Hydrogen Bonding between Metal‐Ion Complexes and Noncoordinated Water: Electrostatic Potentials and Interaction Energies

The hydrogen bonding of noncoordinated water molecules to each other and to water molecules that are coordinated to metal‐ion complexes has been investigated by means of a search of the Cambridge Structural Database (CSD) and through quantum chemical calculations. Tetrahedral and octahedral complexes that were both charged and neutral were studied. A general conclusion is that hydrogen bonds between noncoordinated water and coordinated water are much stronger than those between noncoordinated waters, whereas hydrogen bonds of water molecule in tetrahedral complexes are stronger than in octahedral complexes. We examined the possibility of correlating the computed interaction energies with the most positive electrostatic potentials on the interacting hydrogen atoms prior to interaction and obtained very good correlation. This study illustrates the fact that electrostatic potentials computed for ground‐state molecules, prior to interaction, can provide considerable insight into the interactions.     

The CH3N Diradical: Experimental and Theoretical Determinations of the Ionization Energies

No Abstract     

ICl3电离能的实验和理论研究

结合紫外光电子能谱实验和量子化学计算方法研究了三氯化碘的电离能．实验得到的ICl3的紫外光电子能谱是一氯化碘和氯气的混合能谱,这表明ICl3分解为ICl和Cl2．采用B3LYlP方法在6-311 G(df)基组水平上得到了ICl3分解的过渡态．计算表明ICl3分解吸收少量热量,反应的活化能为168．4kJ／mol．采用HF方法和外壳层格林函数方法(OVGF)预测了ICl3不同轨道的电离能,OVGF方法得到的ICl3第一垂直电离能为10．372eV．     

Correlation Between Polarographic Half-Wave Potentials and Electronic Spectra of Cis-Trans Complexes of Chromium (III) and Rhodium (III)

A linear correlation between half-wave potential (E^1/2) for the process M(III)→M(II) and the first d-d transition band (v) of the types cis and trans-[M(en)₂X₂]ⁿ⁺ (M=Cr(III) and Rh(III), X=ONO^?, NCS^?, F^?, Cl^?, Br^?, I^?, H₂O, DMF, DMSO, n=1, 3) was found. The plots of the difference in half-wave potential (ΔE_1/2) against the difference in the first d-d transition hand (Δv) for the cis and trans isomer are straight lines. The equations, E_1/2=β/nαF+K₁ and ΔE_1/2=(β/NαF)Δ were derived, and used to describe the linear correlations between polarographic behavior and electronic spectrum.     

Ionization Energies of 1-R-2,2-dimesitylethenols, 1,2-Dimesityl-2-phenylethenol,and Some of their Keto Tautomers

The He(Iα) PE spectra of the two pairs of 1 (Ph)- 3 and 2–4 have been recorded and assigned by comparison with spectra of related molecules, or by using simple MO arguments. This analysis shows that the PE spectra are in agreement with the assumption that the twist angles observed in the crystalline state are more or less conserved in the gas phase. The observed first adiabatic ionization energies I allow the calculation of the molar reaction enthalpy Δ_rH which accompanies the enolization of the radical cations of the title compounds. It is found that Δ_rH ≈? –?70 kJ mol^?1 is roughly the same for both keto/enol pairs, in qualitative and quantitative agreement with expectation. These results complement and correct ionization energies determined previously by mass spectrometric methods and conclusions based on them.     

Calculation of Vertical Ionization Potentials of Oxygen Difluoride,Difluoramine, and Difluoromethane by Local Density Approximation

The vertical ionization potentials of OF₂, HNF₂, and CH₂F₂ were computed by the deMon density functional program. The results are compared with earlier calculations and with experiment. The average absolute deviation of the 21 computed ionization potentials of the outer valence electrons from experiment is 0.44 eV, which compares well with 0.37 eV for frozen-orbital configuration-interaction calculations. Although this performance is not as good as perturbation corrections to Koopmans' theorem, the computation requirements are much less demanding.     

Assessing the Accuracy of SAPT(DFT) Interaction Energies by Comparison with Experimentally Derived Noble Gas Potentials and Molecular Crystal Lattice Energies

The density functional version of symmetry‐adapted perturbation theory, SAPT(DFT), is a computationally efficient method for calculating intermolecular interaction energies. We evaluate its accuracy by comparison with experimentally determined noble gas interaction potentials and sublimation enthalpies, most of which have not been previously calculated using this method. In order to compare the results with wavefunction methods, we also calculate these quantities using MP2 and, for noble gas dimers, using CCSD(T). For the crystal lattice energy calculations, we include corrections to the dispersion, electrostatic, and induction energies that account for the finite interaction distance cutoff and higher‐order induction contributions. Overall, the energy values extrapolated to the complete basis set limit show that SAPT(DFT) achieves significantly better agreement with experiment than MP2.     

ChemInform Abstract: Ab initio Study of Superalkalis. First Ionization Potentials and Thermodynamic Stability

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.     

A Quantum-Chemical and Correlation Study of Ionization of α,α'-Dihydroxyanthraquinones

The participation of states with the predominant contribution of tautomeric anthraquinoid resonance structures in ionization of 1-hydroxy- and 1,4-, 1,5-, and 1,8-dihydroxy-9,10-anthraquinones was demonstrated by quantum-chemical and correlation methods. Solvation increases the probability of formation of such structures. The bands corresponding to anthraquinoid tautomers were revealed in the experimental absorption spectra of the ionized compounds. Published data on the pH dependence of the ratio of neutral molecules, monoanions, and dianions, obtained without taking into account tautomeric structures, require revision.     

Pyrazine bridged benzyl dicobaloximes: Competition between π-interaction and steric crowding in crystal structure

Pyrazine (Pz) bridged benzyl dicobaloximes [ArCH₂Co(dioxime)₂]₂-μ-Pz [dioxime = dmgH, dpgH] have been synthesized and characterized with ¹H and ¹³C NMR. The complexes have been synthesized by a simple procedure in one-pot directly from the corresponding benzyl aqua cobaloxime. In the crystal structure of [PhCH₂Co(dpgH)₂]₂-μ-Pz, two cobaloxime units are in eclipsed form whereas they were completely staggered in the reported [EtCo(dpgH)₂]₂-μ-Pz. This is due to the π-π interaction between the axial benzyl group and phenyl ring of the equatorial dpgH group. Both cis and trans isomer crystallized together in the crystal structure of [PhCH₂Co(dpgH)(dmgH)]₂-μ-Pz. The cyclic voltammetry study in [PhCH₂Co(dioxime)₂]₂-μ-Pz [dioxime = dmgH, dpgH] shows two cobalt center mixed together due to electron delocalization through pyrazine and behaves like a monocobaloxime and the reduction potentials are much higher than the monocobaloximes.     

Study on Pair Correlation Energies of Isoelectronic Systems F~-,HF and H_2F~+

IntroductionAsawell knownfact ,thecalculationofelectroncor relationenergyisabottleneckprobleminthecalculationsofmolecularpropertiesandchemicalreactionsinquantumchemistry .1Ithasattractedgreatattentionoftheoreticalchemists.NumerousdifferentmethodshavebeenusedtocalculatethecorrelationenergysinceL wdin2 givethedef initionofelectroncorrelationin 195 9.In 196 0s ,Sinanoˇglu3,4 definedtheexactelectronpaircorrelationen ergyanddevelopedmany electrontheoryofatomsandmoleculesinwhichthetotalcorrelation…     

Nitric oxide release: part III. Measurement and reporting

Nitric oxide's expansive physiological and regulatory roles have driven the development of therapies for human disease that would benefit from exogenous NO administration. Already a number of therapies utilizing gaseous NO or NO donors capable of storing and delivering NO have been proposed and designed to exploit NO's influence on the cardiovascular system, cancer biology, the immune response, and wound healing. As described in Nitric oxide release: Part I. Macromolecular scaffolds and Part II. Therapeutic applications, the preparation of new NO-release strategies/formulations and the study of their therapeutic utility are increasing rapidly. However, comparison of such studies remains difficult due to the diversity of scaffolds, NO measurement strategies, and reporting methods employed across disciplines. This tutorial review highlights useful analytical techniques for the detection and measurement of NO. We also stress the importance of reporting NO delivery characteristics to allow appropriate comparison of NO between studies as a function of material and intended application.     

乙胺和二甲胺分子(n_N,3s)里德堡态共振的多光子电离

MPI质谱研究作为化学分析和研究光物理过程的工具受到广泛的重视[1－4]．REMPI的特征过程是，首先分子吸收。个光子共振激发到中间态，然后处于中间激发态的分子再吸收n个光子激发到电离连续区[5]．REMPI的谱特征可以给出中间态分布的详细信息[6]，利用REMPI过程可研究单光子跃     

NH_(2-3)~(0-1 )离解能等的高级ab initio计算与评价

FeiQi等人[1]最近对H2N－H、H2N －H的离解能以及NH3、NH2的电离能，用真空紫外光电离实验进行了重新测定，并同时得到了H2N－H 的离解能．他们还在QCISD（T）／6－311＋G（3df，ZP）／／MPZ（full）／6刁IG（d）水平（GZ理论的参考水平）上对这些数据及其它相关分子的某些性质     

Application of The Xα and PM3 Methods to Chloromethanes: Ionization Potentials and Electron Affinities

The resonance energies for attachment of an electron to the chloromethanes and the ionization potentials of the chloromethanes were studied both by the multiple scattering Xα-SCF method and by the PM3 method. An external positively charged Watson sphere is used to stabilize the resonances in the Xα method. The calculated results provide support for the assignment of the features observed in the electron transmission spectra of the chloromethanes.