Theory of electron transfer in systems with intermediate link

A theory is proposed for electron transfer through an intermediate link, the theory being based on solution of the time-dependent wave equation of the system with the exact Hamiltonian by assigning a wave function in form of a linear combination of wave functions of the initial state (electron on the donor), intermediate state (electron on the intermediate link), and final state (electron on the acceptor). The squares of the moduli of the time-dependent coefficients in these wave functions represent the probabilities of finding electrons in the indicated states. The coefficients have been determined by means of Laplace transforms, and an expression has been obtained for the rate of electron transfer through the intermediate link.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 21, No. 3, pp. 288–293, May–June, 1985.     

Radiolytically generated benzene triplets as sensitizers for energy and combined electron/proton transfer processes

Pulse radiolysis technique has been employed to investigate energy and electron transfer reactions involving triplets of naphthols and hydroxybiphenyls. The transient absorption spectra obtained on pulse radiolysis of N₂-saturated solution of naphthols and hydroxybiphenyls in benzene are assigned to triplet–triplet absorption. It was found that biphenyl triplets undergo energy transfer to naphthols and hydroxybiphenyls forming the acceptor triplets. On the other hand, benzophenone triplets, favor electron transfer followed by H⁺ transfer reaction forming benzophenone ketyl radical and phenoxyl radical of the acceptor. An analogous sequence mimics with 2-naphthol triplets and using benzophenone, acetophenone or chloranil as electron acceptor.     

Excited Electron–Hole States in Molecular Chains

The eigenvalues and the eigenfunctions of molecular excitons, charge-transfer excitons, and electron–hole pairs have been found in the approximation of electron and hole transfer between the lowest unoccupied and highest occupied orbitals in a rigid molecular chain of identical photosensitive molecules, the recognized model of organic solar cells. It has been shown that as the Coulomb binding energy decreases, the wave functions become superposition of functions of the increasing number of sites and the decay time, determined by electron or hole transitions, is shorter that the transfer time of the exciton as a whole, so that energy transfer and charge transfer become interrelated processes.     

给体-受体体系分子内光致电子转移反应研究

对一类以９，１０－二甲氧基蒽为给体，双酚Ａ为连接链连接不同受体的电子给体－受体体系，通过单光子计数法测定荧光寿命，计算了体系的光致电子转移反应速率常数；通过测定氧化还原电位，计算出各电子给体－受体体系电子转移反应的自由能变化。并根据电子转移反应理论对光致电子转移速率常数与自由能变化关系进行了理论计算分析，发现本文各体系的光致电子转移速率常数的实验值与电子转移反应理论曲线吻合得比较好，同时也揭示在该     

Facilitated ion transfer of protonated primary organic amines studied by square wave voltammetry and chronoamperometry

The transfer of the protonated forms of heptylamine, octylamine, decylamine, procaine and procainamide facilitated by dibenzo-18-crown-6 from water to a solvent polymeric membrane has been investigated by using cyclic square wave voltammetry. The experimental voltammograms obtained are in good agreement with theoretical predictions. The values of the standard ion transfer potential, complexation constant and diffusion coefficient in water have been obtained from these experiments, and have been used to draw some conclusions about the lipophilicity of these species and the relative stability of the organic ammonium complexes with dibenzo-18-crown-6. The results have been compared with those provided by linear sweep voltammetry. Calibration graphs were obtained with both techniques. An interesting chronoamperometric method for the determination of the diffusion coefficient of the target ion in the membrane has been developed and applied to all these protonated amines.     

Sonovoltammetric Elucidation of Electron Transfer Rates: The Oxidation of Dimethyl‐p‐phenylenediamine in Aqueous Solution

The electrochemical oxidation of dimethyl‐p‐phenylenediamine (DMPD) in aqueous solution (pH 7 phosphate buffer) has been studied under conventional hydrodynamic and microelectrode voltammetric conditions and found to undergo a two‐electron electrochemically reversible oxidation. Upon the application of ultrasound to the system an observed shoulder emerges in the oxidation wave. This effect has been attributed to the resolution of the two‐electron transfer processes occurring: the first a relatively fast electron transfer (0.1 cm s^?1) followed by a second slower (10^?3 cm s^?1) electron transfer: under the very high mass transport rates induced by insonation an overpotential develops for the second electron transfer so leading to the observed voltammetric resolution. The range of mass transport conditions accessible via sonication allows the estimation of the two rate constants reported.     

The electrochemical behavior ofortho-nitroanilides in an aprotic medium

Electrochemical reduction ofortho-nitroanilides in an aprotic medium has been studied by polarography and ESR. It has been shown that nitroanilide anion-radicals are formed at the first reduction wave potentials. The transfer of a second electron is accompanied by subsequent reactions (autoprotonation and homogeneous electron transfer), which occur in the bulk of the solution and lead to fairly stable intermediate anion-radicals ofortho-compounds.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1067–1070, June, 1993.     

Long-range energy transfer and ionization in extended quantum systems driven by ultrashort spatially shaped laser pulses

The processes of ionization and energy transfer in a quantum system composed of two distant H atoms with an initial internuclear separation of 100 atomic units (5.29 nm) have been studied by the numerical solution of the time-dependent Schr?dinger equation beyond the Born-Oppenheimer approximation. Thereby it has been assumed that only one of the two H atoms was excited by temporally and spatially shaped laser pulses at various laser carrier frequencies. The quantum dynamics of the extended H-H system, which was taken to be initially either in an unentangled or an entangled ground state, has been explored within a linear three-dimensional model, including the two z coordinates of the electrons and the internuclear distance R. An efficient energy transfer from the laser-excited H atom (atom A) to the other H atom (atom B) and the ionization of the latter have been found. It has been shown that the physical mechanisms of the energy transfer as well as of the ionization of atom B are the Coulomb attraction of the laser driven electron of atom A by the proton of atom B and a short-range Coulomb repulsion of the two electrons when their wave functions strongly overlap in the domain of atom B.     

Theory of electron transfer in donor–acceptor pairs

The wave functions of donor–acceptor pairs before and after electron transfer are written as a product of the electron-vibrational wave functions of the donor and acceptor with allowance for the change in the number of electrons on these particles by one after transition. In this approximation, the energy of the initial state is represented as a sum of the electron-vibrational levels of the donor and acceptor and that of the final state as a sum of donor cation and acceptor anion levels. Formulas for the electron transfer probability of symmetrical and nonsymmetrical donor–acceptor pairs have been derived that express the dependence of this process on the ionization potential difference of the donor and the electron affinity of the acceptor, on the vibrational frequencies of these particles, and on temperature.     

卟啉-酞菁分子内能量传递和电子转移的溶剂效应

用稳态荧光光谱研究了以氧原子和哌嗪作为连接基的卟啉酞菁二元分子在不同溶剂中的分子内能量传递和电子转移过程结果表明;分子内的能量传递和电子转移是两个相互竞争的过程，在非极性溶剂中，激发单重态的能量传递是主要过程，而在极性溶剂中则以电子转移为主运用Rehm-Weller公式计算了两种二元化合物在不同溶剂中的电子转移反应的自由能变化△G0ET，表明溶剂的极性对电子转移反应的自由能变化△G0ET影响很大极性越大;体系中的电子转移反应的△G0ET、越负，电子转移反应越易进行由于电子转移过程较能量传递过程进行得快，所以表现为体系中能量传递效率降低而电子转移效率增大。两种二元化合物的能量传递效率（φEnT）利和电子转移效率（φET）随溶剂的极性的变化具有相同的变化趋势     

Potential-Barrier Profile for the Adiabatic Electron Transfer Reaction in the Condon Approximation

An effective reaction coordinate is introduced and a self-consistent algorithm is proposed for the calculation of the potential barrier profile of the adiabatic electron transfer reaction in a polar solvent, taking into account electron wave functions of reagents with respect to the media polarization. A change in the functions when moving along the reaction coordinate reduces significantly the activation barrier and increases the reaction rate.     

Laser-initiated copolymerization of maleic anhydride with styrene,vinyltoluene, and t-butylstyrene

Laser-initiated polymerization of charge transfer monomer complexes has been investigated using an argon ion laser. The influence of solvents, monomer feed ratio, and irradiation time on the copolymer yield and composition was evaluated. The polymer yield was found to be directly proportional to the irradiation time and the molar concentration of maleic anhydride in the monomer feed. An enhanced rate of polymerization was obtained by substituting electron donating groups in the donor monomer. Polymerization, initiation, and propagation mechanisms, via charge transfer complexes, have been discussed. Comparison of laser-induced polymerization with UV-induced polymerization suggests that laser initiation is an energy-efficient process.     

The standard redox potential of the phenyl radical/anion couple

The voltammogram of aryldiazonium tetrafluoroborates in acetonitrile (ACN), at low concentration, shows a first one-electron wave followed at a more negative potential by a small second wave; this last one corresponds to the reduction of the radical formed at the level of the first wave. Simulation of the voltammogram permits one to determine the standard redox potential of the radical/anion couple Eo(Ph./Ph-) = 0.05 V/SCE and the reduction mechanism of the diazonium cation. An electron transfer concerted with the cleavage of the C-N bond furnishes the aryl radical; this radical undergoes two competitive reactions: reduction at the electrode and H-atom transfer.     

Theoretical analysis of electron-transfer crossover reactions between complex ions. Communication 4. Reactions involving ethylenediamine complexes of cobalt and ruthenium

Conclusions Calculations have been made within the bounds of the quantum-mechanical theory of chemical reactions of the rate constants and activation enthalpies of a number of electron transfer reactions involving the ethylenediamine complexes of cobalt and ruthenium. An estimate has been obtained of the inner-sphere reorganization energy for the Co(en)₃ ^3+/2+ complexes. The transmission coefficients for electron transfer in redox systems incorporating ethylenediamine complexes of cobalt and ruthenium have been compared, which enables a conclusion to be drawn on the degree of transferred-electron delocalization in the complexes being compared.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 353–358, February, 1984.     

On evolution of non-linear waves in polytropic reacting gases

In this paper we have studied the behavior of wave motion as propagating wavelets and their culmination into shock waves in polytropic reacting gases with same \(\gamma \)-law. An expansion wave resulting from the action of receding piston has been considered and the solution to this problem has been obtained. The propagation of weak waves has been considered and the flow variables in the region bounded by the piston and the characteristic wave front have been found out. The expansive action of a receding piston undergoing an abrupt change in velocity has been discussed. Central expansion fan and shock fronts have been studied and the solutions up to first order in the physical plane have been obtained. The effects of reaction mechanism on the solutions have been analyzed in each case.     

Determination of the density and energetic distribution of electron traps in dye-sensitized nanocrystalline solar cells

Electron transport and recombination in dye-sensitized nanocrystalline solar cells (DSCs) are strongly influenced by the presence of trapping states in the titanium dioxide particles, and collection of photoinjected electrons at the contact can require times ranging from milliseconds to seconds, depending on the illumination intensity. A direct method of determining the density and energetic distribution of the trapping states responsible for slowing electron transport has been developed. It involves extraction of trapped electrons by switching the cell from an open circuit to a short circuit after a period of illumination. An advantage of this charge extraction method is that it is less sensitive than other methods to shunting of the DSC by electron transfer at the conducting glass substrate. Results derived from charge extraction measurements on DSCs (with and without compact TiO(2) blocking layers) are compared with those obtained by analysis of the open circuit photovoltage decay.     

Enhanced rate of electron transfer across gold nanoparticle-anthraquinone hybrids

An anthraquinone-Au₁₄₀ gold nanoparticle hybrid system has been synthesised and its electron transfer properties investigated. The incorporation of nanoparticles as part of a molecular linker resulted in fast electron transfer through an otherwise blocking film.     

Concerted Determination of the Hydrogen Atom and Electron Transfer Capacity of Lipid Soluble Reducing Agents

This paper describes a method based on square wave voltammetry to evaluate either the electron transfer or the hydrogen atom transfer of lipid soluble antioxidants such as dl ‐mix‐tocopherol, BHT, ethoxyquin and retynil acetate. The electron transfer (ET) capacity was evaluated by the peak current, peak potential and the area under the anodic wave, whereas the hydrogen atom transfer (HAT) capacity by the kinetic rate of the reaction between antioxidants and 2,2‐Azobis(2‐methylpropionamidine) dihydrochloride (AAPH). The results indicate that ethoxyquin and tocopherol have the highest ET and HAT capacity. However, HAT capacity of tocopherol, BHT and retinyl acetate depend on the concentration. The approach has the advantage to assess HAT and ET capacity of lipid soluble antioxidant in a single concerted protocol.     

Ion Transfer Square Wave Voltammetry of Ionic Liquid Cations with a Solvent Polymeric Membrane Ion Sensor

Square wave voltammetry (SWV) with a solvent polymeric membrane ion sensor has been applied to study the ion transfer of several ionic liquid cations, from water to a poly(vinyl chloride) membrane plasticized with 2‐nitrophenyl octyl ether. The study has mainly been focused on dialkylimidazolium and alkylpyridinium cations. The experimental voltammograms obtained are in good agreement with the theoretical predictions. The standard ion transfer potentials of the ionic liquid cations have been obtained and the values found have been used to draw some conclusions on the relationship between structure and lipophilicity. Also, a relationship between the toxicity and the ion transfer potentials of dialkylimidazolium homologues has been found.