Are antiaromatic rings stacked face-to-face aromatic?

The stacking of 4n pi electron hydrocarbon rings into superphane structures can eliminate their antiaromaticity and result in through-space three-dimensional aromatic character. This is demonstrated by the bond length equalized geometries and diatropic NICS values of the methano-bridged superphane series with interacting three- to nine-membered 4n pi electron rings. Along with triplet and M?bius strategies, stacking is the third way to achieve aromatic ring systems with 4n pi electrons.     

Multipole expansions for numerical orbital products

The product of two numerically defined atomic angular momentum orbitals at different centers is considered. The product can be expanded about a third center on the line segment joining the two centers. A numerical procedure for evaluating the expansion functions is developed. The application of the expansion to the evaluation of four‐center electron–electron repulsion integrals is discussed. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2007     

A comment on a theory of electron affinities

Simons and Smith have calculated electron affinities and ionization potentials through third order in the electronic interaction by invoking the equations of motion method. An alternative analysis of the order is offered here by expanding the denominator in their pseudoeigenvalue equation to generate a Rayleigh-Schrödinger-like perturbation expansion. It is shown that considering the off-diagonal terms in the self-energy denominator leads to terms not considered by Simons and Smith which are third order in the electronic interaction as counted in our expansion. The connection with the diagram methods of Cederbaum is made.     

The dynamics of Rydberg electron wavepackets in NO

Rydberg electron wavepackets have been studied in molecular NO for a variety of rotational states of the ion core. Predominantly radial motion of the electron wavepacket is observed which is similar to that previously reported in atomic systems. Interference effects similar to those observed in unperturbed Rydberg series are evident and third and fourth order partial revivals are identified. Most interestingly, when the classical period of electronic motion is close to the classical period of rotation of the molecular ion, the molecular dynamics dominates the electronic dynamics.     

Effect of third metal on the electrocatalytic activity of PtRu/Vulcan for methanol electro-oxidation

The effect of a third metal on the activity of PtRu/Vulcan toward methanol oxidation reaction (MOR) is studied. An efficient method to prepare ternary catalysts was used, which allows the introduction of the third metal to PtRu/Vulcan without altering its particle size or dispersion. Ni, Mo, Co, and Ir were chosen and added to PtRu/Vulcan, based on theoretical and experimental literature results, anticipating enhancement in the catalytic activity of PtRu/Vulcan. The composition of the third metal can be varied from trace to considerable amounts. Transmission electron microscopy and energy-dispersive X-ray analysis were used to determine the particle size, dispersion, and the composition of the ternary catalysts. Cylic voltammetry, chronoamperometry, and CO-stripping voltammetry were used to analyze and compare the activities of the catalysts at 25 °C. It has been found that the addition of even trace amounts of third metal significantly affects the catalytic activity of PtRu toward MOR.     

A Pyrene-Fused Dimerized Acceptor for Ternary Organic Solar Cells with 19% Efficiency and High Thermal Stability

A pyrene-fused dimerized electron acceptor has been successfully synthesized and subsequently incorporated as the third component in ternary organic solar cells (OSCs). Diverging from the traditional dimerized acceptors with a linear configuration, this novel electron acceptor displays a distinctive “butterfly-like” structure, comprising two Y-acceptors as wings fused with a pyrene-based backbone. The extended π-conjugated backbone and the electron-donating nature of pyrene enable the new acceptor to show low solubility, elevated glass transition temperature (T_g), and low-lying frontier energy levels. Consequently, the new dimerized acceptor seamlessly integrates as the third component into ternary OSCs, enhancing electron transporting properties, reducing non-radiative voltage loss, and elevating open-circuit voltage. These merits have enabled the ternary OSCs to show an exceptional efficiency of 19.07%, a marked improvement compared to the 17.6% attained in binary OSCs. More importantly, the high T_g exhibited by the pyrene-fused electron acceptor helps to stabilize the morphology of the photoactive layer thermal-treated at 70 °C, retaining 88.7% efficiency over 600 hours. For comparison, binary OSCs experience a decline to 73.7% efficiency after the same duration. These results indicate that the “butterfly-like” design and the incorporation of a pyrene unit is a promising strategy in the development of dimerized electron acceptors for OSCs.     

Coulomb liquids along Phase Boundaries

Three areas in which Coulomb interactions are of obvious importance are considered in turn, namely liquid alkali metals, electron–hole droplets, and lithium halides. The focus in the first two areas is dominantly on critical point properties, whereas in the third area the solid–liquid transition is the predominant interest.     

电聚高分子膜固定化酶生物传感器及其进展

本文将电化学聚合高分子膜固定膜酶制备的生物传感器分为以下三种主要类型，并分别 就其发展概况和发展方向进行了评述。即：以溶解氧为电子受体的的生物传感器（第一代电流型生物传感器）；以非氧介全为电子受体的生物传感器（第二代电流型生物传感器）和电子在酶和聚合高分膜之间直接进行转移的传感器（第三代电流型生物传感器）。     

Application of many-body rayleigh-schrödinger perturbation theory to calculation of ionization potentials and electron affinities

The ionization potentials and electron affinities are calculated by the use of the many-body Rayleigh-Schrödinger perturbation theory. This approach is elaborated up to the third order, where each perturbation contribution can be interpreted by the diagrammatic method. Some simple illustrative calculations of π-electron systems are carried out.     

Photo-oxidation of diglycine in confined media Relaxation of longitudinal magnetization in spin correlated radical pairs

Time-resolved electron paramagnetic resonance spectra (X-band) of correlated radical pairs created in AOT reverse micelles are presented and simulated using the microreactor model. They are discussed in terms of the two-site model with a particular emphasis on longitudinal relaxation mechanisms. The geminate radical pair is created by photo-oxidation of dyglicine by the excited triplet states of an anthraquinone salt. The strong chemically induced electron spin polarization observed is due to three mechanisms: TM, RPM, and SCRPM. Relative contributions from these mechanisms depend on the water pool volume and the time of observation. There are three types of longitudinal relaxation in radical pairs. The first is relaxation of the RPM induced longitudinal magnetization in spin correlated radical pairs. The second is the longitudinal relaxation in radical pairs which are not correlated (with a zero value of the double quantum coherence). In such pairs, the generation of longitudinal magnetization due to RPM is impossible, and the spin-selective recombination of the pairs is ineffective. Under all experimental conditions, the first type of relaxation is slower than the second type. For both, the physical mechanism leading to relaxation is modulation of the Heisenberg electron spin exchange interaction. This is an internal relaxation process. The third relaxation type occurs in radical pairs due to ordinary longitudinal relaxation in non-interacting radicals. Normally, relaxation of the third type is the slowest of the three. This explains time and micelle size dependence of the relative contribution of RPM into TREPR spectra. It seems reasonable to suggest that the creation of the initial spin state populations is partially adiabatic.     

Soliton model of electron transfer in mixed-valence dimers and trimers

The soliton approximation is examined for mixed-valence dimers and trimers with one migrating electron. The calculations use Hamilton's canonical equations and a time-dependent wave function of the soliton type. In the two limiting cases (strong and weak vibronic coupling), the soliton approximation correlates well with the exact analytical solution. As in the adiabatic approximation at g²/v=1, the delocalized limit (quasifree electron) is transformed to the localized one (electron locked on the center). For molecular trimers, the soliton approximation allows us to reveal the cases where the transfer of an electron from the first to the third center is accompanied by electron density concentration on the intermediate center. Institute of Chemistry, Academy of Sciences, Moldova Republic. Translated fromZhurnal Strukturnoi Khimii, Vol. 35, No. 6, pp. 46–53, November–December, 1994. Translated by L. Smolina     

Some unexpected relationships between first,second and third derivative electron repulsion integrals for diatomic and triatomic molecules

It is demonstrated that for diatomic molecules, second and third derivative electron repulsion integrals need not be explicitly evaluated. Similarly for triatomic molecules an analogous simplification applies to all second derivative and 94% of all third derivative integrals. Such higher integral derivatives may be determined from intermediate quantities required in the evaluation of integral first derivatives, in conjunction with translational and rotational invariance properties. This result also has implications for theoretical studies of tetra-atomic and larger molecules. Specifically, the evaluation of most two- and three-center integral derivatives becomes very efficient.     

Mg-Y合金的电子理论研究

添加稀土元素Y,可以显著提高镁合金的力学性能特别是高温力学性能。通过固体与分子经验电子理论(EET)对Mg-Y合金进行了价电子结构分析：纯金属晶体计算结果显示Y应处于第五杂阶,证实了Mg应处于第三杂阶。对比Mg-Al合金,阐明了Y优于Al在镁合金中的固溶强化作用的电子理论依据是键能得到增强;同时用电子理论解释了Mg24Y5中间相在镁合金中具有显著强化作用的原因是Y原子占据八面体中心位置,Mg—Y键有效强化了合金基体。     

环氧氯丙烷与环氧乙烷及环氧丙烷的三元共聚

研究了用三异丁基铝-磷酸-含氮含硫给电子化合物作为催化剂使环氧氯丙烷、环氧乙烷及环氧丙烷三元共聚的行为。结果指出,作为催化剂第三组分以二甲基苯胺的效果最好。催化体系中存在与磷酸相等克分子的水时催化活性较高。酸铝比在0.25及胺铝比在0.2时活性最高。三异丁基铝用量占总单体重量的2.5％,70℃,4小时聚合转化率可达95％左右,共聚物的η_i达到2附近。通过共聚物氯含量的测定及利用核磁共振波谱仪测定环氧丙烷链节含量,求得共聚过程中各单体组分的变化。固定单体中环氧氯丙烷配比,改变环氧丙烷及环氧乙烷配比,则随环氧丙烷比例增加,所得共聚物η_i下降,T_g呈现最小值的变化。     

Ar的第三谱带240nm中心谱区与气压关系的实验观察

采用强流相对论电子束横向泵浦纯氩,获得了属于Ar的第三谱带范围内240nm中心谱区的光强随气压变化的关系.结果表明,压强为3×10⁵Pa时是产生这一谱区的最佳气压,并证实了这一谱区是由带电的原子团簇产生的.     

Analysis of the equation-of-motion theory of electron affinities and ionization potentials

An analysis of the equation-of-motion (EOM) method for computing molecular electron affinities and ionization potentials is presented. The method is compared with the Dyson equation approach of Green function theory. Particular emphasis is devoted to clarifying the similarities between these two theories when carried out to second and to third order. The Epstein—Nesbet hamiltonian and the notion of diagonal scattering renormalization have been used to systematize this comparison.     

New relativistic ANO basis sets for transition metal atoms

New basis sets of the atomic natural orbital (ANO) type have been developed for the first, second, and third row transition metal atoms. The ANOs have been obtained from the average density matrix of the ground and lowest excited states of the atom, the positive and negative ions, and the atom in an electric field. Scalar relativistic effects are included through the use of a Douglas-Kroll-Hess Hamiltonian. Multiconfigurational wave functions have been used with dynamic correlation included using second order perturbation theory (CASSCF/CASPT2). The basis sets are applied in calculations of ionization energies, electron affinities, and excitation energies for all atoms and polarizabilities for spherically symmetric atoms. These calculations include spin-orbit coupling using a variation-perturbation approach. Computed ionization energies have an accuracy better than 0.2 eV in most cases. The accuracy of computed electron affinities is the same except in cases where the experimental values are smaller than 0.5 eV. Accurate results are obtained for the polarizabilities of atoms with spherical symmetry. Multiplet levels are presented for some of the third row transition metals.     

Many-body calculation of the electric field gradient in the hydrogen molecule

The electric field gradient in the hydrogen molecule has been calculated by diagrammatic many-body perturbation theory (MBPT ) in Gaussian basis sets. The procedure through third order in electron correlation gives a value for the field gradient of 0.34041 a.u., which is 0.8% greater than the accurate value. The result is discussed in terms of the completeness of the basis sets and the convergence of the perturbation expansion.     

Effect of dimensionality of a crystal lattice on the properties of a localized impurity

The changes of electron density due to the presence of a localized impurity in a crystal lattice are examined in dependence on the lattice dimensionality. The Koster–Slater impurity model developed for the case of a three-dimensional simple cubic lattice has been taken as the basis of examinations. Ordinary bound states, virtual bound states, and delocalized electron states are considered in each lattice case. For the delocalized states extended in a one-dimensional lattice the amplitude of the oscillatory changes of the electron density due to the impurity perturbation does not decrease with the distance from the impurity position, whereas for a two-dimensional lattice this amplitude decreases roughly proportionally to the reciprocal value of the square root of the distance from the impurity. Let us note that a well-known amplitude characterizing the decrease of the oscillatory change of the electron density in a three-dimensional system is proportional to the reciprocal value of the third power of the distance from the impurity position. © 2000 John Wiley & Sons, Inc. Int J Quant Chem 79: 57–74, 2000     

Electron Transfer Spectra of the Hexachloro- and Hexabromoniobate(V) and Tantalate(V) Anions

The electron transfer spectra of the hexachloro- and hexabromoniobate (V), and-tantalate(V) anions are investigated with particular care to avoid hydrolysis products. New interpretations are given, and the optical electronegativities χ of Nb(V) and Ta(V) are recalculated. The difference between both χ values is 0.2, in better agreement with the differences observed for metals of the second and third transition series.