X-ray emission and X-ray photoelectron study of the electronic structure of polymeric cubanocluster compounds Re4−x Mo x S4Te4

The electronic structure of cubanocluster compounds of the series Re_4−xMo_xS₄Te₄ was studied by X-ray emission and X-ray photoelectron spectroscopy. The electronic structure of the (Re₄S₄)⁸⁺ cluster was calculated by the EHT method. It is shown that replacement of rhenium atoms by molybdenum atoms leads to changes both in the chemical bonds of the Re₄S₄ cubanocluster fragment and in the bond of the latter with the Te₄ fragment. Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 37, No. 5, pp. 901–906, September–October, 1996. Translated by L. Smolina     

Coordination chemistry of copper(II) complexes with N4, N4S2, and N4O2 donor macrocyclic ligands: Biological aspects—antifungal, synthesis, spectral studies, and magnetic moments

Three macrocyclic ligands and their complexes with copper(II) salts (with anions Cl⁻, NO ₃ ⁻ , and NCS⁻) were prepared and investigated using a combination of microanalytical analysis, melting point, molar conductance measurement, magnetic susceptibility measurement, and electronic, IR and ESR spectral studies. Ligands L¹, L², and L³ having N₄, N₄O₂, and N₄S₂ core, respectively, and all the donor atoms of these ligands are bonded with Cu, which is confirmed by a seven-line pattern observed at half-field in the frozen (H₂O: MeOH = 10: 1 at pH 10) solution ESR spectrum. The polycrystalline ESR data (g _∥ = 2.20–2.27, g _⊥ = 2.01–2.05, and A _∥ = 120–270) of all the complexes together with the high asymmetry geometry suggest that all complexes appear to be near the static distortion (CuN₄O₂ and CuN₄S₂ chromophore geometry). The electronic spectra of the complexes involve two bands at the same intensity corresponding to a cis-distorted octahedral geometry. A common structural feature of both ligand L² and ligand L³ is that two different donor atoms at five-membered heterocyclic aromatic ring due to this N₄O₂ and N₄S₂ chromophore form stable six-membered chelate rings with metals via these two, Cu-O and Cu-S, new interactions comparatively to the first macrocyclic ligand, which has four-membered N,N′-chelate rings. The cyclic voltammetric studies point to a two-step electron transfer indicating the reduction of the two copper atoms to copper(I), i.e., Cu(III)Cu(II) ⇄ Cu(II)Cu(I) ⇄ Cu(I)Cu(0). The molar conductance for the complexes corresponds to 1: 2 and is nonelectrolyte in nature. The magnetic moment (μ_eff) of the complexes lie in the range between 1.80–1.96 μ_B. Finally, these complexes were screened for their antimicrobial activity against Aspergillus-niger of fungal strains. The text was submitted by the authors in English.     

Synthesis and investigation of the electronic structure of molybdenum tetrasulfide and its lithium intercalates

An X-ray amorphous phase of molybdenum tetrasulfide with the analytical formula MoS₄ has been sythesized. Quantum chemical modeling of the suggested local structure of MoS₄ and EHT calculation of the electronic structure of the basic (Mo₂S₄)⁴⁺ fragment are reported. The electronic structure of molybdenum tetrasulfide and its lithium intercalates was investigated by X-ray emission and X-ray photoelectron spectroscopy. It is shown that the change in the electronic structure of the starting molybdenum tetrasulfide to four lithium atoms per formula unit in the intercalate may be considered in the rigid band model. Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 37, No. 4, pp. 727–734, July–August, 1996. Translated by L. Smolina     

Electronic structure of monosubstituted benzenes and X-ray emission spectroscopy

The electronic structure of fluorobenzene was investigated by X-ray emission spectroscopy (using the F−Kα- and C−Kα-spectra) and quantum-chemical MNDO calculations. Molecular orbitals of fluorobenzene were compared with those of benzene and hydrogen fluoride. The P_π−p_π-interaction between the phenyl ring and the fluorine atom in the fluorobenzene molecule is weak for both the outer and inner π levels. For Part 2, see Ref. 1. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1454–1460, August, 1997.     

The Electronic Structure and Bonding of the First p-Block Paddlewheel Complex,Bi<Subscript>2</Subscript>(trifluoroacetate)<Subscript>4</Subscript>, and Comparison to d-Block Transition Metal Paddlewheel Complexes: A Photoelectron and Density Functional Theory Study

The photoelectron spectrum and a density functional computational analysis of the first p-block paddlewheel complex, Bi₂(tfa)₄, where tfa = (O₂CCF₃)⁻, are reported. The photoelectron spectrum of Bi₂(tfa)₄ contains an ionization band between the region of metal-based ionizations and the region of overlapping ligand ionizations that is not seen in the photoelectron spectra of d-block paddlewheel complexes. This additional ionization arises from an a_1g symmetry combination of the tfa ligand orbitals that is directed for σ bonding with the metals, and the unusual energy of this ionization follows from the different interaction of this orbital with the valence s and p orbitals of Bi compared to the valence d orbitals of transition metals. There is significant mixing between the Bi–Bi σ bond and this a_1g M–L σ orbital. This observation led to a re-examination of the ionization differences between Mo₂(tfa)₄ and W₂(tfa)₄, where the metal–metal σ and π ionizations are overlapping for the Mo₂ molecule but a separate and sharp σ ionization is observed for the W₂ molecule. The coalescing of the σ and π bond ionizations of Mo₂(tfa)₄ is due to greater ligand orbital character in the Mo–Mo σ bond (∼7%) versus the W–W σ bond (∼1%). In tribute to F. Albert Cotton for sharing the beauty of symmetry and the joy and excitement in the exploration of metal–metal bonds.     

X-ray spectral and quantum chemical analyses of the electronic structure of poly(monofluorocarbon)

The electronic structure of poly(monofluorocarbon) has been studied by X-ray spectral and quantum chemical methods. Calculations were performed in terms of the MNDO method, with the fluorographite layer modeled by clusters of different sizes. The high-resolution CK_a and FK_a spectra have been obtained; the calculated spectra are consistent with the experimental ones. It has been shown that carbon and fluorine are bonded mainly through the σ bonds. The p orbitals of fluorine atoms that are perpendicular to the C-F bond are not involved in the chemical bond, while the transitions from the molecular orbitals consisting of these p orbitals are responsible for the main maximum in the FK_a spectrum. Deceased. Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 36, No. 4, pp. 630–635, July–August, 1995. Translated by I. Izvekova     

Electronic structure and reactivity of PO 43? , P2O 74? phosphate and SO 42? , S2O 72? sulfate anions

Group-theoretical analysis and molecular orbital methods were used to obtain (in analytical form) the electronic structure and reactivity of the PO ₄ ³⁻ , SO ₄ ²⁻ and P₂O ₇ ⁴⁻ , S₂O ₇ ²⁻ anions. The reactivity of the anions is dictated by the availability of lone electron pairs on the top quasidegenerate MOs in the form of linear combinations of group orbitals from atomic orbitals (AOs) of peripheral oxygen atoms for PO ₄ ³⁻ , SO ₄ ²⁻ and the central (bridging) atom for P₂O ₇ ⁴⁻ , S₂O ₇ ²⁻ . These electron pairs are responsible for the donor-acceptor interactions during complexation, clustering, and other (addition, substitution, etc.) reactions. Original Russian Text Copyright ? 2005 V. A. Zasukha, A. P. Shpak, V. V. Trachevskii, and E. V. Urubkova __________ Translated from Zhurnal Strukturnoi Khimii, Vol. 46, No. 3, pp. 405–415, May–June, 2005.     

Free electron model in cluster structure theory. Electronic structures of [Mo6S8(CN)6]6?, [Mo6Se8(CN)6]6?, [Re6S8(CN)6]4?, and Rh6(CO)16 clusters

The results of quantum chemical calculations of the electronic structure and geometry of octahedral clusters [Mo₆S₈(CN)₆]⁶⁻, [Mo₆Se₈(CN)₆]⁶⁻, [Re₆S₈(CN)₆]⁴⁻, and Rh₆(CO)₁₆ by the ab initio SCF (RHF) and DFT (B3LYP) methods with various basis sets are presented. The electronic states of the clusters under study in ideal spherically symmetric potential were classified in the orbital quantum number l (1s, 1p, 1d, 1f, 1g, 1h, 1i), l = 0–6. In real crystal field with O_h symmetry these states are split. The calculated new electronic states were matched to the irreducible representations of the point symmetry group O_h. The polarizabilities of the compounds considered are 55–65 ų. A new model for the electronic structure of octahedral clusters containing M₆ groups was proposed. The model is based on the idea of free electrons moving in spherically symmetric potential field. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2617–2624, December, 2005.     

Theoretical Study of the Metal–Metal Interaction in Dipalladium(I) Complexes

Correlated ab initio calculations have been performed on three dipalladium(I) complexes. These compounds differ both by the metal–metal interaction and by the metal–ligand interaction. The [Pd₂Cl₂(μ −H₂PCH₂PH₂)₂] complex exhibits a σ overlap between the two binding metallic orbitals and has no bridging ligand. In [Pd₂Cl₄(μ −CO)₂]²⁻, the leading interaction between the two palladium involves a π overlap between the metallic orbitals and goes through the two bridging CO ligands. In [Pd₂Cl₂(μ −CO)(μ −H₂PCH₂ PH₂)₂], a single CO ligand bridges the two palladium atoms which interact through a hybrid σ–δ overlap. The three compounds also differ by the metal–metal distances. Surprisingly enough, while the palladium atoms are formally d ⁹ in all these complexes, none of them is paramagnetic. We propose here a detailed analysis of the electronic structures of these compounds and rationalize their chemical structures as well as the role of back-donation in the CO bridged compounds. Finally, since highly correlated treatments are used to describe these complexes, a detailed study of the role of both non-dynamical and dynamical correlations is performed. Concerning the [Pd₂Cl₄(μ −CO)₂]²⁻ complex, this analysis has revealed that the complex is not bound at the lowest correlated levels of calculation and therefore dynamical correlation is alone responsible for its binding energy.     

Structure of X-ray photoelectron and X-ray emission spectra of ThO2 and ThF4 due to electrons of molecular orbitals

The fine structure of the X-ray photoelectron and O_4,5(Th) X-ray emission spectra of the low-energy (0 …) ∼50eV) electrons of thorium in ThO₂ and ThF₄ is studied. It is established that both outer (0 … ∼15 eV) and inner (15… ∼50 eV) valence molecular orbitals, which are mostly due to the Th6p and O(F)2s shells of the neighboring thorium atoms and ligands, are formed in these compounds. Translated fromZhumal Struktumoi Khimii, Vol. 39, No. 6, pp. 1052–1058, November–December, 1998.     

S1←S0 vibronic spectrum and structure of fluoral in the S1 state

The vibronic absorption spectrum of fluoral vapor was studied in the region of the S₁←S₀ electronic transition (313–360 nm). The origin O₀ ⁰⁺) of the transition (29419 cm⁻¹) and a number of fundamental frequencies in the S₀ and S₁ states were determined. The character of intensity distribution in the spectral bands indicates that the electronic excitation leads to significant change of the CF₃ group orientation relative to the molecular frame. Moreover, it was found that the carbonyl fragment of the molecule in the S₁ state has pyramidal structure (in contrast, the carbonyl fragment of the fluoral molecule in the S₀ state is planar). The experimental torsion and inversion energy levels were used for the calculation of internal rotation and inversion potential functions of fluoral molecule in the S₁ state. The potential barriers to internal rotation and inversion were found to be 1270 cm⁻¹ (15.2 kJ mol⁻¹) and 550 cm⁻¹ (6.6 kJ mol⁻¹), respectively. The conformational changes caused by S₁←S₀ electronic excitation in the fluoral molecule are similar to those observed in acetaldehyde and biacetyl molecules and differ from the conformational behavior of hexafluorobiacetyl molecule. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 294–299, February, 1998.     

X-ray photoelectron study of the state of Ba atoms in YBa2Cu3O7−δ doped with Co and Zn atoms

Investigating changes in the charged state of atoms upon superconductivity-suppressing substitutions is one of the methods to examine a relationship between the electronic structure of HTSC materials and the transition temperature to the superconducting state. In this paper, we measured E_bnd of the inner levels of Ba atoms in Co- and Zn-doped YBa₂Cu₃O_7−δ by X-ray photoelectron spectroscopy. Upon copper substitution by Co and Zn atoms, E_bnd of the inner levels diminishes for Ba atoms but remains the same for Cu and O atoms. The change of E_bnd of the inner levels of Ba atoms is attributed to the change of the Fermi level position in the “anionic” sublattice of (Cu₃O_7−δ)⁷⁻. Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 35, No. 4, pp. 91–95, July–August, 1994. Translated by L. Smolina     

Electronic structure and properties of the ground state of copper in semiconducting cuprates

The spin-polarized discrete variational X_a method is used to calculate clusters that model the electronic structures of CuO, La₂CuO₄, and Nd₂CuO₄. It, is shown that in each of the compounds the unoccupied portion of the valence band involves mainly the O2p states, the contributions from the Cu3d orbitals being significantly smaller. The effects of the nature of holes in the valence band and of the structure of the close environment of copper on the low-energy CuK spectra and the X-ray photoelectron spectra of the above systems are discussed. Institute of Solid State Chemistry, Ural Branch, Russian Academy of Sciences. Translated fromZhumal Struktumoi Khimii, Vol. 36, No. 4, pp. 636–643, July–August., 1995. Translated by I. Izvekova     

Crystal and molecular structure of (1S,2S,4aS, 8aS)-N-(N-allyldiaminomethanethione)-1-(2-hydroxy-2,5,5,8a-tetramethyldecahydronaphthalenyl) acetamide

Crystal and molecular structure of a new homodrimanic compound (1S,2S,4aS, 8aS)-N-(N-allyldiaminomethanethione)-1-(2-hydroxy-2,5,5,8a-tetramethyldecahydronaphthalenyl) acetamide has been determined by X-ray diffraction analysis. The crystal is monoclinic, unit cell parameters are: a = 9.577(2) Å, b = 7.414(1) Å, c = 16.856(3) Å; β = 94.83(3)°, space group P2₁, Z = 2, of composition C₂₀H₃₅N₃O₂S. Two cyclohexan fragments have ordinary structure and chair-configuration typical of this compound class in homodrimanic skeleton. Ethanol molecule is located in the outer sphere. The withdrawal of carbon atoms from planar fragments of cyclohexan rings varies within the limits from 0.722(5) Å to − 0.634(5) Å. A dihedral angle between the mean-square planes of the latter equals 16.0(2)°, torsion angle (5)-(5)-(10)-(16) 171.0(1)° indicates their trans-joint. In the side non linear chain allyl group is connected to terminal nitrogen atom of thiosemicarbazide molecule. Intermolecular hydrogen bonds between carbonyl atom of acetamide fragment, ethanol molecule, and donor-acceptor groups of thiosemicarbazide moiety play the main part in crystal structure organization. Original Russian Text Copyright ? 2005 by E. P. Styngach, S. T. Malinovskii, L. P. Bets, L. A. Vlad, M. Gdanets, and F. Z. Makaev __________ Translated from Zhurnal Strukturnoi Khimii, Vol. 46, No. 4, pp.785–789, July–August, 2005.     

Synthesis, Crystal Structure, Photophysical Properties, and DFT Calculations of a Bis(tetrathia-calix[4]arene) Tetracadmium Complex

Abstract  

Thiacalix[4]arenes are a unique family of polydentate ligands that offer a combination of four soft sulfur atoms together with four hard phenol oxygen atoms for binding to metal ions. In this study, the tetranuclear cadmium (II) complex Cd₄^II(tca)₂·1.5CH₂Cl₂ (tca⁴⁻ = tetra-anionic p-tert-butylthiacalix[4]arene) (1) was synthesized by reaction of a deprotonated p-tert-butylthiacalix[4]arene and various Cd^II salts. The structure of 1 was established by single crystal X-ray diffraction analysis. The neutral complex 1 contains a square arrangement of four cadmium (II) ions sandwiched between two tca⁴⁻ ligands that have a ‘cone’ conformation similar to that of the free ligand. The absorption and emission properties of the free ligand H₄tca and complex 1 have been recorded and explained by DFT calculations of the molecular orbitals and electronic transitions between them.     

Synthesis of mixed-ligand managanese(II) complexes with alkyl xanthate ions and nitrogen-containing heterocycles. Crystal and molecular structure of the [Mn(S2COC3H7−i )2(2,2′-Bipy)] complex

We have synthesized high-spin mixed-ligand Mn²⁺ complexes Mn(S₂COR)₂L where R=i−C₃H₇, i−C₄H₉; [L=1,10-phenanthroline (Phen), 2,2′-bipyridyl (2,2′-Bipy), 4,4′-bipyridyl (4,4′-Bipy)]. As solids, the compounds are stable to oxidation by atmospheric oxygen. An X-ray structural study of the [Mn(S₂COC₃H₇−i)₂(2,2′-Bipy)] complex was carried out. The structure is composed of discrete monomeric molecules. The corrdination polyhedron of the Mn atom is a distorted [4S+2N] octahedron. The molecules are bonded by van der Waals interactions. Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 35, No. 2, pp. 106–111, March–April, 1994. Translated by T. Yudanova     

Electronic Structure and Molecular Properties of the Mixed Rhenium–Molybdenum [Re6−x Mo x S8(CN)6]q−, (x = 0 to 6) Clusters

Relativistic density functional calculations including scalar and spin-orbit effects via the ZORA approximation and including solvent effects were carried out on the [Re₆S₈(CN)₆]⁴⁻, [Re₅MoS₈(CN)₆]⁵⁻, [Re₄Mo₂S₈(CN)₆]⁵⁻, [Re₃Mo₃S₈(CN)₆]⁵⁻, [Re₂Mo₄S₈(CN)₆]⁵⁻, [ReMo₅S₈(CN)₆]⁵⁻ and [Mo₆S₈(CN)₆]⁶⁻ clusters. By increasing the replacement of each Re atom with Mo atoms we find that for x > 2 the HOMO–LUMO gap decreases significantly. The calculated gap of the [Re₃Mo₃S₈(CN)₆]⁵⁻, [Re₂Mo₄S₈(CN)₆]⁵⁻ and [ReMo₅S₈(CN)₆]⁵⁻ clusters is similar to the calculated and observed gap of the superconducting PbMo₆S₈ Chevrel phases. The current calculations also indicates that the electronic similarities of the lowest excited states of the semiconducting 24e [Re₅MoS₈(CN)₆]⁵⁻ and 23e [Re₄Mo₂S₈(CN)₆]⁵⁻ clusters with the strongly luminescent 24e [Re₆S₈(CN)₆]⁴⁻ cluster, suggest that these mixed metal clusters might be luminescent.     

S 1 ←S 0 vibronic spectrum and the structure of the chloral molecule in theS 1 stateS 0 vibronic spectrum and the structure of the chloral molecule in theS 1 state

The vibronic absorption spectrum of chloral (CCl₃COH) vapors is studied in the region of S₁ ← S₀ electron transition (32,000–28,700 cm⁻¹). The 29,070 cm⁻¹ vibronic transition (not observed because of low intensity) is believed to be the ‘start’ of the electron transition. Several fundamentals are found in the S₀ and S₁ states. Inversion splitting of the zero vibrational level in the S₁ state of chloral, indicating a nonplanar structure of the carbonyl fragment, is found. The intensity ratio of the torsional transition bands indicates that the S₁ ← S₀ electronic excitation of the chloral molecule causes significant changes in the orientation of the −CCl₃ group relative to the molecular framework. The potential functions of internal rotation (S₀ and S₁ states) and inversion (S₁ state) of the chloral molecule are determined from experimental data. The potential barriers of internal rotation (S₀ and S₁ states) and inversion (S₁ state) are 380, 780, and 760 cm⁻¹ (4.5, 9.3, and 9.1 kJ/mole), respectively. M. V. Lomonosov Moscow State University. Translated fromZhurnal Strukturnoi Khimii, Vol. 39, No. 3, pp. 507–513, May–June, 1998.     

Electronic structure and properties of isolectronically substituted compounds Y1Ba2−m M m Cu3O7 and Y1Ba2−m M m Cu4O8 (M=Be,Mg, Ca,Sr, Ba,Ra)

According to cluster calculations, the electronic structures of compounds based on Y₁Ba₂Cu₃O₇ and Y₁Ba₂Cu₄O₈ with isoelectronically substituted barium have some qualitative distinctions. These compounds behave differently upon barium substitution by other elements due to differences in the character of their highest occupied and lowest unoccupied molecular orbitals. Substitution of barium by radium is expected to lead to an increase in oxygen stability without a significant decrease in the critical temperature of superconduction transition T_s. In order to raise T_s, it is of interest to study the systems YBa_2−m(Be or Mg)_mCu₃O_x and YBa_2−m(Ca, Sr)_mCu₃O_x. On partial substitution of barium by calcium in YBa₂Cu₄O₈, the mechanism of T_s elevation may involve contraction of the forbidden band due to oxygen sublattice distortions in the vicinity of Ba centers. D. I. Mendeleev Russian Chemical Engineering University, Novomoskovsk Branch. Translated fromZhurnal Strukturnoi Khimii, Vol. 35, No. 2, pp. 24–31, March–April, 1994. Translated by O. Kharlamova     

Joint X-ray spectroscopic and quantum-chemical study of the electronic structure of pentafluorophenylalkyl ethers

The high resolution X-ray emission O-Kα spectra of pentafluorophenylalkyl ethers C₆F₅OR (R=Et, Prⁱ, and Bu^t) exhibit differences related to a change in the electronic structure of the compounds as R is varied. The search for stable conformers was performed by the semiempirical PM3 method. The most probable structures of C₆F₅OR were determined by the comparison of the experimental and theoretical X-ray spectra plotted for each conformer usingab initio calculations in the 6–31 G basis set. Substituent R in pentafluorophenylalkyl ethers is situated outside of the ring plane. The fluorination of the benzene ring changes the energy level of the lone electron pair of oxygen relative to the levels of orbitals of the ring and substituent R and leads to an increase in the efficiency of interactions in the σ-system. Deceased. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2443–2450, December, 1998.