Organotransition-Metal Complexes of Multidentate Ligands 6. Electronic and Steric Influences on the Formation of η2-Acyl Complexes

Three new η²-acyl complexes, TMo(CO)₂(η²-COR) (T = Tp', Tp'; R= Me, Buⁿ; Tp' = hydridotris(3,5-dimethyl-pyrazol-1-yl)borate; Tp' = hydridotris(3,4,5-trimethylpyrazol-l-yl)borate) prepared from the corresponding alkyl iodides, RI, and the anions, TMo(CO)^?₃. The preparation of Et₄N⁺Tp Mo(CO)₃^? is also described. Using solution IR spectra to monitor the reactions between RI and TMo(CO)₃^?, it was found that Tp'Mo(CO)₂(η²-COMe) was formed more readily than Tp'Mo(CO)₂(η²-COMe) which was obtained more easily than Tp'Mo(CO)₂(η²-COBuⁿ). This finding suggests that the mechanism is probably an ionic substitution rather than a radical mechanism. The different times required for the complete conversion from the anions to TMo(CO)₂(η²-COR) is rationalized in terms of the electronic and steric influences of T and RI.     

A pH-responsive ultrathin Cu-based nanoplatform for specific photothermal and chemodynamic synergistic therapy

Noninvasive tumor therapy requires a new generation of bionanomaterials towards sensitive response to the unique tumor microenvironment to achieve accurate and effective treatment. Herein, we have developed a tumor therapy nanoplatform by immobilizing natural glucose oxidase (GOD) onto Cu-based layered double hydroxide (CuFe-LDH) nanosheets, which for the first time integrates acid-enhanced photothermal therapy (PTT), and pH-responsive and heat-facilitated chemodynamic therapy (CDT) simultaneously. As demonstrated by EXAFS and HRTEM, CuFe-LDH nanosheets possess a considerable number of defects caused by different acid conditions, resulting in a significantly acid-enhanced photothermal conversion efficiency (83.2% at pH 5.4 vs. 46.0% at pH 7.4). Moreover, GOD/CuFe-LDH nanosheets can convert a cascade of glucose into hydroxyl radicals (˙OH) under tumor acid conditions, which is validated by a high maximum velocity (V_max = 2.00 × 10⁻⁷ M) and low Michaelis–Menten constant (K_M = 12.01 mM). With the combination of PTT and CDT, the tumor tissue in vivo is almost eliminated with low-dose drug injection (1 mg kg⁻¹). Therefore, this novel pH-responsive Cu-based nanoplatform holds great promise in tumor-specific CDT/PTT synergistic therapy.

A pH-responsive multifunctional nanosystem was synthesized by loading glucose oxidase (GOD) onto CuFe-layered double hydroxide (LDH) nanosheets, which exhibited synchronous acid-enhanced/responsive photothermal and chemodynamic synergistic therapy.     

Synthesis and application of diphenylbis (3,5-dimethylpyrazol-1-yl)methane to form η-arene complexes of molybdenum

The neutral nitrogen-bidentate ligand, diphenylbis(3,5-dimethylpyrazol-1-yl)methane, Ph₂CPz′₂, can readily be obtained by the reaction of Ph₂CCl₂ with excess HPz′ in a mixed-solvent system of toluene and triethylamine. It reacts with [Mo(CO)₆] in 1,2-dimethoxyethane to give the η²-arene complex, [Mo(Ph₂CPz′₂)(CO)₃] (1). This η²-ligation appears to stabilize the coordination of Ph₂CPz′ ₂ in forming [Mo(Ph₂CPz′₂)(CO)₂(N₂C₆H₄NO₂-p)][BPh₄] (2) and [Mo(Ph₂CPz′₂)(CO)₂(N₂Ph)] [BF₄] (3) from the reaction of 1 with the appropriate diazonium salt but the stabilization seems not strong enough when [Mo{P(OMe)₃} ₃(CO)₃] is formed from the reaction of 1 with P(OMe)₃. The solid-state structures of 1 and 3 have been determined by X-ray crystallography: 1-CH₂Cl₂, monoclinic, P2₁/n, a = 11.814(3), b = 11.7929(12), c = 19.46 0(6) Å, β = 95.605(24)°, V = 2698.2(11) ų, Z = 4, D_calc = 1.530 g/cm³ , R = 0.044, R_w = 0.036 based on 3218 reflections with I > 2σ(I); 2 (3)-1/2 hexane-1/2 CH₃OH-1/2 H₂O-1 CH₂Cl₂, monoclinic, C2/c, a = 41.766(10), b = 20.518(4), c = 16.784(3) Å, β = 101.871(18)°, V = 14076(5) ų, Z = 8, D_calc = 1.457 g/cm³, R = 0.064, R_w = 0.059 based on 5865 reflections with I > 2σ(I). Two independent cations were found in the asymmetric unit of the crystals of 3. The average distance between the Mo and the two η²-ligated carbon atoms is 2.574 Å in 1 and 2.581 and 2.608 Å in 3. The unfavourable disposition of the η²-phenyl group with respect to the metal centre in 3 and the rigidity of the η²-arene ligation excludes the possibility of any appreciable agostic C---H → Mo interaction.     

Tandem mass spectrometric strategies for determination of sulfation positions and uronic acid epimerization in chondroitin sulfate oligosaccharides

Chondroitin sulfate (CS) is a glycosaminoglycan consisting of repeating (HexA-GalNAc sulfate) disaccharides, the functions of which depend on patterns of sulfation and uronic acid epimerization. The correlation of biological activities with structure requires a strategy to determine the sequences of CS oligosaccharides without the need for total isolation. Tandem mass spectrometry has enabled the development of proteomics, based on CID fragmentation of ions produced from complex mixtures of proteolytic peptides, and has the potential for rapid sequencing of CS and other glycosaminoglycan classes. The most challenging aspects of CS sequencing are to distinguish GalNAc residues sulfated at the 4- versus the 6-position and uronic acid epimers. This work describes the utility of (1) reducing terminal derivatives and (2) control of precursor ion charge state for tandem mass spectrometric strategies for determining GalNAc sulfation positional isomers of CS. The capability of tandem MS to differentiate uronic acid epimers is also shown, providing evidence that complete or nearly complete information on CS covalent structure may be obtained using tandem MS.     

Six new 2-(2-phenylethyl)chromones from Agarwood

Six new chromones, 6-methoxy-2-[2-(3-methoxy-4-hydroxyphenyl)ethyllchromone (2), 6,8-dihydroxy-2-(2-phenylethyl)chromone (3), 6-hydroxy-2-[2-(4-hydroxyphenyl)ethyl]chromone (4), 6-hydroxy-2-[2-(2-hydroxyphenyl)ethyl]chromone (5), 7-hydroxy-2-(2-phenylethyl)chromone (6), and 6-hydroxy-7-methoxy-2-(2-phenylethyl)chromone (7) were isolated from the ether extract of agarwood in addition to a known compound, 2-(2-phenylethyl)chromone or flidersiachromone (1). Their structures were determined by spectroscopic methods including UV, IR, and NMR spectral data and comparisons with the calculated values using the hydroxyl and methoxyl substituent increments of the chromone ring.     

色散缓变光纤中皮秒孤子脉冲的压缩

本文实验研究了孤子脉冲在色散缓变光纤中传输时的动力学特性,发现孤子脉冲在色散缓变光纤中能被压缩.采用500米色散缓变光纤,成功将4.4ps的孤子脉冲压缩到830fs,脉冲压缩比为5.3.色散缓变光纤中孤子脉冲压缩的实验研究为超短光脉冲压缩提供了新的途径和方法.     

A complete characterization for <Emphasis Type="Italic">k</Emphasis>-resonant Klein-bottle polyhexes

A hexagonal tessellation K(p, q, t) on Klein bottle, a non-orientable surface with cross-cap number 2, is a finite-sized elemental benzenoid which can be produced from a p × q-parallelogram of hexagonal lattice with usual identifications of sides and with torsion t. Unlike torus, Klein bottle polyhex K(p, q, t) is not transitive except for some degenerated cases. We shall show, however, that K(p, q, t) does not depend on t. Accordingly, criteria for K(p, q, t) to be k-resonant for every positive integer k will be given. Moreover, we shall show that K(3, q, t) of 3-resonance are fully-benzenoid.      

叶绿素a分子在乙醇溶剂中的瞬态吸收研究

The excited state of Chlorophyll a is investigated by femtosecond transient absorption. The transient absorption spectra of Q band and By band of Chlorophyll a in ethanol have been observed. The fast kinetics of Chlorophyll a which exhibit two ultrafast components were also measured. The one is assigned to transient absorption of the inhomogeneously broadened ground state absorption spectrum, while the other is the response of the solvent to the change of the electron configuration in the excited state due to salvation dynamics of the polar solvent molecules. To understand the anisotropy of Chlorophyll a in ethanol, the anisotropy profile was also performed by 405 nm excitation and found that the anisotropy profile is 0.143. The possible combination of θda, θdb and η at excitation of By band has been simulated.     

A Thermodynamic Analysis on the Catalytic Combustion of Methane

Chemical equilibria involving 10 species and adiabatic reaction temperature of methane com-bustion in air under various conditions have been calculated in detail by means of total Gibbs energyminimization of the system. The calculation data show that the adiabatic combustion temperature of CH_4and air at stoichiometric ratio is up to about 2200 K, and the equilibrium concentration of NO is about0.0018, however that of NO_2 is only 1×10~(-6). A large amount of carbon deposition emerges when the CH_4concentration is above 26.5%. The NO and NO_2 appear only when the CH_4 concentration is below 16%.The maximum equilibrium concentrations of NO and NO_2 are 0.0028 and 2×10~(-6) respectively, at about8%CH_4 concentration. The NO and NO_2 concentrations increase with the system temperature at a lowCH_4 concentration. However, both of them can be decreased when CO_2 or steam is introduced into thesystem, which also decreases the adiabatic combustion temperature. The decrease in adiabatic tempera-ture caused by     

An approach to analysis of single pier based on the variational principle in multi-layered soil

In this study, a variational approach to the settlement analysis of an axially loaded pier embedded in a multi-layered soil profile is presented. In this method, the soil profile and the embedded pier are divided into a number of sub-layers according to the actual number of soil layers observed in the field. The displacement shape function of each soil layer is given as a product of an exponential equation along the pier depth and the Bessel's solution in the radial direction. The displacement relationship among the layers can be derived through the transformation matrices. One of the major features of this method is that the total number of pier elements is the same as that of soil sub-layers. All the field components, such as the displacement, stress, and strain in the soil, can be calculated by closed-form solutions except that the only unknown variable is the value β which can be determined by iteration techniques. Comparisons were made with the results of finite element analysis and the field observation in pile-loaded tests.