Photoelectron He(I) Spectra of small silanes

The photoelectron He(I) spectra of methyl-, dimethyl-, trimethyl- and ethylsiliane are reported and assigned with the help of CNDO/2 calculations.For each silane the ordering of the valence MO's obtained from calculations is, very close to that of the corresponding alkane, and is in agreement with spectral evidence. Participation of silicon d orbitals in bonding is not substantial but is more important in the outermost SiC and SiH MO's than in the π MO's mainly localized on the alkyl groups.     

Photoelectron Spectra of Azabenzenes and Azanaphthalenes: I. Pyridine,diazines, s-triazine and s-tetrazine

The experimental and theoretical basis of a recently proposed reassignment of the bands in the PE. spectra of pyridine, pyridazine, pyrimidine and pyrazine is discussed in detail. A characteristic feature of the derived orbital sequence is that it takes the ‘through-space’ and ‘through-bond’ interaction between the ‘lone pair’ basis orbitals explicitly into account. A simple parametrization of the orbital energies, based on HMO-type models for the π-orbitals and for the ‘lone pair’ linear combinations, yields excellent agreement with the observed band positions in the PE. spectra of s-triazine and s-tetrazine. Our new assignment is compared to those proposed previously.     

Photoelectron Spectra of Vicinal Tricarbonyls

The He I photoelectron spectra of tetramethylcyclopentane-1,2,3-trione 1 , 4,4,6,6-tetramethylcyclohexane-1,2,3-trione 2 , bicyclo[1.2.3]octane-2,3,4-trione 3 , bicyclo[2.2.3]nonane-2,3,4-trione 4 and anhydrous ninhydrine 5 are presented. The assignment of the first two bands is discussed using semiempirical calculations together with a qualitative band shape analysis. It is shown that the first two bands in 1 to 4 are due to the ionization of an electron from lone pair combinations of the 2p-oxygen orbitals.     

Photoelectron spectra of 1,4-benzodiazepines

Photoelectron (PE) spectra of 20 biologically active molecules of 1,4-benzodiazepine derivatives have been measured. The spectra in the range of low ionization energies (IE) were interpreted by comparison of MNDO quantum-chemical calculation data with the perturbation theory estimations. The effect of substituents and structural changes in the series studied is felt mainly by the -MOs of ring A; theortho effect is observed in the PE spectra ofortho isomers.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1583–1587, September, 1993.     

ChemInform Abstract: Photoelectron Spectra of Cyclopolysilanes

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.     

EPR Spectra of Modified Iron Oxides

Experimental data on gas-phase hydrogenation of several alkylbenzenes (toluene, ethlylbenzene, o-, m-, p-xylenes, mesitylene) over nickel catalyst are summarized. Rate dependence as a function of the chemical nature of substituent and position in the aromatic ring is discussed. The stereochemical distribution for dialkylbenzene and trialkylbenzene is addressed.     

DFT Simulation of Electron Spectra for Auger Electron and Photoelectron Spectra of Lithium Compounds

(Li, O, F)-Auger electron, and X-ray photoelectron spectra (AES, VXPS) of solid lithium compounds (Li metal, LiCl, LiF, Li₂O) are simulated by deMon density functional theory (DFT) calculations using the model molecules of the unit cell. Calculated valence XPS, core-electron binding energies (CEBE)s, and Li-, O-, and F-KVV AES for the substances correspond considerably well to experimental results. For the calculation of VXPS, the observed spectra of Li₂O pellet with chemisorbed CO₂ almost show agreement with simulation curve of the valence XPS according to the model for the 1/1 ratio of Li₂O/Li₂CO₃. In the case of AES calculation, we analyze the experimental AES with our modified Auger electron kinetic energy calculation method which corresponds to the two final-state holes at the ground state and at the transition-state in DFT calculation by removing 1 and 2 electrons, respectively. Experimental KVV AES of the Li atom, and (O, F) KVV AES of (Li₂O and LiF) in the substances almost agree well to the AES calculated with maximum kinetic energies at the ground state, and at the transition-state, respectively.     

OCS的多光子电离高分辨光电子能谱

硫氧化碳OCS是线性三原子分子，这类小分子的激发态、离子态能级结构、能级之间的相互作用及电离过程，是研究中所关心的问题．Tanaka等[1]和Kopp[2]测量了OCS的VUV吸收光谱，Frey和Schlag等[3]以同步辐射光源，用光电离共振（PIR）谱方法、Kovac[4]和Wang，Shirley等[5]以Hel为电离光源，分别采用传统的光电子能谱和高分辨光电子能谱技术研究了CO2、CS2和OCS分子从电子振动基态吸收单个光子而电离的过程．Yang和Anderson等问为了作选态的离子一分子反应利用可调谐激光rt光子吸收将OCS选择激发到某一中间态，OCS再吸收光子后…     

Photoelectron Spectroscopy (XPS) and Thermogravimetry (TG) of Pure and Supported Rhenium Oxides. 2. Rhenium Oxides on Titanium Dioxide

Ammonium perrhenate supported on titanium dioxide has been investigated in order to elucidate the interaction between the carrier and the dispersed species. The samples, containing up to 14% by weight of rhenium, have been prepared by impregnation with an ammonium perrhenate solution. The study, performed using X-ray photoelectron spectroscopy and thermogravimetric techniques, demonstrates that a different situation is present depending on the starting rhenium content and gas environment. At low rhenium content (0–2.5%), rhenium is mainly atomically dispersed as per-rhenate-like surface compound; on heating in H₂ up to 500°C, the surface compound is reduced to metal which is still in a dispersed form. In the range 2.5–10% in addition to the perrhenate-like surface compound, small crystallites of NH₄ReO₄ are initially present on the surface. During the heat treatment in hydrogen these crystallites are reduced to ReO₂. The incorporation of Re(IV) in the TiO₂ structure preserves it from further reduction. At higher rhenium content large crystallites of ammonium perrhenate are present on the titanium dioxide surface. They show the reduction behaviour expected for this compound. The data also indicate that when metallic rhenium is heated in air, the heptoxide formed reacts with the free surface of the support and is not lost by volatilization.     

The Photoelectron Spectra of NSCl,NSF and NSF3

The photoelectron spectra of NSCl and NSF₃ have been recorded. By comparison with the PE.-bands of NSF and semiempirical calculations the first bands of NSCl and NSF₃ are assigned.     

The Photoelectron Spectra of Ni,Pd, Pt-Diallyl

The He (I) photoelectron (PE.) spectra of bis (π-allyl)palladium (2a) , bis (π-allyl)platinum (3a) , bis (π-methallyl)palladium (2b) and bis (π-methallyl)-platinum (3b) have been recorded and compared with the PE. spectra of bis (π-allyl)nickel (1a) and bis (π-methallyl)nickel (1b) . By use of the He (II) PE. spectra 2a, 2b and 3b and correlations between the PE. spectra of 1–3 it is possible to assign the first seven to eight transitions in the PE. spectra of 1–3 . In contrast to previous assignments it is shown that the first band in the PE. spectrum of 1a corresponds to the ejection of an electron from 7a_u, a pure ligand orbital. The assignment proposed is supported by semiempirical calculations of the INDO-type by considering the relaxation effects explicitly using the ΔSCF and transition operator method.     

Photoelectron Spectra of Nonmetal Compounds and Their Interpretation by MO Models

The results of (low energy) photoelectron spectroscopy render possible a better appreciation of the “Nature of the Chemical Bond”. The application of this new experimental method is demonstrated utilizing representative compounds of the nonmetal elements, and a close symbiosis delineated with molecular orbital models. In particular, general consequences are discussed concerning electron deficiency, σ- and π-interactions, electron pair delocalization, and substituent effects or geometric perturbations. Photoelectron spectroscopic ionization energies permit evaluation of parameters for specified molecular groups, allow correlation with numerous other experimental data, and are didactically valuable in the teaching of general chemistry.     

PAN和PPN的HeI光电子能谱（PES）

给出了两个重要的大气污染化合物PAN和PPN的紫外光电子能谱（PES）。为了 指认PES谱,对两个分子实施了HF和OVGF方法的理论计算,并给出了它们各自的优 化几何构型、PES谱低电离能区的两个分离（PAN）为11.42 eV和12.07 eV;PPN为 11.08 eV和11.79 eV）被归于分子中主要体现“NO_2”基团贡献的最高占有分子轨 道（HOMO）和次最高占有分子轨道（SHOMO）电子电离作用结果。而PPN的第一电离 能11.08 eV低于PAN的11.42 eV,是由于PPN分子中增加的“CH_2”基团电子的给予 作用,这为PPN应具有较大的生物毒性提供合理的解释。     

Quadricyclanes. Part I: Photoelectron spectra and electronic structure

The photoelectron spectra of quadricyclane ( 3 ) and 3-methylidene quadricyclane ( 4 ) have been measured. The results served as a basis for the elucidation of the electronic structure of these compounds, which agreed with theoretical calculations. It is found that the symmetry of the HOMO of 3 is different when compared to that of its valence isomer norbornadiene ( 1 ). The results also indicate that the structure of the highest occupied orbitals cannot be derived by only considering the Walsh-orbitals of the two three-membered rings. In addition one of the Walsh-components of the four-memebered ring has to be taken into account.     

Derivatives of imidazo[5,1-c][1,4]benzoxazin-l-ones and related analogs. Part I

The bicyclic 2,3,3a,4-tetrahydro-1H-imidazo[5,1-c][1,4]benzoxazin-1-one system and the related 1,4-benzo-thiazine and 4,1]benzoxazepine analogs were synthesized. They were easily obtained by melting a suitable diamine derivative with urea. Some of them displayed very good reversible MAO-I activity selective for type A. The preparation of the intermediate amines is also given.