铈卤氧化物的ESCA表征（Ⅱ）—Ce的M5N45N45俄歇峰

研究了ＸＰＳ诱导的ＣｅＭ５Ｎ４５Ｎ４５俄歇峰，由于其终态空穴处于芯能级，俄歇峰有较好的分辨率，从ＣｅＭ５Ｎ４５Ｎ４５的俄歇峰可获得中心离子Ｃｅ的电子云密度等信息，发现其俄歇参数与配位体的极化变形程度有关，从而解释了双烯烃定向聚合必须有稀土卤氧键存在的原因。     

Zur theoretischen Interpretation von NMR-chemischen Verschiebungen tetrakoordinierter zentralatome. IV—CNDO/2-Berechnungen von 29Si-NMR-chemischen Verschiebungen. Der Einfluß der ΔE-Näherung

On the basis of the CNDO/2 method paramagnetic screening constants of the central atom of tetrasubstituted silicon compounds of the type Me_4–nSiX_n (X = F, OMe, NMe₂, C1) are calculated, both with and without ΔE approximation. The results are compared with the experimental ²⁹Si n.m.r. chemical shifts. The ‘averaged excitation energies’ ΔE obtained from the comparison of calculated values depend on the charge of the central atom and cannot be considered to be constant for quantitative studies.     

Extra-atomic relaxation energies for the 3d-transition metal series obtained with SCF hole-state calculations

A method to calculate extra-atomic relaxation energies is presented. It is based on the use of SCF hole-state calculations. The E_R^ea (2s) and E_R^ea (2p) values obtained for the 3d-transition metal series are in fair agreement with experimental values.     

Relaxation phenomena involved in the L3M4,5M4,5;1G4 auger process in zinc metal

A detailed analysis is presented of the L₃M_4,5M_4,5;¹G₄ Auger transition in metallic zinc. An extra-atomic relaxation term, neglected until now, is taken into account. This results in excellent agreement between calculated and experimental values of the Auger-transition energy.     

Action mechanism of antioxidation and anticorrosion and molecular design for perfluoropolyether fluid additives (I) Action mechanism of additive and property of donating-accepting electron

The combination energy and chemical adsorption energy of N-substituted perfluoropoly-alkyletherphenylamide (PFPEA) additive to perfluoropolyalkylether oxygen radical (R_fO.) and to Fe atom have been calculated by quantum chemical methods. Structural characteristics, action mechanism, property of donating-accepting electron and substituent effect for antioxidant and anticorrosive additive are investigated. It is found that HOMO of the additives is a π-molecular orbital with lone pair electron of heteroatom. The HOMO of PFPEA additive reacts with LUMO of Fe atom to result in chemical adsorption. The LUMO of additive can interact with the SOMO of R_fO. and accept electron of R_fO. to form stable addition product. The additives have the property of donating-accepting electron. The electron-releasing group, particularly, the phenyl group, introduced to N atom of phenylamide can increase the combination energy and chemical adsorption energy, and enhance the antioxidant and anticorrosive efficiency. The research achievements can provide useful information for the designing of new antioxidant and anticorrosive additive. Based on the calculated results, antioxidant and anticorrosive efficiency can be predicted roughly as the following order: compounds III>II>I>IV>V.     

Action mechanism of antioxidation and anticorrosion and molecular design for perfluoropolyether fluid additives (I)

The combination energy and chemical adsorption energy of N-substituted perfluoropoly-alkyletherphenylamide (PFPEA) additive to perfluoropolyalkylether oxygen radical (R_fO.) and to Fe atom have been calculated by quantum chemical methods. Structural characteristics, action mechanism, property of donating-accepting electron and substituent effect for antioxidant and anticorrosive additive are investigated. It is found that HOMO of the additives is a π-molecular orbital with lone pair electron of heteroatom. The HOMO of PFPEA additive reacts with LUMO of Fe atom to result in chemical adsorption. The LUMO of additive can interact with the SOMO of R_fO. and accept electron of R_fO. to form stable addition product. The additives have the property of donating-accepting electron. The electron-releasing group, particularly, the phenyl group, introduced to N atom of phenylamide can increase the combination energy and chemical adsorption energy, and enhance the antioxidant and anticorrosive efficiency. The research achievements can provide useful information for the designing of new antioxidant and anticorrosive additive. Based on the calculated results, antioxidant and anticorrosive efficiency can be predicted roughly as the following order: compounds III>II>I>IV>V.     

Study of M4,5N4,5N4,5 auger energy shifts of Cs and I in free CsI molecules

High-resolution electron beam excited M_4,5N_4,5N_4,5 Auger electron spectra of Cs and I have been measured from CsI vapour. The Auger energies of both Cs and I observed from gaseous CsI are higher than the corresponding free-atom energies due to extra-atomic relaxation. The molecular Auger results have been compared with corresponding photoelectron measurements and free-atom data. Estimates for extra-atomic relaxation energies have been extracted from the changes of the Auger parameter between molecular and atomic species and from the difference between experimental energies and energies calculated with a relativistic Dirac-Fock program, applying the point-charge model for the CsI molecule.     

Structures, IR, NMR Spectra and Thermodynamics Properties of Halogenated Compounds X-1-ZB11H10 (Z=O, S, Se;X=F, Cl, Br): A DFT Study

The halogenated compounds of twelve‐vertex closo‐1‐ZB₁₁H₁₁(Z=O, S, Se; X=F, Cl, Br) have unusual stability. The structures of halogenated isomers obtained by DFT method indicate that the halogen atoms are more likely to attack the meta vertexes. The chemical thermodynamic properties show that the halogenations are spontaneous and exothermic. The result that both the optimized and experimental cages of closo‐thiaborane have not changed after chlorination indicates that the substitution of a chlorine atom for a hydrogen atom of closo‐thiaborane happens at outer of the cage. The calculated electronic structures show that the three‐dimensioned aromaticity of cage would like positive chlorine atoms to attack. The halogenations by elemental halogen in the presence of metal halides were proved to belong to the electrophilic substitutions and the mechanism was discussed in details. The suggested transition state interpreted the experiments. The thermal rearrangement which was supposed early according to experiments was verified by the thermodynamic properties of chlorination theoretically. The IR and ¹¹B/¹H NMR isotropic chemical shifts were calculated and compared with the experimental data to reconfirm the structures of chlorinated closo‐thiaborane. Furthermore, the predictions on the halogenated closo‐oxaborane and closo‐selenaborane are significant for the syntheses.     

The effect of atomic and extra-atomic relaxation on atomic binding energies

An equivalent-cores-relaxation model is given for calculating atomic binding energies from orbital energies using only ground-state atomic properties. The agreement with experiment is excellent for the noble gases. On the basis of present knowledge of atomic relaxation, the phenomenon of “extra-atomic relaxation”, in which electronic charge is attracted toward a hole-state atom, is shown to have an important effect in lowering atomic core-level binding energies in condensed phases. This will affect the interpretation of most core-level binding energies measured to date.     

Chemical effects of satellites on X-ray emission spectra—II. A general theory of the origin of chemical effects and its application to Cl Kα spectra

A theory is presented to predict the intensity of satellites in the compounds through second order in perturbation theory. It was found that the satellite intensity is proportional to the square of the orbital-relaxation energy. We have applied the theory to the interpretation of chemical effects of K_α parasites—satellites within the natural width of main lines—of Cl compounds. The relaxation energies of the compounds have been calculated with the use of an SCC-DV-X_α MO method. The theory is in good agreement with the experimental results except for CsCl and RbCl. A reason for the exceptions is also presented.     

Action mechanism of antioxidation and anticorrosion and molecular design for perfluoropolyether fluid additives (I) --Action mechanism of additive and property of donating-accepting electron

The combination energy and chemical adsorption energy of N-substituted perfluoropoly- alkyletherphenylamide (PFPEA) additive to perfluoropolyalkylether oxygen radical (RfO.) and to Fe atom have been calculated by quantum chemical methods. Structural characteristics, action mechanism, property of donating-accepting electron and substituent effect for antioxidant and anticorrosive additive are investigated. It is found that HOMO of the additives is a p-molecular orbital with lone pair electron of heteroatom. The HOMO of PFPEA additive reacts with LUMO of Fe atom to result in chemical adsorption. The LUMO of additive can interact with the SOMO of RfO. and accept electron of RfO. to form stable addition product. The additives have the property of donating-accepting electron. The electron-releasing group, particularly, the phenyl group, introduced to N atom of phenylamide can increase the combination energy and chemical adsorption energy, and enhance the antioxidant and anticorrosive efficiency. The research achievements can provide useful information for the designing of new antioxidant and anticorrosive additive. Based on the calculated results, antioxidant and anticorrosive efficiency can be predicted roughly as the following order: compounds III＞II＞I＞IV＞V.     

Auger parameter shifts in the case of the non-local screening mechanism: Applications of the electrostatic model to molecules,solids and adsorbed species

A simple electrostatic model is applied to predict and rationalize the auger parameter shifts in molecules, solids and adsorbed species. The model is valid in the case of the non-local screening mechanism, i.e. when the screening of the core hole is due to the polarization of the nearest-neighbour ligands (no charge transfer from the ligands to localized electronic levels of the atom with the core hole, as occurs with the main peak of the core-ionized heavier 3d_n transition metal ions or the light lanthanide ions). To good approximation it is shown that: (1) the Auger parameter shift is a function of the number, distance, electronic polarizability and local symmetry of the first-neighbour ligands of the core-ionized atom; (2) the dipole–dipole interactions can play a key role in determining the extent of the extra-atomic relaxation energy and hence of the Auger parameter shift.     

Heat capacity and thermodynamic functions of 2-methylbiphenyl and 3,3′-dimethylbiphenyl in the range of 6 to 372 K

The heat capacities of 2-methylbiphenyl and 3,3′-dimethylbiphenyl are measured by means of low-temperature adiabatic calorimetry in the temperature range of 6 to 372 K. The thermodynamic characteristics of fusion and the glass transition of the investigated compounds are determined. The saturation vapor pressure and enthalpy of vaporization of 3,3′-dimethylbiphenyl are determined according to the dynamic method based on the transfer of a substance vapor in a helium flow. The absolute entropies and changes in Gibbs energies of biphenyl derivatives are calculated from the data obtained in the condensed and ideal gas states. The contribution of the C_b-(C_b) group is determined using the Benson additive method for calculating the absolute entropies of biphenyl derivatives in the liquid state (where C_b is the carbon atom in a benzene ring).     

Quadrupole coupling constants of deuterons in molecular clusters Ca<Superscript>2+</Superscript>(D<Subscript>2</Subscript>O)<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript> (<Emphasis Type="Italic">n</Emphasis> = 6, 8, 10, 18)

Characteristic features of the structure of Ca²⁺ hydration shells were considered. The results of quantum chemical calculations were compared with experimental data obtained from the study of nuclear magnetic relaxation of deuterons in aqueous solutions of calcium salts. The influence of the basis set and computational procedure on the calculated ²D quadrupole couling constants (QCC) in isolated water molecule was investigated. The ²D QCC in molecular clusters (D₂O)₅ and Ca²⁺(D₂O) _n (n =6, 8, 10, 18) were calculated using the B3LYP/6-31++G** density functional method.     

The determination of sulfoxide configuration in five-membered rings using NMR spectroscopy and DFT calculations

Cyclic five-membered ring sulfoxides and sulfones were prepared by a stepwise in situ oxidation of the corresponding sulfides with meta-chloroperbenzoic acid in an NMR tube. The oxidation was followed by NMR and both ¹H and ¹³C NMR data were collected. The geometries of all of the compounds were optimized using the DFT B3LYP/6-31G⁷ method and the ¹³C and ¹H chemical shifts were calculated for geometry-optimized structures with the DFT B3LYP/6-31++G⁷ method. The calculated ¹³C chemical shifts induced by oxidation (Δδ values) were in very good agreement with the experimental data and could be used to determine the oxidation state of the sulfur atom (–S–, –SO–, –SO₂–). The characteristic differences of the induced oxidation chemical shifts of the carbon atoms in the α-position and β-position to sulfur were successfully used to distinguish between the diastereoisomeric sulfoxides and allowed configuration determination.     

Group Additive Values for the Gas‐Phase Standard Enthalpy of Formation,Entropy and Heat Capacity of Oxygenates

A complete and consistent set of 60 Benson group additive values (GAVs) for oxygenate molecules and 97 GAVs for oxygenate radicals is provided, which allow to describe their standard enthalpies of formation, entropies and heat capacities. Approximately half of the GAVs for oxygenate molecules and the majority of the GAVs for oxygenate radicals have not been reported before. The values are derived from an extensive and accurate database of thermochemical data obtained by ab initio calculations at the CBS‐QB3 level of theory for 202 molecules and 248 radicals. These compounds include saturated and unsaturated, α‐ and β‐branched, mono‐ and bifunctional oxygenates. Internal rotations were accounted for by using one‐dimensional hindered rotor corrections. The accuracy of the database was further improved by adding bond additive corrections to the CBS‐QB3 standard enthalpies of formation. Furthermore, 14 corrections for non‐nearest‐neighbor interactions (NNI) were introduced for molecules and 12 for radicals. The validity of the constructed group additive model was established by comparing the predicted values with both ab initio calculated values and experimental data for oxygenates and oxygenate radicals. The group additive method predicts standard enthalpies of formation, entropies, and heat capacities with chemical accuracy, respectively, within 4 kJ mol^?1 and 4 J mol^?1 K^?1 for both ab initio calculated and experimental values. As an alternative, the hydrogen bond increment (HBI) method developed by Lay et al. (T. H. Lay, J. W. Bozzelli, A. M. Dean, E. R. Ritter, J. Phys. Chem.­ 1995 , 99, 14514) was used to introduce 77 new HBI structures and to calculate their thermodynamic parameters (Δ_fH°, S°, C_p°). The GAVs reported in this work can be reliably used for the prediction of thermochemical data for large oxygenate compounds, combining rapid prediction with wide‐ranging application.     

Steric effects in 31P NMR spectra: ‘Gamma’ shielding in aliphatic phosphorus compounds

An examination of published ³¹P NMR spectral data for aliphatic phosphorus compounds has revealed that chain lengthening and branching effects on the chemical shift can be interpreted in terms similar to those used for ¹³C and ¹⁵N shifts. For six families of phosphorus compounds, a β-carbon substituent was shown to deshield phosphorus, while a γ-carbon caused shielding. The effects are additive, and good agreement was obtained between ³¹P shifts calculated with the appropriate constants and the experimental values. Shielding by γ-carbon is indicative of the operation of a steric influence on ³¹P chemical shifts, not heretofore articulated. The γ-effect is also useful in explaining the unusually large shielding found in six-membered cyclic phosphines.     

Fast and Quantitative NMR Metabolite Analysis Afforded by a Paramagnetic Co‐Solute

NMR spectroscopy is an indispensable technique for the determination of the chemical identity and structure of small molecules. The method is especially recognized for its robustness and intrinsically quantitative nature, and has manifested itself as a key analytical platform for diverse fields of application, ranging from chemical synthesis to metabolomics. Unfortunately, the slow recovery of nuclear spin polarization by spin‐lattice (T₁) relaxation causes most experimental time to be lost on idle waiting. Furthermore, truly quantitative NMR (qNMR) spectroscopy requires waiting times of 5‐times the longest T₁ in the sample, making qNMR spectroscopy slow and inefficient. We demonstrate here that co‐solute paramagnetic relaxation can mitigate these two problems simultaneously. The addition of a small amount of paramagnetic gadolinium chelate, available in the form of commercial contrast‐agent solutions, enables cheap, quantitative, and efficient high‐throughput mixture analysis.     

Transferred multipolar atom model for 10β,17β‐dihydroxy‐17α‐methylestr‐4‐en‐3‐one dihydrate obtained from the biotransformation of methyloestrenolone

Biotransformation is the structural modification of compounds using enzymes as the catalysts and it plays a key role in the synthesis of pharmaceutically important compounds. 10β,17β‐Dihydroxy‐17α‐methylestr‐4‐en‐3‐one dihydrate, C₁₉H₂₈O₃·2H₂O, was obtained from the fungal biotransformation of methyloestrenolone. The structure was refined using the classical independent atom model (IAM) and a transferred multipolar atom model using the ELMAM2 database. The results from the two refinements have been compared. The ELMAM2 refinement has been found to be superior in terms of the refinement statistics. It has been shown that certain electron‐density‐derived properties can be calculated on the basis of the transferred parameters for crystals which diffract to ordinary resolution.