁磁性。两种方法制备的催化剂反应前后金属的状态发生明显的改变,对CO+H_2反应的催化性质不同。     

对称三唑Schif碱和氯化铜配合物的研究

本文介绍水 杨醛与４－氨基－３，５－二乙基－１，２，４－三唑缩合而成对称三唑Ｓｃｈｉｆｆ碱与氯化铜形成一种新的配合物Ｃｕ（ＳＡＥＴＺ）２（ＳＡＥＴＺ＝４－（邻羟苯基亚甲基）－亚胺－３，５－二乙基－１，２，４－三唑）。     

The stabilization of arginine's zwitterion by dipole-binding of an excess electron

The arginine parent anion was generated by a newly developed, infrared desorption-electron photoemission hybrid anion source. The photoelectron spectrum of the arginine anion was recorded and interpreted as being due to dipole binding of the excess electron. The results are consistent with calculations by Rak, Skurski, Simons, and Gutowski, who predicted the near degeneracy of arginine's canonical and zwitterionic dipole bound anions. Since neutral arginine's zwitterion is slightly less stable than its canonical form, this work also demonstrates the ability of an excess electron to stabilize a zwitterion, just as ions and solvent molecules are already known to do.     

Vibrational population of H 2 + after electroionization of thermal H2

In an ion trap experiment we have determined the vibrational population of the lowest 9 vibrational levels of H ₂ ⁺ . We used photodissociation of the trapped molecules by 248 nm light from an excimer laser and the dependence of the photodissociation cross section from the vibrational state. Our results are in good agreement to calculations, which are based on the Franck-Condon principle, but include a variation of the internuclear distance in the transition matrix element.     

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??In this paper, we introduce a class of stochastic age-dependent population equations with Poisson jumps. Existence and uniqueness of energy solutions for stochastic age-dependent population dynamic system are proved under local non-Lipschitz condition in Hilbert space.     

β-Arylation of Racemic Secondary Benzylic Alcohols to Access Enantioenriched β-Arylated Alcohols

The transformation of alcohols into value-added products is of great importance, as simple alcohols are widespread and can be easily derived from both fossil fuels and biomass. The selective functionalization of a sp³ C−H bond on the alkyl side chain of an alcohol over its hydroxyl group would offer an expedient route to expand the chemical space of alcohols but it remains a challenging task. Harnessing the borrowing hydrogen strategy, the β-arylation of secondary alcohols with aryl bromides has been achieved in this study, which allows for the selective functionalization of a β-Csp³−H bond in an alcohol substrate. Under the catalysis of a Pd complex, secondary alcohols reacted with aryl bromides to afford 1,2-diaryl alcohols with broad substrate scope in the presence of a ketone additive. Furthermore, the enantioconvergent version of the reaction has also been realized, transforming racemic secondary alcohols into enantioenriched chiral 1,2-diaryl alcohols under the cooperative Pd and Ru catalysis. Mechanism studies indicate that the reactions are enabled by borrowing hydrogen catalysis.     

pH-responsive protein microcapsules fabricated via glutaraldehyde mediated covalent layer-by-layer assembly

Bovine serum albumin (BSA) hollow microcapsules were fabricated through glutaraldehyde (GA) mediated covalent layer-by-layer assembly. The GA cross-linking of the adsorbed BSA on the colloidal particles enabled their surfaces to be covered by reactive aldehyde groups, which reacted with BSA molecules to result in another covalently linked layer. Repeating of this cycle could then yield particles coated with BSA multilayers. Hollow microcapsules well dispersed in water were obtained after core removal. The good integrity and morphology of the BSA capsules were confirmed and characterized by confocal laser scanning microscopy, scanning electron microscopy and scanning force microscopy. The obtained BSA microcapsules possess reversible pH response, i.e., the capsules are permeable to macromolecules below pH 4 or above pH 10, while impermeable in between. The mechanisms of permeability transition were discussed. Using this property, dextran, with a molecular weight of ~155 kDa, was successfully loaded.     

Concise assembly of highly substituted furan-fused 1,4-thiazepines and their Diels-Alder reactions with benzynes

A facile and highly efficient three-component reaction of thiazole or benzothiazole carbenes, disubstituted ketenes, and activated alkynes is disclosed. With this methodology, a polysubstituted ring system containing furo[2,3-c]thiazepine core can be constructed from simple and readily accessible starting materials in good yields. The scope and limitation of this transformation were investigated in detail by using various thiazole carbene, ketene, and alkyne components. Furthermore, the synthetic utilities of these unique polyheterocyclic compounds were demonstrated via their Diels-Alder reactions with benzynes to furnish thiazepine-fused 7-oxanorbornadiene derivatives in excellent yields.     

Theoretical investigation on the detailed mechanism of the OH‐initiated atmospheric photooxidation of o‐xylene

The reaction mechanism for o‐xylene with OH radical and O₂ was studied by density functional theory (DFT) method. The geometries of the reactants, intermediates, transition states, and products were optimized at B3LYP/6‐31G(d,p) level. The corresponding vibration frequencies were calculated at the same level. The single‐point calculations for all the stationary points were carried out at the B3LYP/6‐311++G(2df,2pd) level using the B3LYP/6‐31G(d,p) optimized geometries. Reaction energies for the formation of the aromatic intermediate radicals have been obtained to determine their relative stability and reversibility, and their activation barriers have been analyzed to assess the energetically favorable pathways to propagate the o‐xylene oxidation. The results of the theoretical study indicate that OH addition to o‐xylene forms ipso, meta, and para isomers of o‐xylene‐OH adducts, and the ipso o‐xylene adduct is the most stable among these isomers. Oxygen is expected to add to the o‐xylene‐OH adducts forming o‐xylene peroxy radicals. And subsequent ring closure of the peroxyl radicals to form bicyclic radicals. With relatively low barriers, isomerization of the o‐xylene bicyclic radicals to more stable epoxide radicals likely occurs, competing with O₂ addition to form bicyclic peroxy radicals. The study provides thermochemical data for assessment of the photochemical production potential of ozone and formation of toxic products and secondary organic aerosol from o‐xylene photooxidation. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2008     

Electronic structure differences in ZrO2 vs HfO2

Although ZrO2 and HfO2 are, for the most part, quite similar chemically, subtle differences in their electronic structures appear to be responsible for differing MO2/Si (M = Zr, Hf) interface stabilities. To shed light on the electronic structure differences between ZrO2 and HfO2, we have conducted joint experimental and theoretical studies. Because molecular electron affinities are a sensitive probe of electronic structure, we have measured them by conducting photoelectron spectroscopic experiments on ZrO2(-) and HfO2(-). The adiabatic electron affinity of HfO2 was determined to be 2.14 +/- 0.03 eV, and that of ZrO2 was determined to be 1.64 +/- 0.03 eV. Concurrently, advanced electronic structure calculations were conducted to determine electron affinities, vibrational frequencies, and geometries of these systems. The calculated CCSD(T) electron affinities of HfO2 and ZrO2 were found to be 2.05 and 1.62 eV, respectively. The molecular results confirm earlier predictions from solid state calculations that HfO2 is more ionic than ZrO2. The excess electron in MO2(-) occupies an sd-type hybrid orbital localized on the M atom (M = Zr, Hf). The structural parameters of ZrO2 and HfO2 and their vibrational frequencies were found to be very similar. Upon the excess electron attachment, the M-O bond length increases by ca. 0.04 A, the OMO angle increases by 2-4 degrees, and frequencies of all vibrational modes become smaller, with the stretching modes being shifted by 30-50 cm(-1) and the bending mode by 15-25 cm(-1). Together, these studies unveil significant differences in the electronic structures of ZrO2 and HfO2 but not in their structural or vibrational characteristics.