Theoretical Study on the Structures and Electronic Spectra of the Derivatives of C_(60)-P-2,4,6-Triphenyl Borazinc

1 INTRODUCTION The electron-transfer reaction of C60 derivatives, especially light-induced electron-transfer reaction, has been an active research field for a long time. Many researches are focused on the long-live charge- separated state caused by electron-transfer[1]. And several electron-transfers between electron donor and C60 or intramolecular electron-transfer have been confirmed. As an example, TTF-C60 is proved to be a short-live charge-separated compound[2].Due to the excelle…     

Determination of Rate Constants and Inhibition Coefficients of the Stabilizer SO-3 and Functional Derivatives of the ω-(4-Hydroxyaryl)alkyl Series

Antioxidative properties of ten inhibitors of the -(4-hydroxyaryl)alkyl type were studied in a model reaction of the initiated oxidation of ethyl oleate in chlorobenzene. The rate constants k ₇ and the inhibition coefficients f were determined. All studied inhibitors are characterized by close values of the k ₇ constants, (2.6–3.7) × 10⁴ l mol^–1 s^–1, but differ in the values of inhibition coefficients. A relationship between the structures of the test compounds and their inhibiting activity is discussed.     

IR Study of Monomer–Dimer Self-association of 2,2-Dimethyl-3-ethyl-3-pentanol in n-Octane: Determination of the Molar Absorptivities of Monomer and Dimer Bands, and Dimerization Constants Using Novel Equations

The monomer–dimer self-association equilibrium of 2,2-dimethyl-3-ethyl-3-pentanol in n-octane has been studied by IR spectroscopy at four temperatures (288, 298, 308, and 318 K). The solute was chosen to restrict the self-association between solute molecules to dimerization only, owing to steric hindrance of the bulky chains in the vicinity of the OH group. Two linear equations have been derived for the treatment of the experimental data. One of these equations was used to treat the data of the concentration dependent integrated absorbance of the monomer bands for each temperature to obtain the monomer molar absorptivity, ε _m, and dimerization constant, K. The other equation was used to treat the data of concentration-dependent dimer bands to obtain the dimer molar absorptivity, ε _d, and K. Thus, the dimerization constant was determined by two methods. Since the same thermodynamic quantity K is obtained from either the monomer bands or the dimer bands, the difference between them at a given temperature can serve as an assessment of the quality of the experiment. The standard enthalpy and entropy of dimerization were also obtained from a van’t Hoff plot.     

Variation of radiative lifetimes of NH2(Ã2A1) with rotational levels in the (0, 8, 0) and (0, 9, 0) vibration bands

Radiative lifetimes from the first electronically excited state of the amidogen free radical, NH(2)(A?(2)A(1)), are reported for rotational states in selected vibrational levels ν(2)' using laser-induced fluorescence. Thermal collision of argon, Ar(?)((3)P(0), (3)P(2)) metastable atoms in a microwave discharge-flow system with ammonia (NH(3)) molecules produced ground state NH(2)(X?(2)B(1)). The radiative lifetimes for the deactivation of NH(2)(A?(2)A(1)) were determined by measuring the decay profiles of NH(2)(A?(2)A(1)?→?X?(2)B(1)). In addition to the Fermi resonances with the ground state that lengthen the radiative lifetimes, a systematic increase in the radiative lifetimes with rotational quantum number was observed. Furthermore, the average radiative lifetimes of the (0, 9, 0) Γ, τ(1) = 18.65 ± 0.47 μs and (0, 8, 0) Φ, τ(2) = 23.72 ± 0.65 μs levels were much longer than those of the (0, 9, 0) Σ, τ(3) = 10.62 ± 0.47 μs, and (0, 8, 0) Π, τ(4) = 13.55 ± 0.55 μs states suggesting increased mixing of the first electronic excited and the ground states.     

Co-crystal of (R,R)-1,2-cyclohexanediol with (R,R)-tartaric acid,a key structure in resolution of the (±)-trans-diol by supercritical extraction,and the related ternary phase system

A novel co-crystal of trans-(R,R)-1,2-cyclohexanediol and (R,R)-tartaric acid (with 1:1 molar ratio, 1) has been found to be a key crystalline compound in the improved resolution of (±)-trans-1,2-cyclohexanediol by supercritical fluid extraction. The molecular and crystal structure of this co-crystal, which crystallizes in orthorhombic crystal system (space group P2₁2₁2₁, a = 6.7033(13) Å, b = 7.2643(16), c = 24.863(5), Z = 4), has been solved by single crystal X-ray diffraction (R = 0.064). The packing arrangement consists of two dimensional layers of sandwich-like sheets, where the inner part is constructed by double layers of tartaric acids which hydrophilicity is “covered” on both upper and bottom side by cyclohexanediols with the hydrophobic cyclohexane rings pointing outward. Thus, a rather complex hydrogen bonding pattern is constructed. The relatively high melting point (133 °C) observed by both simultaneous TG/DTA and DSC, and the main features of FTIR-spectrum of 1 are explained by the increased stability of this crystal structure. DSC studies on binary mixtures of co-crystal 1 with (R,R)-1,2-cyclohexanediol or (R,R)-tartaric acid, revealed eutectic temperatures of T_eu = 100 or 131 °C, respectively. Between (S,S)-1,2-cyclohexanediol and (R,R)-tartaric acid a eutectic temperature of T_eu = 85 °C have also been observed. The phase relations have been confirmed by powder X-ray diffraction, as well.     

Factors affecting the lability of the σ(M-X) bond in cycloplatinated and cyclopalladated complexes containing [C(sp, ferrocene),N,X] or [C(sp, phenyl),N,X] (X = S, N) terdentate ligands

The reactions of the cyclometallated complexes [M{[(η⁵-C₅H₃)-CHN-(C₆H₄-2-SMe)]Fe(η⁵-C₅H₅)}Cl] [with M = Pt (5a) or Pd (5b)] with PPh₃ under different experimental conditions are reported. These studies have allowed the isolation of [M{[(η⁵-C₅H₃)-CHN-C₆H₄-2-SMe]Fe(η⁵-C₅H₅)}(PPh₃)]X [M = Pt and X⁻ = Cl⁻ (6a) or (7a) or M = Pd and X⁻ = Cl⁻ (6b) or (7b)] and the neutral complex [Pd{[(η⁵-C₅H₃)-CHN-(C₆H₄-2-SMe)]Fe(η⁵-C₅H₅)}Cl(PPh₃)] (8b). In 6-7a,b the ferrocenyl Schiff base behaves as a [C(sp², ferrocene),N,S]⁻ group while in 8b it acts as a [C(sp², ferrocene),N]⁻ ligand. The X-ray crystal structure of 7b confirms the mode of binding of the ferrocenyl ligand. The comparison of the results obtained and those reported for [M{(C₆H₄)-CHN-(CH₂-CH₂-2-SEt)}Cl] and [M{(C₆H₄)-CHN-(C₆H₄-2-SMe)}Cl] {with a [C(sp², phenyl),N,S]⁻ terdentate ligand} or [M{[(η⁵-C₅H₃)-CHN-(CH₂)₃-NMe₂]Fe(η⁵-C₅H₅)}Cl] {in which the ligand acts as a [C(sp², ferrocene),N,N′]⁻ group} have allowed the elucidation of the relative importance of the factors affecting the lability of the M-X (X = S or N′) and M-Cl bonds in cyclometallated compounds with [C,N,S]⁻ and [C(sp², ferrocene),N,X]⁻ ligands.     

Regio- and Diastereoselectivity in the Thiomethylation of α-(1-Hydroxyalkyl)acrylate Derivatives

The regio-and diastereoselectivity of reactions of selected α-(1-hydroxyalkyl)acrylate derivatives with sodium methanethiolate have been investigated. The hydroxy compounds typically undergo conjugate addition with up to 66% d.e., while the acetoxy and bromo analogues favour S_N' and S_N reactions, respectively.     

Study of η5-(1-chloro-4-methylcyclohexadienyl) and η5-(1-methyl-4-chlorocyclohexadienyl)tricarbonylmanganese complexes in solution and in the solid state

The spectroscopic studies of neutral η⁵-(1-chloro-4-methylcyclohexadienyl) and η⁵-(1-methyl-4-chlorocyclohexadienyl) tricarbonylmanganese complexes have been realized in solution by ¹H NMR spectroscopy as well as in the solid state. The structures showed a dihedral angle of the sp³ carbon of 33.2° and 36.6° with respect to the cyclohexadienyl ring. To cite this article: F. Rose-Munch et al., C. R. Chimie 6 (2003).     

Electronic structure of the surface compounds ≡SiOElCl3 (El, = C,Si, Ge,Sn) and their thermal stability

The SCF MO LCA0 method in the MNDO approximation has been used to consider the electronic structure of the surface compounds SlODlCl₃ (El = C, Si, Ge, Sn), modelled by extended clusters. The thermal stabilities of these groups are compared and conclusions ore drawn about the probable mechanism of the interaction of the surface silanol groups of SiO₂ with ElCl₄ molecules.Institute for Surface Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 27, No. 1, pp. 19–22, January–February, 1991. Original article submitted March 11, 1990.     

Bis-trifluoromethyl Effect: Doubled Transitions in the Rotational Spectra of Hexafluoroisobutene, (CF(3))(2)C═CH(2)

Rotational spectra for hexafluoroisobutene, and its (13)C isotopologues, have been recorded between 8 and 16 GHz using a chirped pulse, Fourier transform microwave spectrometer. Notably, all spectra observed are doubled with separations between the doublets being between 1 and 60 MHz. We propose that the bis-trifluoromethyl groups of the target molecule are staggered in the equilibrium configuration, and that a novel, out-of-phase rotation through a F-CCC-F planar configuration with low barrier (<100 cm(-1)), leads to the observed doubled rotational spectra.     

The Effect of Temperature on the Equivalent Conductivities and Ion-Association Constants of Some Tris-(ethylenediamine)chromium(III) Complexes in N,N-dimethylformamide and N,N-dimethylacetamide

The equivalent conductivities of tris-(ethylenediamine)chromium complexes, [Cr(en)₃]X₃ (where X⁻= Cl⁻, Br⁻, I⁻; en = ethylenediamine) were measured as functions of temperature (278.15 to 328.15 K) and concentration [(1.948 ×10⁻⁴ to 10.728 ×10⁻⁴ mol⋅dm⁻³) and (2.282 ×10⁻⁴ to 11.246 ×10⁻⁴ mol⋅dm⁻³)] in N,N-dimethylformamide (DMF) and N,N-dimethylacetamide (DMAC), respectively. Equivalent conductivity values for [Cr(en)₃]X₃ in DMF were found to be higher than those in DMAC. The conductivity data were analyzed with the Robinson-Stokes equations. For [Cr(en)₃]X₃, the limiting equivalent ionic conductivities of [Cr(en)₃]³⁺ and the ion-association constants (K _A) of the ion-pair between [Cr(en)₃]³⁺ and the monovalent halide anions were determined in DMF and DMAC. The values of K _A for three complex salts in DMF were higher than those in DMAC. This can be ascribed to an increase of the ion-association constants with a decrease of the relative permittivity of the solvents. The values of K _A at 298.15 K decreased in the order Cl⁻> Br⁻> I⁻ in DMF and Cl⁻> I⁻> Br⁻ in DMAC. The K _A values for [Cr(en)₃]Cl₃ increased with increasing temperature in both DMF and DMAC. For [Cr(en)₃]X₃(X⁻= Br⁻, I⁻) in both solvents, this indicates increasing disorder occurs with increasing temperature. Thermodynamic parameters (standard Gibbs energy, enthalpy and entropy changes) were determined from the temperature dependence of K _A in DMF and DMAC. These parameters were inter-compared in their dependences on temperature and solvent.     

Homogeneous and Solid-Gas Hydrogenation of Alkynes in the Presence of the Clusters Fe3(CO)9(ε-RC2 R 1) {R=R 1=Ph, Et; R=Me, R 1=Ph}: Characterization of New Metallacyclic Derivatives

The clusters Fe₃(CO)₉(RC₂ R ¹) (R=R ¹=Ph, Et; R=Me, R ¹=Ph), complexes 1a, 1b, 1c, containing an alkyne bound in perpendicular fashion with respect to a cluster edge, catalyze the hydrogenation of some acetylenes either under homogeneous and solid–gas conditions. We hypothesize that cluster catalysis occurs and that the catalytic activity is related to the coordinating ability of the alkynic substrates. Competition between hydrogenation and formation of metallacyclic byproducts occurs. The new metallacyclic derivatives Fe₃(CO)₆(-CO)₂{(RC₂ R ¹)(R ²C₂ R ³)}, Fe₂(CO)₆{(RC₂ R ¹)(R ²C₂ R ³)} {R=R ¹=Et, R ²=R ³=H, Ph; R ²=Me, R ³=Et, Ph; R ²=H, R ³=Bu ^t . R=R ¹=Ph, R ²=Me, R ³=Et, Ph} (complexes 2, 3) were found both in the homogeneous reaction mixtures and after the solid–gas reactions. The formation of these products lowers the catalytic activity.     

1H,13C,and19F NMR study of products of the interaction of the η5-cyclopentadienyldicarbonyliron(ii) anion,CpFe(CO)2 −, with pentafluorobenzoyl chloride

Interaction of the ⁵-cyclopentadienyldicarbonyliron(II) anion with pentafluorobenzoyl chloride affords C₆F₅COFe(CO)₂Cp, CpFe(CO)₂C₆F₄COFe(CO)₂Cp, and CpFe(CO)₂C₆F₄C₆F₄Fe(CO)₂Cp. The reaction products are characterized by¹H,¹³C and¹⁹F NMR spectra.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 935–937, May, 1994.     

Ab Initio Calculations on Nitramide and Its Methyl Derivatives( Ⅱ )——The Harmonic Force Fields and Vibrational Spectra of Nitramide and Its Isotopic Derivatives

The harmonic force field and the vibrational spectrum of nitramide were calculated by using the ab initio gradient program TEXAS at the Hartree-Fock level with a 4-21G basis set. The directly computed theoretical harmonic force field was scaled by using empirical scale factors which are transferred from other molecules and provided an a priori prediction of fundamental frequencies and intensities. The average deviations between predicted vibrational frequencies of nitramide and experimental IR spectrum in an argon matrix are 63 cm-1 for symmetric vibrations and 41 cm-1 for antisymmetric modes. A new set of scale factors was optimized in this paper. These scale factors reduced the average deviations to 2. 3 cm-1 for symmetric modes and 0. 8 cm-1 for antisymmetric ones. The vibrational spectra of three isotopic derivatives of nitramide were predicted by using the force field resulted from the optimized set of scale factors, which are in good agreement with their experimental data in an argon matrix.     

Structural and thermodynamic data on the pseudobinary phases R(Co1−xCux)5 WITH R ≡ Sm,Y, Ce

For the phases R(Co_1−itxCu_itx)₅ with R ≡ Sm, Y, Ce, homogenized at 950 °C, the enthalpies of formation were determined by a calorimetry technique involving dissolution in molten tin and the lattice parameters were measured using X-ray diffraction in a focusing camera. In order to study the effect of substitution of cobalt for copper, the lattice parameters were corrected for the contribution of the departure of R from stoichiometry. For the R(Co_1−itxCu_itx)₅ phases with R ≡ Sm, Y, the lattice parameters were also measured after heat treatment at 400 °C. The x dependences of the enthalpies of formation and lattice parameters indicate an ideal behaviour for the mixing of SmCo₅ and SmCu₅ on one hand, and for YCo₅ and YCu₅ on the other hand. This result is consistent with the homogeneous state found for Sm(Co_1−itxCu_itx)₅ and Y(Co_1−itxCu_itxon the whole x range at 400 °C. For the mixture of CeCo₅ and CeCu₅, the enthalpies of formation exhibit a slightly positive deviation which predicts the solid state miscibility gap previously evidenced in the CeCo₅-CeCu₅ section below 800 °C.     

The Study of the Reaction Mechanism for the Dehydrogenation of Ethylbenzene on Iron Oxide Catalysts (Ⅰ)——IR Spectra of Adspecies and Kinetic Isotope Effects

In situ PT-IR spectroscopy was used to examine ethylbenzene adspecies on iron-oxide-besed catalysts,and the method of kinetic isotope effects was used to investigate the rate determining step of the dehydrogenation.A possible reaction mechanism is proposed.     

Synthesis and characterization of stable osmafuran starting from HC≡CCH(OH)C≡CH and OsHCl(CO)(PPh3)3

This paper presents a new convenient route to prepare osmafuran starting from readily accessible HC≡CCH(OH)C≡CH and OsHCl(CO)(PPh₃)₃. Treatment of a solution of OsHCl(CO)(PPh₃)₃ in dichloromethane with HC≡CCH(OH)C≡CH, followed by the addition of acetic acid, produced osmafuran [Os(CHC(PPh₃)CO(CH₂CH₃))Cl(CO)(PPh₃)₂]Cl (2). 2 has been isolated in good yield and fully characterized. ¹H and ¹³C NMR spectra show the characteristic downfield chemical shifts of the ring hydrogen and carbon atoms. NMR and X-ray diffraction data provide strong evidence for the aromatic nature of 2. Probably due to the effect of the phosphonium substituent, 2 exhibits remarkable thermal stability, air stability and lower reactivity.

     

Complexes of Zn(II) and Сu(II) with the Amino Derivatives of Deoxycholic Acid: Syntheses,Structures, and Properties

Russian Journal of Coordination Chemistry - Complexes [Zn(L)Cl2] (I), Cu(L)Cl2 ? H2O (II), Zn(L1)Cl2 ? 0.5H2O (III), and Cu(L1)Cl2 ? 0.5H2O (IV) (where L and L1 are the...