Four divalent metal thiocyanate coordination compounds containing a rigid functional pyridine ligand

A series of new coordination compounds Zn(SCN)₂L₂ (1), Co(SCN)₂L₂ (2), [Cd(SCN)₂L₂·2L]_n (3) and [CdHg(SCN)₄L₂]_n (4) have been prepared by self-assembly of a rigid functional pyridine ligand, trans-4-[4′-(N-methyl-N-hydroxyethyl)amimo]styryl pyridine (abbreviated as L) with M(SCN)_x (M: Zn, Co, Cd, CdHg; x: 2, 4). The crystal structures indicate that 1 and 2 are mononuclear compounds while 3 and 4 are coordination polymers. O–H?N, C–H?O, O–H?π and C–H?π hydrogen bonds play significant roles in the final crystal structures. The solid-state luminescence properties have been measured. The results indicate that the photoluminescence spectra of all the compounds can be changed by the frameworks and introducing of different metal ions.     

丁二酸二异辛酯磺酸钠(AOT)/TritonX-100混合反胶束体系中纤维素酶降解纤维素的研究

对于底物不溶于水的纤维素降解反应而言,为了增强纤维素酶的活性,在丁二酸二异辛酯磺酸钠(AOT)/异辛烷反胶束体系中加入非离子表面活性剂TritonX-100进行纤维素降解实验.结果表明,在AOT中加入非离子表面活性剂TritonX-100可以使纤维素酶的活性提高,非离子表面活性剂TritonX-100与AOT的最佳物质的量之比是0.20.考察了水与表面活性剂的物质的量之比(Wo)、不同酸度(pH)和不同温度(T)等其他反应条件对纤维素降解反应的影响.研究结果表明,反应的最佳条件是:Wo为3.3,T为315.11K,pH为5.10.     

水合邻苯二甲酸钠的合成、结构表征及热化学性质

选择邻苯二甲酸和氢氧化钠作为反应物,利用液相合成方法合成了水合邻苯二甲酸钠.利用X射线粉末衍射、化学与元素分析等方法表征了它的组成和结构.利用精密自动绝热热量计测定了该化合物在78～366K温区的摩尔热容.将该温区的摩尔热容实验值用最小二乘法拟合得到摩尔热容(Cp,m)对温度(T)的多项式方程,用此方程进行数值积分得到此温度区间内每隔5K的舒平热容值和相对于298.15K时的热力学函数值.另外,依据Hess定律,通过设计合理的热化学循环,利用等温环境溶解-反应热量计分别测量了固相量热反应的反应物和产物在所选溶剂中的溶解焓,从而确定反应的反应焓为:ΔrHm=29.073±1.05kJ·mol-1.最后,利用反应的反应焓和其它反应物和产物已知的热力学数据计算出水合邻苯二甲酸钠的标准摩尔生成焓为:-1493.637±1.11kJ·mol-1.     

A practical strategy for the characterization of coumarins in Radix Glehniae by liquid chromatography coupled with triple quadrupole-linear ion trap mass spectrometry

The aim of the present study was to develop a practical method for the characterization of coumarins in Radix Glehniae by liquid chromatography–mass spectrometry (LC–MS). First, 10 coumarin standards (including two pairs of isomers) were studied, and mass spectrometry fragmentation patterns and elution time rules for the coumarins were found. Then, an extract of Radix Glehniae was analyzed by the combination of two scan modes, i.e., multiple ion monitoring-information-dependent acquisition-enhanced product ion mode (MIM-IDA-EPI) and precursor scan information-dependent acquisition-enhanced product ion mode (PREC-IDA-EPI) on a hybrid triple quadrupole-linear ion trap mass spectrometer. A total of 41 coumarins were identified on the basis of their mass spectrometry fragmentation patterns. This is the first time that these two scan modes have been combined to characterize chemical constituents in traditional Chinese medicine. This new method allowed the identification of coumarins in Radix Glehniae in trace amounts. The methodology proposed in this study could be valuable for the structural characterization of coumarins from complex natural and synthetic sources.     

Direct electrochemistry of myoglobin immobilized on chitosan-wrapped rod-constructed ZnO microspheres and its application to hydrogen peroxide biosensing

Rod-constructed zinc oxide (ZnO) microspheres (RZnOMs), consisting of hundreds of needle-like ZnO nanorods, were utilized to explore a novel biosensor through coupling with myoglobin (Mb) in the presence of chitosan (Chi). Biocompatibility and electrochemical properties of the resulting ZnO-Chi-Mb composite film were studied by Fourier-transform infrared spectroscopy and cyclic voltammetry. The results revealed that the RZnOMs-based composite was a satisfying matrix for proteins to effectively retain their native structure and bioactivity. With advantages of the unique inorganic material, facilitated direct electron transfer of the metalloenzymes was acquired on the RZnOMs-based enzyme electrode. Moreover, the RZnOMs-based biosensor also displayed significant electrocatalytic activity for the reduction of hydrogen peroxide with an apparent Michaelis–Menten constant (32 μM), wide linear range (2–490 μM), and low detection limit (0.21 μM, S/N = 3). These indicated that the RZnOMs were one of the ideal candidate materials for direct electrochemistry of redox proteins and related biosensor construction.     

Supramolecular networks of polymethylphosphonic acid groups bonded to aromatic platforms: biphenyldiyl-2,2'-bis(methylphosphonic acid) and benzenetriyl-1,3,5-tris(methylphosphonic acid)

Biphenyldiyl-2,2'-bis(methylphosphonic acid) (BBMP) and benzenetriyl-1,3,5-tris(methylphosphonic acid) (BTMP) as ligands have been synthesized from diphenic acid and trimesic acid, respectively. Cu, Mn and Co complexes of BBMP have been prepared but similar complexes of BTMP did not crystallize. However, a copper compound with added 4,4'-bipyridyl was obtained. This copper complex is dimeric in which the dimers are linked into a supramolecular compound through the bipyridyl groups. Interestingly, the structure was solved in P1 with an unusual correlation between the ligand oxygen bond distances and the copper bond distances to water molecules. The Mn and Co BBMP complexes are isostructural in which the BBMP ligands phenyl groups rotate around each other to bridge the metal atoms forming 1:1 linear chains. There are four water molecules bonded to Co that can be removed reversibly. In the case of the Cu compound, one Cu is square planar bonded to four phosphonate oxygen atoms from two BBMP molecules. The second copper is six coordinate adding two water molecules in the axial positions. The two copper ions alternate forming a one dimensional chain but with ligands bonding the chain on both sides. The four coordinate copper atoms are chelated by two BBMP ligands utilizing one oxygen atom from the two phosphonate groups of each ligand and a second oxygen atom from these groups that bridge across the Cu atoms to bond to the six coordinate copper ion. A detailed synthetic procedure for each of the two ligands is supplied as ESI.     

Spatiotemporal Kinetics in Solution Studied by Time‐Resolved X‐Ray Liquidography (Solution Scattering)

Information about temporally varying molecular structure during chemical processes is crucial for understanding the mechanism and function of a chemical reaction. Using ultrashort optical pulses to trigger a reaction in solution and using time‐resolved X‐ray diffraction (scattering) to interrogate the structural changes in the molecules, time‐resolved X‐ray liquidography (TRXL) is a direct tool for probing structural dynamics for chemical reactions in solution. TRXL can provide direct structural information that is difficult to extract from ultrafast optical spectroscopy, such as the time dependence of bond lengths and angles of all molecular species including short‐lived intermediates over a wide range of times, from picoseconds to milliseconds. TRXL elegantly complements ultrafast optical spectroscopy because the diffraction signals are sensitive to all chemical species simultaneously and the diffraction signal from each chemical species can be quantitatively calculated from its three‐dimensional atomic coordinates and compared with experimental TRXL data. Since X‐rays scatter from all the atoms in the solution sample, solutes as well as the solvent, the analysis of TRXL data can provide the temporal behavior of the solvent as well as the structural progression of all the solute molecules in all the reaction pathways, thus providing a global picture of the reactions and accurate branching ratios between multiple reaction pathways. The arrangement of the solvent around the solute molecule can also be extracted. This review summarizes recent developments in TRXL, including technical innovations in synchrotron beamlines and theoretical analysis of TRXL data, as well as several examples from simple molecules to an organometallic complex, nanoparticles, and proteins in solution. Future potential applications of TRXL in femtosecond studies and biologically relevant molecules are also briefly mentioned.     

Formation of singularities in the motion of plane curves under hyperbolic mean curvature flow

This paper concerns the hyperbolic mean curvature flow (HMCF) for plane curves. A quasilinear wave equation is derived and studied for the motion of plane curves under the HMCF. Based on this, we investigate the formation of singularities in the motion of these curves. In particular, we prove that the motion under the HMCF of periodic plane curves with small variation on one period and small initial velocity in general blows up and singularities develop in finite time. Some blowup results have been obtained and the estimates on the life-span of the solutions are given.     

Large deviation results for generalized compound negative binomial risk models

In this paper we extend and improve some results of the large deviation for random sums of random variables. Let {Xn;n 〉 1} be a sequence of non-negative, independent and identically distributed random variables with common heavy-tailed distribution function F and finite mean μ ∈R^＋, {N（n）; n ≥0} be a sequence of negative binomial distributed random variables with a parameter p C （0, 1）, n ≥ 0, let {M（n）; n ≥ 0} be a Poisson process with intensity λ 〉 0. Suppose {N（n）; n ≥ 0}, {Xn; n≥1} and {M（n）; n ≥ 0} are mutually independent. Write S（n） =N（n）∑i=1 Xi-cM（n）.Under the assumption F ∈ C, we prove some large deviation results. These results can be applied to certain problems in insurance and finance.     

捕食模型正周期解存在性的一个注记

利用重合度理论中的延拓定理讨论了多滞量捕食模型(dN_1(t))/dt=N_1(t)[r_1(t)-a_(11)(t)N_1(t-τ_1(t))-a_(12)(t)N_2(t-τ_2(t))] (dN_2(t))/dt=N_2(t)[-r_2(t)+a_(21)(t)N_1(t-τ_3(t))]的正周期解的存在性,得到了保证上述系统周期解存在的一组时滞依赖的充分条件,补充和完善了已有学者的工作.