Electronic structure,spectra, and thermodynamical functions of molybdenum pentachloride

The SCF-X -SW method in non-relativistic and quasi-relativistic versions has been used to calculate the electronic structure, ionization potentials, energies and oscillator strengths of the optical transitions in MoCl₅. The electronic absorption spectrum of the gaseous MoCl₅ has been measured. The interpretation of the photoelectron and optical spectra of MoCl₅ is given. Spinpolarization effects and relativistic corrections are discussed. The thermodynamical functions of MoCl₅ (gas) are calculated.     

An SCF XαSW study of the electronic structure and X-ray and photoelectron spectra of Fe(II) and Fe(III) hexacyano complexes in a cluster approach

The electronic structure of the hexacyano complexes [Fe(CN)₆]^4– and [Fe(CN)₆]^3– as clusters of the cyanide complex salts has been calculated by the SCF XSW method. Theoretical photoelectron, X-ray emission and absorption spectra have been constructed. The contribution of the resonance emission to the X-ray emission spectra has been estimated. On the basis of detailed comparison of the theoretical and experimental spectra an assignment of the fine structure of the spectra has been proposed.     

Electronic states of the [2 n ]cyclophanes

Low energy singlet and triplet states for a series of [2 _n ]cyclophanes are discussed in terms of the results of a simple model calculation. Experimental trends can be explained under the assumption of significant - interaction involving the saturated bridges. This interaction destabilizes low energy excimer states, in contrast to the usual red shift observed for alkylbenzenes. The observed near-constancy of the onset of the absorption spectra can be explained by near-cancelation of through-bond and through-space contributions.From 01.01.1984, Royal Danish School of Educational Studies, Department of Chemistry, DK-2400 Copenhagen NV, Denmark     

The vibrational spectra of linear and branched perchlorosilanes Si n Cl2n+2 and their simulation using a local symmetry force field

Infrared andRaman vibrational spectra ofn-Si₄Cl₁₀,n-Si₅Cl₁₂,neo-Si₅Cl₁₂ and [(SiCl₃)₃Si]₂ have been measured and assigned. A local symmetry force field has been developed to simulate vibrational spectra of all (noncyclic) perchlorosilanes Si _n Cl_2n+2 known today (n=2, 3, 4, 5, 8). The observed spectra are reproduced satisfactorily

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Die Vibrationsspektren linearer und verzweigter PerchlorsilaneSi _n Cl _2n+2 und deren Simulierung mittels eines lokalen Symmetrie-Kraftfeldes

Zusammenfassung Infrarot- undRaman-Spektren vonn-Si₄Cl₁₀,n-Si₅Cl₁₂,neo-Si₅Cl₁₂ und [(SiCl₃)₃Si]₂ wurden aufgenommen und zugeordnet. Ein lokales Symmetrie-Kraftfeld zur Simulation der Spektren aller bisher bekannten (nicht cyclischen) Perchlorsilane Si _n Cl_2n+2 (n=2, 3, 4, 5, 8) wird angegeben. Die beobachteten Spektren werden zufriedenstellend reproduziert

     

Electronic structure and electronic absorption spectra of molybdenum and tungsten oxotetrachlorides

Electronic absorption spectra of the molecules MoOCl₄ and WOCl₄ have been measured and their electronic structure has been calculated on the basis of the SCF-X-SW theory in the overlapping atomic sphere model. Ionisation potentials and allowed optical transition energies have been found in the transition state approximation. The interpretation of the electronic absorption spectra of gaseous MoOCl₄ and WOCl₄ is given.     

Synthesis and IR Spectral Study of MoO2Cl2 Molecular Complexes with Acetoacetanilides. Crystal Structure of MoO2Cl2 Complex with Acetoacet-2-Toluidine

A series of MoO₂Cl₂ complexes with acetoacetanilide derivatives were synthesized and studied by IR spectroscopy. The crystal and molecular structures of the MoO₂Cl₂ complex with acetoacet-2-toluidine (HL) were determined by X-ray diffraction analysis. The monoclinic crystals involved are a = 7.621(7) Å, b = 9.498(3) Å, c = 19.980(9) Å, = 95.16(7)°, V = 1440(2) ų, Z = 4, and space group P2₁/n. The coordination polyhedron of the Mo atom is a distorted octahedron with two O oxoatoms in the cis-position relative to each other, two Cl atoms in the trans-positions, and two O atoms (HL) in the trans-positions to O(oxo).     

The Non‐Centrosymmetric Crystal Structure of Molybdenum(VI) Oxide Bromide MoO2Br2

Red, transparent single crystals of molybdenum(VI) dioxide dibromide MoO₂Br₂ emerged as by‐product after thermal analyses of reaction mixtures comprising REBr₃ (RE = La or Gd) and MoO₃. The structure of this highly water sensitive compound can be described in the non‐centrosymmetric monoclinic space group Cc with the lattice constants a = 1522.33(15) pm, b = 390.61(4) pm, c = 771.09(8) pm, β = 104.394(7)° and four formula units per unit cell. Crystallographically unique Mo⁶⁺ cations are surrounded by four oxide and twobromide anions in the shape of distorted octahedra withthe two Br^– ligands situated in trans position to each other. These octahedra are interconnected by the four O^2– anions via vertices to form {MoO Br } layers parallel to the bc plane, whereas the bromide anions remain terminal. These sheets are piled along [100] with the Br^– anions pointing towards the center of square voids of adjacent layers.     

基于第一性原理的无铅无机钙钛矿Cs3Bi2X9(X=Cl、Br、I)光电性能表面效应研究

用基于第一性原理的密度泛函理论方法,对Cs₃Bi₂X₉（X=Cl、Br、I）的光电特性进行理论计算,并系统阐述这3种晶体的表面效应对光电性能的影响。结果表明,3种材料的光学特性由铋原子和卤素原子最外层p轨道上的价电子主导。在可见光区中,材料的吸收峰会随卤素原子序数的增加呈现红移,其中一维结构的Cs₃Bi₂Cl₉表面结构在光吸收能力上尤为特别且敏感;二维结构的Cs₃Bi₂Br₉光吸收能力会受厚度影响;零维结构的Cs₃Bi₂I₉非常稳定,且几乎不受表面特性和晶体厚度的影响。     

Electronic spectra of metal cluster molecules

The electronic absorption spectra (UV-visible-NIR) of a range of molecular metal cluster compounds, including new spectra of Pt₃₀₉(phen*)₃₆O₂₈ in solution and Au₅₅(PPh₃)₁₂Cl₆ in the solid state, are discussed and compared with the spectra of colloidal particles of the corresponding metals. We consider frontier orbital separations, the development of interband absorptions, the possible appearance of molecular plasma resonances, and charge-transfer in the solid state.     

Beiträge zur Chemie der Oxidhalogenide von Molybdän und Wolfram. I. Sättigungsdruck und Bildungsenthalpie von MoO2Br2 und MoO2CI2

Molybdenum dioxiddibromide and -dichloride have been prepared from MoO₂, Br₂, und Cl₂, respectively, and their chemical and thermochemival behaviour was studied. Their enthalpies of formation, ΔH°, have been determined from the solution enthalpies of MoO₂Br₂, and MOo₂Cl₂, in aqueous NaOH (data see ?Inhaltsübersicht”?). From their sublimation pressures, p, the enthalpies, ΔH° (subl.), and entropies, ΔS° (subl.), of sublimation have been evaluated (data see above).     

Investigation on the mechanism and applications of the reaction Cl2+2HBr=2HCl+Br2

The mechanism of reaction Cl₂+2HBr=2HCl+Br₂ has been carefully investigated with density functional theory (DFT) at B3LYP/6-311G^** level. A series of three-centred and four-centred transition states have been obtained. The activation energy (138.96 and 147.24 kJ/mol, respectively) of two bimolecular elementary reactions Cl₂+HBr→HCl+BrCl and BrCl+HBr→HCl+Br₂ is smaller than the dissociation energy of Cl₂, HBr and BrCl, indicating that it is favorable for the title reaction occurring in the bimolecular form. The reaction has been applied to the chemical engineering process of recycling Br₂ from HBr. Gaseous Cl₂ directly reacts with HBr gas, which produces gaseous mixtures containing Br₂, and liquid Br₂ and HCl are obtained by cooling the mixtures and further separated by absorption with CCl₄. The recovery percentage of Br₂ is more than 96%, and the Cl₂ remaining in liquid Br₂ is less than 3.0%. The paper provides a good example of solving the difficult problem in chemical engineering with basic theory.     

基于第一性原理的无铅无机钙钛矿Cs3Bi2X9(X=Cl、Br、I)光电性能表面效应研究

用基于第一性原理的密度泛函理论方法,对Cs₃Bi₂X₉(X=Cl、Br、I)的光电特性进行理论计算,并系统阐述这3种晶体的表面效应对光电性能的影响。结果表明,3种材料的光学特性由铋原子和卤素原子最外层p轨道上的价电子主导。在可见光区中,材料的吸收峰会随卤素原子序数的增加呈现红移,其中一维结构的Cs₃Bi₂Cl₉表面结构在光吸收能力上尤为特别且敏感;二维结构的Cs₃Bi₂Br₉光吸收能力会受厚度影响;零维结构的Cs₃Bi₂I₉非常稳定,且几乎不受表面特性和晶体厚度的影响。     

Complex compounds of tetracycline with WO 4 2− and MoO 4 2− ions. Investigation by pH-metric and conductometric methods

By using pH-metric and conductometric methods it has been found that tetracycline (H₃TC) forms with WO ₄ ^2– and MoO ₄ ^2– ions the following complex compounds: [WO₃HTC]^2–, [WO₃(H₂TC)₂]^2– and [MoO₃(H₂TC)₂]^2–. Stability constants log/gb ₁ ^k =7.86 and log ₁ ^k =7.80 for [WO₃HTC]^2– and [MoO₃HTC]^2–, respectively, have been calculated from pH-metric measurements.     

Ab initio MP2 calculations of the products of acetylene addition to HgCl2

Gas-phase reaction of acetylene with HgCl₂ resulting in -chlorovinylmercury derivatives and their interaction with Cl^– and I^– anions and KI molecule was studied by the ab initio MP2 method with the Dunning—Hay double zeta basis set and LanL pseudopotential for Hg, K, and I atoms. The reaction was shown to proceed via a -complex of acetylene and HgCl₂ (the calculated enthalpy of formation is –6.5 kcal mol^–1). According to calculations, the activation energy of formation of cis--chlorovinylmercury chloride from acetylene and HgCl₂ is 31 kcal mol^–1. Chloride and iodide anions and KI molecule are readily added to both cis- and trans-isomer of -chlorovinylmercury chloride to give stable species.     

Theoretical studies of atmospheric molecules: SCF and correlated energy levels for the NO2, NO 2 + and NO 2 − systems

SCF and MC-SCF/CI calculations were carried out on the low-lying electronic states of NO₂, NO ₂ ⁺ and NO ₂ ^– , using a double-zeta quality basis set of contracted Gaussian functions. The calculations were performed primarily at the equilibrium geometry (R _NO = 2.25 a_o, _ONO=134 °) of theX ² A ₁ state of NO₂. SCF calculations on NO ₂ ⁺ in a linear conformation were also performed. Results are presented and compared with experiment and other calculations.Research supported in part by Air Force Delivery Orders F33615-72-M-5015 and MIPR889474-00117 and Air Force Office of Scientific Research and in part by the United States Energy Research and Development Administration.     

Investigation of radical reactions in C2Cl4 and C2Cl4/O2 discharges by EPR,mass, and emission spectroscopy

The reaction of tetrachloroethylene, C₂Cl₄, with O(³P) atoms as well as the plasma decomposition of C₂Cl₄ and C₂Cl₄/O₂ mixtures have been investigated by combined application of electron paramagnetic resonance (EPR) and emission and mass spectroscopies. C₂Cl₄ plasma decomposition is shown to proceed primarily to the formation of CCl₃ radicals and chlorine-deficient products, which are ultimately involved in the formation of carbonaceous layers. A simple reaction model accounts for all the detected stable and radical species, encountered during the plasma decomposition. The model also enables order-of-magnitude estimates of decomposition rate constants to be made. The suppression of the formation of both carbonaceous layers and products C_mCl_n (m3) in C₂Cl₄/O₂ discharges is explained using results of an investigation of elementary reactions in the system C₂Cl₄/O(³P)/O₂. The stable products of C₂Cl₄/O₂ discharges, i.e., COCl₂, CCl₄, and C₂Cl₆, respectively, are shown to originate from recombination of the peroxy radicals CCl₃OO and C₂Cl₅OO.     

Structural Dynamics of Isomorphic Substitution in N,N′-Diallylbenzimidazolium Copper Halide π-Complexes [C7H5N2(C3H5)2]+[Cu2Cl3?xBrx]? (x=0, 1.60, 2.33, 3)

Two new -complexes of copper(I) halides with the 1,3-diallylbenzimidazolium cation, [C₇H₅N₂(C₃H₅)₂]⁺[Cu₂Cl_1.40Br_1.60]^– and [C₇H₅N₂(C₃H₅)₂]⁺[Cu₂Br₃]^–, have been synthesized and structurally defined (space group P2 ₁/c for both; a = 22.094(6), b = 9.272(8), c = 9.22(1) , = 118.26(4)° and a = 22.267(5), b = 9.311(3), c = 9.263(2) , = 117.51(2)°). The mutual effects of chlorine–bromine substitution and the efficiency of -interactions are discussed based on XRD data for these two compounds and for the compounds [C₇H₅N₂(C₃H₅)₂]⁺[Cu₂Cl₃]^– and [C₇H₅N₂(C₃H₅)₂]⁺[Cu₂Cl_0.67Br_2.33]^– studied previously.     

Electronic Structures, (d-p)π Conjugation Effects, and Spectroscopic Properties of Polyoxometalates: M6O19 2− (M=Cr, Mo, W)

The electronic structures and bonding of isopoly oxometalates M₆O₁₉ ^2– (M=Cr, Mo, W) have been investigated by using ab initio and relativistic density functional methods. We have discussed the role of the central oxygen atom and the (d-p) conjugation interactions between the metal and bridging oxygen atoms. It is found that there exist 12 three-centered two-electron (d-p-d) bonds for the three M₄(-O)₄ planar rings in M₆O₁₉ ^2– ions and these hexametalates are considered to have quasi-aromaticity. The (d-p) conjugation effects play essential role in stabilizing these cluster compounds, and the reduced (d-p) conjugation effects account for the instability of the isopoly oxochromate ion, Cr₆O₁₉ ^2–. The vibrational spectra and electronic spectra of M₆O₁₉ ^2– ions are evaluated and assigned theoretically and the calculated spectra are in fairly good agreement with the measured experimental results.     

The role of the π-bonding network for trigonal level splittings of tris-bidentate Cr(acac)3 and Cr(ox) 3 3−

The varying -bonding contributions in the title compounds caused by the different electronic and molecular structure of the chelate rings are used for explaining the large band splittings in the absorption spectra by trigonal symmetry. It is shown that usual ligand field theory and the angular overlap model are not able to account for the trigonal level splitting of Cr(acac)₃ for which the coordination sphere of oxygen atoms is nearly octahedrally arranged. The experimental finding can, however, be rationalized by an extended angular overlap model which considers the phase coupling of -orbitals in the ligands leading to non-additive contributions to the metal-ligand bond energy.On leave of absence from the Bulgarian Academy of Sciences, Sofia, Bulgaria