聚乙烯亚胺-金属络合物的稳定常数及配位数的测定

将聚合物络合超滤(PC-UF)技术与电感耦合等离子体质谱(ICP-MS)结合, 利用化学理论计算模型, 建立了测定聚乙烯亚胺(PEI)与金属离子络合稳定常数及平均配位数的方法. 将该方法用于PEI与Cd²⁺的络合过程. 配制不同浓度比的PEI和Cd²⁺的混合溶液, 待络合反应平衡后, 用超滤离心管离心分离高分子PEI-Cd络合物, 自由离子Cd²⁺及其小分子络合物渗滤至滤液中; 用10 mL体积分数为3%稀硝酸将滤膜上截留的PEI-Cd络合物解离, 离心得到Cd²⁺的稀硝酸溶液; 用ICP-MS分别测定2次超滤后滤液中Cd²⁺的浓度, 利用化学理论模型进行计算, 得到PEI-Cd络合物的稳定常数和平均配位数. pH=4.0～5.9时, PEI-Cd络合平衡的研究结果表明, 稳定常数和平均配位数均随pH值的增大而增大, 较低程度的质子化可使PEI与Cd²⁺的络合能力增强, 络合稳定常数增大.     

二甲苯、卤代苯在硝酸银溶液中的溶解平衡

具有C＝C双键的许多有机化合物可与银离子形成络合物。L.J.Andrews和R.M.Kcefcr等用在含Ag⁺的芳烃溶液中测定溶解度的方法,计算了某些芳烃与Ag⁺络合物的形成常数^[1]。     

pH法研究UO2+2与甘氨酰替甘氨酸、白氨酸和四咪噻唑的络合物

本文应用pH法测定了UO₂⁺²与甘氨酰替甘氨酸、白氨酸和d,l-2,3,5,6-四氢-6-苯基咪唑[2,1-6]噻唑的络合物的逐级稳定常数,分别得出,UO₂⁺²-甘氨酰替甘氨酸体系:β₁=5.7×10³和β₂=1.4×10¹⁰;UO₂⁺²-白氨酸体系:β₁=4.0×10⁵和β₂=1.6×10¹³,以及UO₂⁺²-d,l-2,3,5,6-四氢-6-苯基咪唑(2,1-6)噻唑体系:β₁=6.5×10⁴和β₂=2.0×10¹⁰(25℃,μ=0.1,KCl维持)。同时,将徐光宪的溶液中络合物吸附平衡理论引入pH法研究络合物稳定常数中。     

冠醚过渡金属络合物的制备及振动光谱研究

本工作以12-冠-4、15-冠-5、18-冠-6为配体合成了过渡金属Cr³⁺、Fe³⁺、Mn²⁺、Co²⁺、Ni²⁺、CO²⁺的硝酸盐和氯化物两个系列的络合物,共26个对这26种络合物进行了红外、拉曼光谱的测定。光谱中,冠醚的OC-O-C伸缩振动、环弯曲、"环呼吸"振动以及CH₂面内摇摆振动在络合物形成后出现了规律性变化。     

稀土元素的电分析化学研究——Ⅱ.钪-氯化铵-铜铁试剂-二苯胍体系的络合吸附波机理的研究

在示波极谱上,在氯化铵底液中,pH4～7时,Sc³⁺-铜铁试剂(Cup)-二苯胍(DPG)体系产生一个较大的催化波,在1×l0^-7～1×l0^-6M Sc³⁺浓度内与波高有线性关系,而在dc极谱上不产生催化波.此波为络合吸附波,络合物在电极上的吸附平衡不能瞬时达到.络合物组成为:Sc³⁺:Cup:DPG:CL^-=1:1:1:2,它具有八面体构型.在实验条件下,条件稳定常数β=1.22×10⁷.四元络合离子吸附于电极表面,络合物中的Cup以酸形式在电极上还原,产物为苯肼;释出的Sc³⁺可以再络合、吸附,产生催化电流.     

pH电位法研究络合物稳定常数——一种新的数据处理方法的尝试

在水溶液的络合平衡研究中,pH电位法得到广泛应用,但有一定局限性。G·Shwarzenbach提出的pH-pM同时测定法原则上可以处理多级酸式络合常数,但实验受到仪器的限制。借助徐光宪^[4]的络合物吸附平衡理论可以将Y₀(Frouaeus函数)与n_L(生成函数)相联系,从而可能将上述两种方法沟通起来^[2]。但文献[2]所介绍的方法只适于求各级正常络合物常数。     

Ni2+-胆红素和Ni2+-2,2'联吡啶-胆红素的单扫描极谱研究

本文研究了Ni²⁺-胆红素和Ni²⁺-2,2'联吡啶-胆红素在微碱性介质中的单扫描极谱行为和电极反应机理.在Ni²⁺-胆红素体系中.于-1.0V处产生络合物的催化前波;而在Ni²⁺-2,2'联吡啶-胆红素体系中,则于-1.5V处产生催化氢波.这2个体系的线性范围分别为1×10^-6～5×10^-6mol/L和2×10^-7～8×10^-6mol/L.     

pH法测定若干金属离子与天门冬酰胺络合反应的热力学参数

本文在不同温度和离子强度为0.1的条件下,以pH电位法分别测定了Co²⁺、Ni²⁺、Cu²⁺、Zn²⁺、Cd²⁺与天门冬酰胺形成1:2络合物时的平衡常数。在所有测定的温度范围内,吉氏自由能变化的递变顺序为Cu²⁺2+2+2+2+。以温度系数法计算了有关络合反应的焓和墙的变化,并据此对反应的动力问题进行了讨论。     

可区别铁离子荧光探针异构体的合成及其水样分析

分别以2-（2-氨基苯基）菲并咪唑和2-（3-氨基苯基）菲并咪唑为原料,与5-硝基水杨醛反应合成了两个菲并咪唑-苯酚异构体衍生物（PI?o?OH和PI?m?OH）。在水相体系中（V（DMF）∶V（HEPES） = 1∶1,pH = 7.4）,两个异构体发射中等强度的荧光。Fe³⁺存在下,两个异构体的荧光强度分别淬灭为原来的1/3和1/6,淬灭常数为4.8×10³和4.6×10³ L/mol,且淬灭效果不受其它干扰离子和pH值变化的影响。间位异构体PI?m?OH与Fe³⁺的荧光识别在2 min之内完成,配合速度明显优于邻位基异构体,且配合稳定性高于邻位异构体,配合常数为3.82×10⁴ L/mol。通过高分辨质谱和Job's曲线,确定了两个异构体与Fe³⁺识别配合比为1∶1,并建议了PI?m?OH-Fe³⁺ and PI?o?OH-Fe³⁺两个配合物的结构。两个异构体均可实现实际水样中Fe³⁺的定量检测,表明它们在实际水样的Fe³⁺分析中具有一定的应用价值。     

双金属氰化络合物及其催化的聚合反应

本文综述了双金属氰化络合物及其催化的环氧化物参与的聚合反应研究。双金属氰化络合物是由其内界金属M^Ⅱ通过氰基与外界金属M^Ⅰ连接形成的含 M^Ⅱ-C≡N-M^Ⅰ 桥键的三维网络状无机高分子(M^Ⅰ一般为Zn²⁺、Fe²⁺、Co²⁺和Ni²⁺等二价金属离子,M^Ⅱ一般为Fe²⁺、Fe³⁺、Co²⁺、Co³⁺和Ni²⁺等过渡金属离子)。外界金属M^Ⅰ一般被认为是催化反应的活性中心金属。该类催化剂早期被用于催化环氧化物开环聚合,并逐步发展成为合成中高分子量、低不饱和度聚醚多元醇的极高效催化剂。近年来该类催化剂被用来催化环氧化物/环状酸酐共聚、环氧化物/CX₂(X≡O,S)共聚和环氧化物/环状酸酐/CO₂三元共聚反应合成聚酯、聚碳酸酯、聚(醚-碳酸酯)、聚硫代碳酸酯和聚(碳酸酯-酯)等具有生物降解性的聚合物。尤其对氧化环己烯(CHO)与CO₂(或酸酐)共聚,锌-钴双金属氰化络合物表现出了极高的催化活性和选择性。结合本研究组十多年的研究结果,本文讨论了双金属氰化络合物催化活性中心的可能结构和催化机理,提出了双金属氰化络合物催化聚合的共性难题和解决这些问题的方向。     

Computer generation of the characteristic polynomials of chemical graphs

A computer program based on the Frame method for the characteristic polynomials of graphs is developed. This program makes use of an efficient polynomial algorithm of Frame for generating the coefficients in the characteristic polynomials of graphs. This program requires as input only the set of vertices that are neighbors of a given vertex and with labels smaller than the label of that vertex. The program generates and stores only the lower triangle of the adjacency matrix in canonical ordering in a one-dimensional array. The program is written in integer arithmetic, and it can be easily modified to real arithmetic. The coefficients in the characteristic polynomials of several graphs were generated in less than a few seconds, thus solving the difficult problem of generating characteristic polynomials of graphs. The characteristic polynomials of a number of very complicated graphs are obtained including for the first time the characteristic polynomial of an honeycomb lattice graph containing 54 vertices.     

Yammp: Development of a molecular mechanics program using the modular programming method

Molecular mechanics is a fast developing discipline with new methods and potential fields appearing every year. A versatile molecular mechanics program supports many methods and potential fields that make it unavoidably large. There are problems writing and maintaining large programs with traditional methods because of data and other dependencies. Modular programming provides a solution. A program is developed as a collection of highly independent modules containing only related data structures and procedures. These entities are isolated in the module and access to them is provided through a well-defined and controlled interface. The high degree of independence circumscribes programming errors. Most of all, it reduces the cost of revising the program as only a small part of the program needs to be read and understood for each revision. We implemented a molecular mechanics program, yammp, using the modular programming method. © 1993 John Wiley & Sons, Inc.     

User-oriented software for determination of the precision of signal-integrating analytical methods

A software package for the determination of the uncertainty in signal-integrating analytical techniques is presented. The program can be used to calculate detection limits and to determine baseline drift properties, the influence of drift-correcting procedures and integration time, etc. Complete analytical procedures, e.g., chromatography or atomic emission spectrometry, or parts of a system can be tested. No profound theoretical knowledge is required by the user; confidence intervals are calculated where necessary. The theoretical basis and the structure of the program are evaluated.     

A quantitative method for following the precipitation of slightly soluble salts of polyprotic weak acids

A quantitative method of following the precipitation of slightly soluble salts of polyprotic weak acids is described; the method is based on a computer program designed to simulate the precipitation at constant pH. The program simulates the simultaneous formatioi of a number of precipitates of different composition which can be slightly soluble salts of the weak polyprotic acid H_nA (n ? 5) and/or hydroxides of the metallic cations of groups I, II and III of the periodic table, provided that the molar ratio of the ions involved is constant during precipitation and that hydrogen or hydroxyl ions are liberated in the process. The program takes into account the probability of the formation of soluble complexes of the type BH_n — _iA as well as metal hydroxo complexes.     

Vectorization of the general Monte Carlo classical trajectory program VENUS

The general chemical dynamics computer program VENUS is used to perform classical trajectory simulations for large polyatomic systems, with many atoms and complicated potential energy functions. To simulate an ensemble of many trajectories requires a large amount of CPU time. Since each trajectory is independent, it is possible to parallel process a large set of trajectories instead of processing the trajectories by the conventional sequential approach. This enhances the vectorizability of the VENUS program, since the integration of Hamilton's equations of motion and the gradient evaluation, which comprise 97.8% of the CPU, can each be parallel processed. In this article, the vectorization and ensuing optimization of VENUS on the CRAY-YMP and IBM-3090 are presented in terms of both global strategies and technical details. A switching algorithm is designed to enhance the vector performance and to minimize the memory storage. A performance of 140 MFLOPS and a vector/scalar execution rate ratio of 10.6 are observed when this new version of VENUS is used to study the association of CH₃ with the H(Ar)₁₂ cluster on the CRAY-YMP.     

Rapid grid-based construction of the molecular surface and the use of induced surface charge to calculate reaction field energies: applications to the molecular systems and geometric objects

This article describes a number of algorithms that are designed to improve both the efficiency and accuracy of finite difference solutions to the Poisson-Boltzmann equation (the FDPB method) and to extend its range of application. The algorithms are incorporated in the DelPhi program. The first algorithm involves an efficient and accurate semianalytical method to map the molecular surface of a molecule onto a three-dimensional lattice. This method constitutes a significant improvement over existing methods in terms of its combination of speed and accuracy. The DelPhi program has also been expanded to allow the definition of geometrical objects such as spheres, cylinders, cones, and parallelepipeds, which can be used to describe a system that may also include a standard atomic level depiction of molecules. Each object can have a different dielectric constant and a different surface or volume charge distribution. The improved definition of the surface leads to increased precision in the numerical solutions of the PB equation that are obtained. A further improvement in the precision of solvation energy calculations is obtained from a procedure that calculates induced surface charges from the FDPB solutions and then uses these charges in the calculation of reaction field energies. The program allows for finite difference grids of large dimension; currently a maximum of 571(3) can be used on molecules containing several thousand atoms and charges. As described elsewhere, DelPhi can also treat mixed salt systems containing mono- and divalent ions and provide electrostatic free energies as defined by the nonlinear PB equation.     

Diffusional Dynamics of Cytochrome cMolecules in the Presence of a Charged Surface

A new Brownian dynamics code was developed that is capable of computing trajectories of several spherical particles in the presence of a charged planar surface. The code takes into account electrostatic, van der Waals, and hydrodynamic interactions. In this work we describe the methods used in the program and show results from calculations for cytochrome cmolecules interacting with a negatively charged lipid bilayer. This system is of particular biological interest since these molecules play a major role as electron carriers, e.g., in photosynthesis. The shape and charge distribution of cytochrome cmolecules can be well approximated as spherical particles with an embedded monopole and dipole and can therefore easily be handled by the program. That level of approximation makes it possible to study large systems with many (up to 100) particles over time scales up to milliseconds, which would be computationally too expensive using detailed atomistic models.     

A Computer Program for the Evaluation of Non-isothermal Kinetic Parameters

A program for the evaluation of non-isothermal kinetic parameters is presented. The program allows evaluation of the kinetic parameters under constant heating rate or constant reaction rate conditions. The simulation of temperature vs. conversion curves is also possible. A regression method is included, which allows a discrimination between various conversion functions and also evaluation of the activation parameters. The program was tested with various simulated decomposition curves and the non-isothermal decomposition curves of calcium oxalate. The program is written in Visual BASIC 4.0 and can be run under Windows 95 ©.