NMR and IR spectroscopic study of the structure of quaternary salts of 1-vinylpyrazoles

Conclusions IR and NMR spectral analysis indicated that quaternization of 1-vinylpyrazoles leads to a decrease in conjugation between the heterocycle and the vinyl group and to a significant leveling out of the charges on the atoms in the heterocycle and vinyl group.DeceasedTranslated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1007–1012, May, 1985.     

NMR Spectra and structure of 1-vinylpyrazoles

Conclusions A¹H and¹³C NMR spectral analysis permitted evaluation of electronic and steric effects in 1-vinylpyrazoles. 5-Methyl-1-vinylpyrazoles have predominantly S-cis-N² orientation, while 1-vinylpyrazoles without substituents at C⁵ are conformer mixtures.Deceased.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1012–1018, May, 1985.     

Bromination of 1-vinylpyrazoles

In addition to the principal reaction pathway — addition of bromine to the double bond of the vinyl group — in the bromination of 1-vinylpyrazoles, the hydrogen atom in the 4 position of the pyrazole ring undergoes substitution, and the liberated hydrogen bromide coordinates with the pyrazoles present in the reaction mixture.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 960–962, July, 1978.     

Rotational isomerism in 1-vinylpyrazoles and 1-vinylimidazoles from 1H and 13C NMR data and quantum-chemical calculations

A quantitative evaluation of the percentages of rotational isomers of 1-vinylpyrazoles and 1-vinylimidazoles was made on the basis of an analysis of the ¹H and ¹³C NMR spectral parameters and quantum-chemical calculations. It is shown that the populations of the s-cis-(N₍₂₎, N₍₃₎) and s-trans-(N₍₂₎, N₍₃₎) forms in both the 1-vinylpyrazole and in the 1-vinylimidazole are approximately equal.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1346–1351, October, 1990.     

The crystal and molecular structure of acetonitrilechlorodicyclopentadienyltitanium tetrachloroferrate(III). Some Mössbauer and X-ray photoelectron spectroscopic data

Summary The title compound crystallizes in the orthorhombic space group P2₁2₁2₁ with Z=4 and lattice parametersa=1744.2(4),b=1360.7(4),c=751.3(5) pm. An x-ray analysis shows the compound to consist of discrete (h⁵-C₅H₅)₂-Ti(Cl)NCMe⁺ cations and FeCl ₄ ^– anions. The cation has a distorted tetrahedral structure (Ti-C: 231.9-237.6 pm; Ti-Z: 203 and 204pm; Ti-Cl: 230.4 pm; Ti-N: 213.5 pm; Z-Ti-Z: 133.2°; Cl-Ti-N: 91.7° (Z: centre of cyclopentadienyl ring). The relatively short Ti-Cl bond length indicates a modest Ti-Cl -bonding contribution. The tetrachloroferrate(III) anion possesses a nearly undistorted tetrahedral geometry (Fe-Cl: 216.0–218.5 pm; Cl-Fe-Cl: 109.0–111.1°). Mössbauer and x-ray photoelectron spectroscopic data confirm the crystallographically derived structural features.     

Interaction of 1-vinylpyrazoles with alkanethiols

It was found that vinylpyrazoles react with thiols both according to ionic and according to free-radical mechanisms, with the formation of products of - and -addition. Radical thiylation of 1-vinylpyrazoles is a convenient method of synthesis of pyrazoles with sulfur-containing substituents.Institute of Organic Chemistry, Siberian Branch, Russian Academy of Sciences, 664033 Irkutsk. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 8, pp. 1874–1878, August, 1992.     

Reaction of 1-vinylpyrazoles with tetracyanoethylene

It was shown that in the reaction of tetracyanoethylene with 1-vinylpyrazoles in aprotic solvents, one of the first stages involves the formation of - complexes. The final products of the reaction are 1-(2,2,3,3-tetracyano-1-cyclobutyl)pyrazoles.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 924–926, July, 1989.     

Molecular structure of bismuth trichloride from combined electron diffraction and vibrational spectroscopic study

The results of an electron diffraction reanalysis, augmented with a combined electron diffraction and vibrational spectroscopic elucidation, of the molecular structure of BiCl₃ are reported. The principal parameters arer _g (Bi-Cl)=2.424±0.005 å (r =2.417±0.005 å) and <Cl-Bi-Cl=97.5±0.2. They are in excellent agreement with previous electron diffraction analysis [1], utilizing a more limited data range from the same experiment. They are also fully consistent with the expected trends of geometrical variation in the Group V trihalide series. The force fields of BiCl₃, determined by normal coordinate analysis and by combined analysis, agree within experimental error.     

Molecular structure of 3-methylthiophene studied by gas electron diffraction combined with microwave spectroscopic data

The molecular structure of 3-methylthiophene

has been determined by gas electron diffraction (GED) combined with microwave (MW) spectroscopic data. Ab initio calculations at the HF/3–21G* level were carried out and used as structural constraints in the data analysis. The torsional vibration of the methyl group was treated as a large-amplitude motion. The structural parameters were determined to be: r_g(S---C₂) = 1.719(2) Å, r_g(C₂=C₃) = 1.370(3) Å, r_g(C₃---C₆) = 1.497(6) Å, r_g(C₂---H) = 1.101(5) Å, CSC = 91.6(2)°, SC₂C₃ = 113.3(5)°, SC₅C₄ = 111.3(3)°, C₂C₃C₆ = 123.2(11)° and C₃C₆H = 112(2)°. The values of r(S---C₂) − r(S---C₅) and r(C₂=C₃) − r(C₄=C₅) were fixed at the 3–21G* value of 0.002Å. Parenthesized values are the estimated limits of error (3σ) referring to the last significant digit.     

Effective charges on atoms of β-diketonates of metals obtained from x-ray electron spectroscopic data

Physicotechnical Research Institute of the Far Eastern State University. Translated from Zhurnal Strukturnoi Khimii, Vol. 30, No. 3, pp. 144–147, May–June, 1989.     

X-ray photoelectron spectroscopic studies of solid electrolytes

A study of solid electrolytes by X-ray photoelectron spectroscopy reveals that silver (I) and copper (I) compounds generally show very small shifts in electron binding energies. The complex crystal structure of the β-aluminas, however, gives rise to different cation sites which can be distinguished by this technique. Calculations of self-potential show the importance of this term for determining shifts. The possibility of determining the partial ionic charge from the measured shift is also considered.     

Predictive modeling of electrocatalyst structure based on structure-to-property correlations of x-ray photoelectron spectroscopic and electrochemical measurements

Chemical structure and catalytic activity of nonplatinum porphyrin-based electrocatalyst for oxygen reduction is characterized by combination of X-ray photoelectron spectroscopy (XPS) and rotating disk electrode. The goal of the study is to show how modifications in the molecular structure affect catalytic characteristics and how to use these structural modifications in a purposeful manner to increase catalytic activity. Initial correlation of structure to electrochemical performance is achieved through the application of principal component analysis (PCA) to curve-fits of high-resolution XPS spectra combined with results of electrochemical measurements. Furthermore, a predictive model that describes this correlation is build using the combination of genetic algorithm (GA) and multiple linear regression (MLR). Based on structure-to-property correlations, two types of active sites responsible for the catalytic activity, i.e., Co associated with pyropolymer and Co particles covered by oxide layer, are determined, and a dual-site for oxygen reduction on cobalt porphyrins is hypothesized, allowing for designing a catalyst structure with optimal performance characteristics.     

X-ray photoelectron spectroscopic study of tetraphenyldithiapyranylidene and its polyiodides

High resolution X-ray photoelectron spectra are reported for tetraphenyldithiapyranylidene (DIPSσ₄), three of its polyiodides, and its diperchlor allows to emphasize the evolution of the structure with iodine contents. The chemical nature of the iodine species is also inferred from the I3d_{$\text{5}\text{2}$} signal shape. The low binding energy of the highest occupied molecular orbital is compared to that of other π-systems, and the Iteration of the electron delocalization is shown to be rel     

Molecular structure and force field of boron tribromide as determined from combined analysis of gas electron diffraction and spectroscopic data and supported by quantum-chemical density-functional calculations

The thermal-average parameters of BBr₃ at 21(1) °C were obtained from a conventional analysis of gas electron diffraction (GED) data (r_g(B---Br) = 190.0(4) pm). The equilibrium structure and the force constants were refined from a joint analysis of the GED intensities and vibrational frequencies using different approximations. The simplest approximation (quadratic potential function in rectilinear coordinates) is suitable for the refinements of the equilibrium bond length (r^h_e(B---Br) = 189.6(4) pm) and the force constants of BBr₃. The molecule is planar within the error limits. Quantum-chemical density-functional calculations supported planarity of the molecule.     

Conformational and spectroscopic investigation of 3-hydroxyflavone-aluminium chelates

3-Hydroxyflavone (3HF), which is the simplest molecule of the flavonol class, possesses chelating properties towards Al(III). Spectrophotometric methods have shown that the 3HF molecule forms an Al(3HF)2 complex in pure methanol. The structure of this complex, obtained by quantum semi-empirical AM1 method, indicated that complexed 3HF adopts a pyronium form. Structural and electronic modifications induced by chelation are illustrated by the important frequency shifts observed between free and complexed 3HF FT-Raman spectra and by the chemical shifts variations in the 13C NMR spectra of the two species. Complexes with the same stoichiometry were formed when AcO- or MeO- are present in the medium. However, in acidic medium the chelate composition is Al2(3HF).     

Conformational analysis of 2-oxo(thio)-1,3,2-dioxaphosphorinanes with a P-H bond from vibrational spectroscopic data

The steric structure of four 2-hydro-2-oxo(thio)-1,3,2-dioxaphosphorinane (DOP) molecules has been studied by means of Raman and IR spectroscopy. A characteristic feature of these compounds is the presence of a hydrogen atom as a "light" exocyclic substituent whose vibration is not mixed with the vibrations of the molecular skeleton.A. E. Arbuzov Institute of Organic and Physical Chemistry, Kazan Scientific Center, Russian Academy of Sciences, 420083 Kazan, Tatarstan, Russia. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 12, pp. 2725–2730, December, 1992.     

The molecular structure of pyrazine as determined from gas-phase electron diffraction data

The structure of pyrazine (1,4 diazabenzene, C₄H₄N₄) has been determined at 333 K by means of gas-phase electron diffraction. The r_g parameters are as follows: r(C-C) = 1.339 ± 0.002 Å. r(C-N) = 1.403 ± 0.004 Å, r(C-H) = 1.115 ± 0.004 Å. ∠C-C-N = 115.6 ± 0.4°, and ∠C-C-H = 123.9 ± 0.6° (error limits are 2.5σ). At a 10% level the r_α structure does not differ significantly from the structure in the solid state, so long as high order X-ray, results corrected for librational motion are used; otherwise significantly different results are found even at the 1% level. Calculated and observed mean square amplitudes compare favourably.     

HeI photoelectron spectroscopic study of the electronic structure of SSF2 and FSSF compounds

HeI photoelectron (PE) spectra are re-recorded for SSF₂ and FSSF. The assignment of bands has been made with the aid of band shapes, band intensities and ab initio calculations. In the PE spectrum of SSF₂, two sharp peaks at 10.48 and 11.22 eV are considered to result from through-space interaction of lone-pair orbitals in the two S atoms and two sharp peaks at 12.50 and 12.90 eV from through-space interaction of lone-pair orbitals in the two F atoms. The larger splitting of the S atoms can be attributed to the larger 3p orbital of S. The lack of sharp peaks in the PE spectrum of FSSF shows that there is no orbital which embodies the character of a lone-pair. So the PE spectra of SSF₂ and FSSF are examples embodying through-space interaction of lone-pair orbitals.