Dynamics of Electrons in Ammonia Cages: The Discovery System of Solvation

Two centuries ago solvated electrons were discovered in liquid ammonia and a century later the concept of the solvent cage was introduced. Here, we report a real time study of the dynamics of size‐selected clusters, n=20 to 60, of electrons in ammonia, and, for comparison, that of electrons in water cages. Unlike the water case, the observed dynamics for ammonia indicates the formation, through a 100 fs temperature jump, of a solvent collective motion in a 500 fs relaxation process. The agreement of the experimental results—obtained for a well‐defined n, gated electron kinetic energy, and time delay—with molecular dynamics theory suggests the critical and different role of the kinetic energy and the librational motions involved in solvation.     

Sequential transduction of light into redox and acid—base energy in photosynthesis

Photosynthesis consists essentially in the conversion, by the plant kingdom, of sunlight energy into chemical energy (cell material and molecular oxygen). From a physicochemical point of view, photosynthesis is intrinsically a light-driven oxidation—reduction/acid—base process. In the course of photosynthesis, water is oxidized to molecular oxygen, whereas carbon dioxide, nitrate or dinitrogen, and sulfate are respectively reduced to carbohydrate, ammonia and sulfide; water is moreover ionized, in similar amounts, into protons and hydroxide anions. Phosphorus does not change its oxidation state, but orthophosphate becomes energized to metaphosphate, at the expense of the ionization products of water, in a peculiar acid—base process. Metaphosphate is mostly used as an energy shuttle in many cell processes, among them in the reduction and assimilation of the primordial bioelements, as well as in the polymerization of the resulting monomers — sugars, lipid components, amino acids, nucleotides — and deenergizes itself back to orthophosphate, again in acid—base reactions. The role of the oxide anion, that is, an oxygen atom with two additional electrons, O²⁻ , in these bioenergetic processes is especially discussed.     

2,2’-二甲基-4,4’-联噻唑与CHCl3分子间相互作用的理论研究

采用量子化学从头算理论在MP2/6-31G(d,p)水平上对2,2’-二甲基-4,4’-联噻唑顺反异构体, trans-2,2’-二甲基-4,4’-联噻唑-CHCl3 (I), cis-2,2’-二甲基-4,4’-联噻唑-CHCl3 (II)形成的1∶1氢键复合物进行计算研究. 结果表明, 2,2’-二甲基-4,4’-联噻唑在气相条件下, 反式构象比顺式构象稳定. 氯仿与2,2’-二甲基-4,4’-联噻唑形成的复合物存在较强的氢键, 表现为氮原子的孤对电子与氯仿分子中C—H反键σ轨道的相互作用, 另外形成C—H…Cl弱相互作用, 氢键作用使2,2’-二甲基-4,4’-联噻唑的顺式结构在氯仿溶剂比反式结构更稳定.     

The structure of the nickel—8-quinolinol complex in some organic solvents

The ultraviolet and visible absorption spectra of the nickel—8-quinolinol complex in chloroform are significantly affected by traces of water. Absorption spectra of the complex in mixed solvents, e.g. dioxane—water, dioxane—methanol and chloroform-methanol, and in chloroform solution containing water, pyridine, or 8-quinolinol are compared. An addition compound is formed in which the mole ratio of the nickel-8-quinolinol complex to the solvent or the base is 1:1 or 1:2. Polymerization occurs by mutual interaction between the nickel-8-quinolinol complexes. A degree of polymerization of 2.2 was obtained; this indicates that the binuclear compound predominates. The structure of the nickel—8-quinolinol complex in organic solvents is discussed.     

Model for the capture of secondary electrons by a fast ion

A capture process is discussed which is strongly assisted by the relaxation of energetic secondary electrons inside a solid target. The following processes are incorporated into the model (in a simplified form): — the production of secondary electrons by a fast projectile inside the target (in binary encounter approximation of the projectile with free target electrons), — the dynamics of the secondary electrons (in continuously slowing down approximation without elastic scattering), — the reduction of the screening of the projectile charge at the exit surface (in sudden approximation and neglecting the image charge). The capture efficiently populates Rydberg states with high angular momenta and gives high coherences between Rydberg states. The application to convoy electrons gives contributions only to the innermost part of the cusp shaped velocity spectra which is possibly caused by the neglect of elastic scattering of the secondary electrons.     

INHIBITION OF ELECTRON TRANSPORT IN CHLOROPLASTS BY CHAOTROPIC AGENTS AND THE USE OF MANGANESE AS AN ELECTRON DONOR TO PHOTOSYSTEM II*

Abstract— Incubating spinach chloroplasts with various chaotropic agents results in inhibition of photosynthetic electron transport between water and Photosystem II similar to the inhibition caused by washing chloroplasts with a high concentration of Tris buffer. Partial restoration of NADP photoreduction and fluorescence of variable yield is achieved by adding hydroquinone or Mn²⁺, either of which donates electrons to Photosystem II in the inhibited chloroplasts. The inhibitory treatments cause the release of Mn from its bound state in the chloroplast, thus allowing the measurement of the ESR signal of Mn²⁺. The ESR measurement is used to follow the photooxidation of Mn²⁺ as it donates electrons to photosystem II.     

Thermodynamics of 1,10-phenanthrolinium ion and ferrous-1,10 phenanthroline complex in dioxane—water and ethanol—water at 25°c

Enthalpies of formation of 1,10-phenanthrolinium ion and ferrous-1,10-phenanthroline (tris) complex in dioxane—water and ethanol—water media at 25°C have been determined by calorimetry. Results are discussed in the light of ion—solvent and solvent—solvent interactions.     

Thermalization lengths of “subexcitation electrons” in water determined by photoinjection from metals into electrolyte solutions

Ranges of 0–4 eV electrons in aqueous electrolyte solutions have been measured using the technique of photoinjection. Variations of the method based on investigation of the dependence of the photoinduced charges on scavenger concentration, the intensity of incident light and time (in nanosecond scale) are used. The values of electron ranges in H₂O are found to amount to 80 Å and in D₂O—110 Å. The mechanism of thermalization of slow electrons in water is discussed. It is caused, mainly, by non-local losses associated with the excitation of the vibration-rotation matter spectrum. During thermalization the slow electrons are subject to numerous elastic scatterings whose cross-section is close to a gas-phase one.     

Phase equilibrium calculations of highly polar systems

It is well known that highly polar and hydrogen bonding mixtures pose a serious challenge to equations of state. In the present report it is shown that excellent correlations and predictions of complex systems can be achieved when the van der Waals mixing rules are properly associated with an equation of state. In this report the proper form of the van der Waals mixing rules is used with the Peng—Robinson equation of state to predict the vapor—liquid equilibrium properties of water—ketone, water—alcohol, alcohol—ketone, and other complex mixtures, which exhibit either positive or negative azeotropy, with an accuracy which was not achievable by the original form of Peng—Robinson equation of state of mixtures.     

化学修饰环糊精在醇/水混合溶剂中的包结行为

环糊精 (ＣＤ)及其衍生物在主客体化学中占有重要位置［１］．在环糊精母体上引入一个荧光发色团,可使ＣＤ变为在光谱上有响应的主体化合物,如引入一个丹酰基,在水溶液中由于疏水相互作用,该荧光团易于进入ＣＤ内腔形成“自包结”配合物［２ -３］．我们曾合成了以氮氧杂 十一烷基链相连接的单个Ｎ,Ｎ二甲氨基查尔酮 (ＤＭＡＣ)修饰的 β ＣＤ衍生物 (ＤＭＡＣ ＣＤ),也表现出良好的自包结特征［４］．前人曾有吖啶／ＣＤ配合物体系与低浓度醇分子形成三元包结物的报导［５,７］,而在醇水混合溶剂中主客体配合物的稳定性研究较少．…     

Physical and Chemical Properties of Dissolved Electrons (Excess Electrons)

Electrons produced in a gaseous, liquid, or solid solvent are called dissolved electrons or excess electrons. These excess electrons can exist as quasi-free particles of high mobility in a delocalized state, comparable with electrons in a metal; or as bound particles of low mobility they can be localized within narrow limits—in a solvent cavity formed by repulsive forces. Localized electrons can also be solvated like normal ions. Characteristically, such solvated electrons exhibit broad and extensive absorption spectra in the visible to near infrared spectral range. The localized and delocalized states of the excess electrons can be in equilibrium with each other, such that a continuous transition of the properties between the limiting extremes can be observed. The reactions of the excess electrons with suitable acceptors (substrates) are initiated by an attachment-detachment equilibrium A + e^? ? A^? which is followed by further chemical rearrangements. The rate constants of these reactions vary by more than 15 powers of ten depending on the substrates and the solvents. Most of the properties of excess electrons in solution can be interpreted by means of a model which is easily understandable but quantitatively evaluated only with considerable effort.     

Interactions of open-shell systems,RHF molecular potential equations

For a supermolecule with up to two open shells the RHF equation is transformed into coupled equations for the components. This is achieved by introducing a constant number of electrons in the components as additional variation constraint. The interaction energy obtained from these equations represents polarization and exchange-polarization effects besides the first-order energy. As example MINDO/2 calculations are discussed for the systems methyl radical—ethylene, methyl radical—methyl radical, ethylene—ethylene cation.     

Effect of water—ethanol solvent on the stability of copper(<Emphasis Type="SmallCaps">ii</Emphasis>) coordination compound with the nicotinate ion

The stability constants of copper(II) complexes with nicotinate ion in water—ethanol solvent were determined by the potentiometric method at 25.0±0.1 °C and ionic strength of 0.25 (NaClO₄) in the range X_EtOH = 0—0.7 mole fractions. The stability constant of copper(II) nicotinate complex considerably increases with increasing ethanol concentration in the solvent. The contributions of reactants to the Gibbs energy of the complex formation reaction on going from water to aqueous ethanol were analyzed. The results of thermodynamic analysis of solvation effects were used to evaluate the ratio of the ion and ligand transfer Gibbs energy contributions to the change in the reaction Gibbs energy in the water—ethanol system.     

Electrochemistry of vitamin B12: Part VII. Role of the base-off/base-on reaction in the oxido-reduction in the B12r-B12s couple in non-aqueous solvents

The cyclic voltammetric study of vitamin B_12r in DMSO shows the importance of the base-on/base-off reaction in the electrochemical reduction mechanism. Depending upon the flux of electrons flowing through the system. part of the base-on complex is reduced through prior opening of the nucleotide side-chain which gives rise to the more easily reduced DMSO-Co(II) complex. The quantitative analysis of the variations of the peak heights with the sweep rate allows the thermodynamic and kinetic characterization of the base-on/base-off reactions to be determined. DMSO thus appears as a stronger ligand toward Co(II) than water, leading to an increased participation of the base-off complex in the reduction process. The greater stability of the DMSO complex is also related to the observation that electron transfer is significantly slower than in the case of the water complex. The importance of the ligand exchange reactions in the reduction of B_12r is confirmed by the effect of pyridine additions. Three complexes then participate in the reduction process, their reduction potentials lying in the order DMSO >Py >Bzm. The reduction mechanism involving the interconversion of the three complexes is described as a function of the electrode potential, the flux of electrons and the pyridine concentration. An estimation of the equilibrium and rate constants of the three ligand exchange reactions is made, based on the variations of the cyclic voltammograms with the sweep rate and the pyridine concentration.     

Ce（H2O）n3+（n=1～6）水合性质的密度泛函理论研究

以TZ2P为基组,采用Becke- Perdew(BP)等10种密度泛函分别对Ce(H2O)n3+(n=1～6)体系进行几何优化.运用绝对平均误差分析得出在所计算的10种密度泛函中Becke-PBEc为最优泛函.振动光谱分析表明,Ce(H2O)n3+(n=1～6)体系随着n增大,即H2O配位数的增加,Ce和O之间的相互作用越来越弱,O和H之间的相互作用越来越强,振动吸收频率与键长的呈现良好的线性关系.电子结构分析表明,f轨道的孤对电子不参与Ce—O之间的成键.热力学分析表明,Ce3+不易形成低配位的水合离子,但是在适当温度压强以及动力学条件下铈的低配位水合离子有可能实现转变.     

LCZ696: a dual-acting sodium supramolecular complex

LCZ696 displays several surprising features, such as an intrinsic stabilization of the supramolecular complex by monovalent multi-coordinated sodium cations and water molecules. In addition, to the best of our knowledge, the compound is the first example of a dual-acting pharmaceutical built as a supramolecular complex delivering two pharmacologic effects—angiotensin receptor 1 (AT1) blockage and neprilysin (NEP) inhibition.     

A theory of elementary photophysical processes with the participation of excess electrons in polar liquids

The main concepts of the new theory of processes with the participation of excess electrons in polar liquids are considered. The theory takes into account that (1) polar liquids are electrostatically inhomogeneous (local potentials on molecules are different) and (2) a molecule can accept an electron for a short time to produce an anion in an unstable state with a certain energy and lifetime. A discrete model of a substance consisting of molecules with constant dipole moments is used. Excess electrons in a liquid are described by energy distribution density, and the behavior of electrons, by quantum mechanics equations. The experimental data on the photoionization of water and aqueous solutions of salts and the low threshold energy of photons (～6.5 eV) at which solvated electrons appear in water are explained. The absorption spectra of water with excess electrons at the first and subsequent time moments after their photogeneration are reproduced theoretically. The dependence of the photoemission of solvated electrons from potassium-ammonia solutions on the energy of photons is interpreted. The continuous spectrum of spontaneous radiation of solvated electrons in liquid ammonia and water is calculated. The optical absorption spectra of solvated electrons in such polar liquids as water and ammonia are reproduced.     

An experimental study of three- and four-phase equilibria for isopropanol—water—carbon dioxide mixtures at elevated pressures

Compositions and molar volumes of the three phases in liquid—liquid—gas equilibrium are reported for ternary mixtures of isopropanol, water and CO₂ at elevated pressures and at temperatures of 50 and 60°C. Phase compositions and molar volumes were also obtained for three-phase, liquid—liquid—liquid equilibrium and four-phase, liquid—liquid—liquid—gas equilibrium at 40°C. Gas—liquid and liquid—liquid critical endpoints, which represent pressure bounds on the liquid—liquid—gas region at 60°C, were determined from observations of critical opalescence.The phase behavior exhibited by the isopropanol—water—CO₂ system is quite complex, particularly at conditions near the critical point of CO₂. These conditions are well within the range of operating conditions proposed for supercritical-fluid extraction of organic compounds from water using CO₂. Therefore, the existence of multiple coexisting phases can be an important factor in designing and operating such extraction processes.     

光合放氧复合物结构及其放氧机理的研究

光合水氧化是地球上最重要的生化过程之一.光合放氧生物包括光系统Ⅰ(PSⅠ)和光系统Ⅱ(PSⅡ)两种类型反应中心,光系统Ⅱ反应中心能以水作为电子给体,利用光能氧化水产生质子和氧气.对于水如何被氧化这个难题前人已做了大量的工作,但到目前为止放氧复合物(OEC)的结构及水氧化的机理仍不清楚.本文结合当前研究结果,就光合放氧复合物的结构及光合放氧机理进行了综述,希望能有助于推进这方面的工作.     

马来腈二硫纶·邻菲咯啉镍(II)配合物的电子光谱和理论研究

测量了标题配合物Ni(mnt)(phen)在多种介质中的电子吸收光谱和发射光谱, 使用密度泛函理论的B3LYP方法和分子轨道理论的PM3方法研究了其气态分子几何构型、电子结构和成键, 用ZINDO/S方法通过多组态的组态相互作用(CI)计算解释了实验光谱. 结果表明: 该配合物分子为平面结构, 对称性属于点群C_2v, 基态为自旋三重态, 配位键Ni—N和Ni—S为典型的共价结合, Ni的3d电子反馈效应较显著; 可见区的吸收带和发射带(对应于基态电子组态到较低能量激发态组态的跃迁)本质上属于配体phen到mnt^2－的荷移跃迁(LL'CT), 紫外区的吸收带本质上属于配体的π→π*跃迁.