Valence band photoelectron spectra of transition-metal cyanides

X-ray photoelectron spectra of the valence bands of NaCN, Li₄Fe(CN)₆, Li₃Fe(CN)₆, Ni(CN)₂, Li₂Pt(CN)₄ and LiSCN have been measured and interpreted. Normalization of the valence-band intensities by equalization of the nitrogen is intensities made it possible to distinguish between cyanide and transition-metal bands. The spectrum of CN⁻ is similar to that of the iso-electronic molecules N₂ and CO. The transition-metal bands occur at a lower binding energy than the CN⁻ bands and do not show structure. From the intensities we conclude that much less mixing of the metal and ligand orbitals takes place than indicated by recent MO calculations.     

Spin–orbit effects on magnetically induced current densities in the () clusters

This study reports the spin–orbit effects on the aromaticity of the , , , , , and anionic clusters via the magnetically induced current‐density method. All‐electron density functional theory (DFT) calculations were carried out using the four‐component Dirac‐Coulomb (DC) hamiltonian, including scalar and spin–orbit relativistic effects. The magnetic index of aromaticity was calculated by numerical integration over the current flow between two atoms in the pentagonal ring. These values were compared to the spin‐free values (spin–orbit coupling switched off), in order to assess the spin–orbit effect on aromaticity. It was found that in the heavy anions, and , there is a significant influence of the spin–orbit coupling. © 2018 Wiley Periodicals, Inc.     

Theoretical investigation of photoelectron spectra of furan,pyrrole, thiophene,and selenole

The ionization spectra of furan, pyrrole, thiophene, and selenophene have been calculated within the framework of the nonempirical quantum-chemical method with the Green's one-particle function in the approximation of the third order algebraic diagram construction [ADC(3)]. The calculated energies and the intensity of vertical transitions pertaining to the ionization of outer and inner shells are compared with the newest experimental data. The good agreement of theoretical and experimental results enabled a detailed assignment and interpretation of the observed photoelectron spectra to be carried out. Problems of disturbing the picture of orbital ionization are considered; the mechanism of formation of low-lying photoelectron satellites is explained. Certain general rules and trends of the behavior of the spectra of the systems studied are considered. Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70^th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1366–1379. September, 2008.     

Different mutual positions of double bonds in open carbon chains and corresponding information from magnetically induced current densities

Magnetically induced current densities have been extensively utilized to investigate aromaticity. However, an applied external magnetic field induces a current in all chemical bonds. The present work investigates the values and patterns of magnetically induced current densities in open hydrocarbon chains containing two or more CC double bonds, considering the three possibilities for the mutual positions of the double bonds (conjugated, isolated, and consecutive) and comparing the corresponding current patterns. The patterns for chains containing three conjugated double bonds are also compared with the patterns in the aromatic benzene ring. The study highlights different current patterns for the three categories of double-bonds arrangements. The differences can be interpreted in terms of presence or absence of electron delocalization (present only in the case of conjugated double bonds) and, for consecutive double bonds, also in terms of the mutual perpendicularity of the π orbitals of adjacent double bonds.     

Molecular-orbital calculations on transition-metal complexes: Charge-transfer transitions and the interpretation of photoelectron spectra

The results of some molecular-orbital calculations on some transition-metal complexes according to a novel all-valence electron method are summarized. A comparison is made between the calculated and experimental charge-transfer spectra. In addition, attention is drawn to the remarkable sequence of the energy levels and the resulting consequences for the interpretation of photoelectron spectra.     

An investigation of aromaticity in hydroxybenzenes based on the study of magnetically induced current density

Hydroxybenzenes are derivatives of benzene in which one or more H atoms are replaced by OH groups. This work considers the effect of such replacement on the aromaticity of the ring, by assessing the aromaticity through the values and patterns of the magnetically induced current density. The results show that aromaticity is quenched and the quenching depends on the number and positions of the substituting OH groups. The isosurfaces of the magnitude of the current density also highlight connections between the donor and acceptor atoms forming an intramolecular hydrogen bond.     

Theoretical investigation of carotenoid ultraviolet spectra

We have determined the π band‐gaps of the main carotenoids present in poly(methyl)methacrylate/buriti blends, namely, trans‐β‐carotene, 13‐cis‐β‐carotene, 9‐cis‐β‐carotene, phytofluene, and zeaxanthin. Semiempirical, model Hamiltonian, and density functional calculations were carried out to study these structures. The geometries were fully optimized using AM1, PM3, and B3LYP/6‐31G(d,p) methods. The TD‐DFT and ZINDO/S methods were applied for the calculation of the electronic absorption spectra of the optimized B3LYP geometries. The calculated spectra using the polarizable continuum model for the solvent effects were compared with the available experimental. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009     

Theoretical and experimental X-ray photoelectron spectroscopy investigation of ion-implanted nafion

The membrane properties of a Nafion surface can be modified by ion implantation with N⁺ or F⁺. The results are presented of an X-ray photoelectron spectroscopy (XPS) study of implanted surfaces. For the interpretation of the XPS spectra, calculations using a semiempirical quantum chemical formalism (AM1) have been applied, in conjunction with a charge-potential model, to predict the C_1s core electron binding energies. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 551–556, 2004     

Dynamic effect on the structure of X-ray photoelectron spectra of lanthanide fluorides and oxides

Dynamic effect on the fine structure of X-ray photoelectron spectra of lanthanide oxides and fluorides is discussed. The Ln4p electron spectra are considerably complicated by the interaction between the configurations of themain one-hole and additional two-hole final states of 4p⁵4d⁵⁴fⁿ ↔ 4p⁶4d⁸fⁿ⁺¹ type. The effect of the nature of atoms in the nearest environment of lanthanide ions on the fine structure parameters is evaluated. Translated fromZhurnal Struktumoi Khimii, Vol. 39, No. 6, pp. 1059–1066, November–December, 1998.     

Theoretical study of many-body effects in the photoelectron spectra of unsaturated hydrocarbons

A theoretical investigation on the core and valence photoelectron spectra of unsaturated hydrocarbons of increasing complexity, ethylene, trans-butadiene, and trans-hexatriene, has been performed in order to analyze the role of the most important many-body effects on the spectral features and the evolution of these effects along the series. The capability of various configuration interaction (CI ) schemes to interpret both the core and the valence ionization satellite structures has been pointed out. The 3h-2v(π)-1p and 2h–1p CI schemes employed, together with an accurate choice of the basis set and the explicit inclusion of the relaxation, has proven to be very useful tools for this kind of study, being sufficiently accurate to explain the most important correlation features and extendible, at the same time, to longer chain systems. © 1994 John Wiley & Sons, Inc.     

Theoretical reconstruction and elementwise analysis of photoelectron spectra for imidazolium-based ionic liquids

We have recently measured core level and valence band XPS, UPS, and MIES spectra of two room temperature ionic liquids composed of bis(trifluoromethylsulfonyl)imide anions ([Tf(2)N](-)) and either 1-ethyl-3-methyl-imidazolium ([EMIm](+)) or 1-octyl-3-methyl-imidazolium cations ([OMIm](+)). [T. Ikari, A. Keppler, M. Reinm?ller, W. J. D. Beenken, S. Krischok, M. Marschewski, W. Maus-Friedrichs, O. H?fft and F. Endres, e-J. Surf. Sci. Nanotechnol., 2010, 8, 241.] In the present work we analyze these spectra by means of partial density of states (pDOS) as calculated from a single ion pair of the respective ionic liquid using density functional theory (DFT). Subsequently we reconstruct the XPS and UPS spectra by considering photoemission cross sections and analyze the MIES spectra by pDOS, which provides us decisive hints to the ionic liquid surface structure.     

Theoretical study of shake-up in the core photoelectron spectra of the alkali atoms

Relativistic and non-relativistic Hartree-Fock calculations have been performed for the shake-up lines relative to core ionization of the alkali atoms. Good general agreement with the experimental data is achieved both for the energy and the intensity. Relativistic effects are found to be small, amounting TO = 0.2 eV in Cs. As concerns the shake-up energies, a correlation effect is detected, the magnitude of which increases along the series.     

Theoretical investigation of one- and two-photon spectra of pyrazabole chromophores

Abstract  

An extensive series of pyrazabole chromophores containing pseudo-conjugated systems have been theoretically constructed and investigated on the one-photon absorption (OPA) and two-photon absorption (TPA) properties by using density functional theory and Zerner’s intermediate neglect of differential overlap methods. The results indicated that all the pyrazabole chromophores show strong OPA at around 400 nm and intense TPA properties in the range of 500–600 nm with TPA cross sections (δ _max) as large as 540–3,560 GM, which are excellent candidates for optical power limiting materials. It is noteworthy that the δ _max values of the two constructed pyrazaboles, PA3 and PAF2, are 308.8 GM at 772.0 nm and 157.8 GM at 834.4 nm, respectively, which may be particularly attractive as probes for two-photon fluorescence imaging. The influence of incorporating electron acceptors in the central core, π-conjugated bridge and terminal groups on OPA and TPA properties was analyzed in detail to derive structure–property relationships and to lay the guidelines for both spectral tuning and amplification of molecular TPA in the target region. Meanwhile, the solvent effects on these properties were taken into account within the PCM model. The solvent has a significant impact on the TPA properties for chromophore PA3 and leads to the two-photon absorption spectra (λ _max ^T ) red-shift and δ _max enhancing relative to those in gas phase. In addition, from the calculations of molecule AlA2, we can draw the conclusion that the compounds with the Al₂N₄ center behave similarly to pyrazabole chromophores in the linear optical and TPA properties and increase TPA cross sections to some extent.     

Theoretical investigation of the coordination of dibenzazepine to transition-metal complexes: A DFT study

DFT calculations with full geometry optimizations have been carried out on a series of hypothetical compounds of the CpM(C₁₄NH₁₁) and (CO)₃M(C₁₄NH₁₁) (M = transition metal and C₁₄NH₁₁ = dibenzazepine ligand) type. A rationalization of the bonding in hypothetical complexes is provided. Depending on the electron count and the nature of the metal, the dibenzazepine ligand can bind to the metal through the η¹, η², η³, η⁴ , η⁵, η⁶ , or η⁷ coordination mode adopting structures of types a or b. In the investigated species, the most favored closed-shell count is 18-MVE except for the Sc and V models which prefer the 16-MVE configuration.     

Theoretical investigation on the structures,densities, and detonation properties of polynitrotetraazaoctahydroanthracenes

The polynitrotetraazaoctahydroanthracenes were optimized to obtain their molecular geometries and electronic structures at density functional theory–B3LYP/6‐31+G(d) level. Detonation velocities (D) and detonation pressures (P) were estimated for this nitramine compounds using Kamlet‐Jacobs equations, based on the theoretical densities (ρ) and heats of formation. It is found that there are good linear relationships between volume, density, detonation velocity, detonation pressure and the number of nitro group. Thermal stability of the compounds was investigated by calculating the bond dissociation energies and energy gap (ΔE_LUMO–HOMO). The simulation results reveal that molecule H performs similarly to famous explosive RDX. These results provide basic information for molecular design of novel high energetic density compounds. © 2011 Wiley Periodicals, Inc.     

Theoretical investigation of the structure and vibrational spectra of carbamoyl azide

Molecular structure and vibrational frequencies of carbamoyl azide NH2CO-NNN have been investigated with ab initio and density functional theory (DFT) methods. The molecular geometries for all the possible conformers of the molecule were optimized using DFT-B3LYP, DFT-BLYP and MP2 applying the standard 6-311++G** basis set. From the calculations, the molecule was predicted to exist predominantly in cis conformation with the cis-trans rotational barrier of about 7.91-9.10 kcal/mol depending on the level of theory applied. The vibrational frequencies and the corresponding vibrational assignments of carbamoyl azide in Cs symmetry were examined theoretically and the calculated Infrared and Raman spectra of the molecule in the cis conformation were plotted. Observed frequencies for normal modes were compare with those calculated from normal mode coordinate analysis carried out on the basis of ab initio and DFT force fields using the standard 6-311++G** basis set of the theoretical optimized geometry. Theoretical IR intensities and Raman activities are reported.     

阿魏酸分子结构和振动光谱的理论研究

阿魏酸是一种有效的天然油脂抗氧化剂.采用密度泛函理论(DFT) B3LYP方法和从头算HF两种方法,在6-311++G**基组水平上对阿魏酸分子的几何结构进行全优化,得到其几何结构参数,进一步计算得到阿魏酸的红外和拉曼振动光谱.计算结果表明,采用B3LYP和HF 2种方法优化得到的几何结构及频率值是一致的,对在B3LYP方法下计算得到的红外和拉曼振动频率进行合理的理论归属并与SDBS数据库实验数据进行比较,发现计算得到的红外和拉曼振动频率与实验测定结果符合较好.阿魏酸分子结构和振动光谱的研究,为研究阿魏酸及其衍生物的化学结构与生理活性之间的构效关系提供依据.     

Theory of lineshape in photoelectron and Auger spectra

A theory of lineshape in photoelectron spectra is developed based on the Green’s function calculation of the atomic vacancy structure. It is shown that the broadening of photoelectron lines is always somewhat asymmetrical, and the broadening of satellite lines arising in atomic photoionization is generally strongly asymmetrical and inverse. The approach is generalized to low-energy Auger spectra; it is shown that Auger decay lines of excited atomic states may narrow with respect to the width of the initial level. The results are compared with experimental photoelectron spectra. Translated fromZhurnal Strukturnoi Khimii, Vol. 39, No. 6, pp. 985–991, November–December, 1998.