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.     

An ultraviolet photoelectron spectroscopic study of the electron states of iodine complexes with electron donors

HeI photoelectron spectra of the vapour phase complexes of diethylether and diethylsulphide with iodine have been investigated for the first time. The iodine orbital ionization energy decreases on complexation while the donor lone-pair orbital ionization energy increases markedly; the shifts are considerably larger in the sulphide complex as expected on the basis of enthalpy considerations.     

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.     

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.     

Molecular potential functions from joint analysis of gas electron diffraction and spectroscopic data

A joint analysis of electron diffraction and spectroscopic data is carried out for BF₃, PBr₃, AsBr₃, SbCl₃, SeO₂ and ClO₂ in terms of the harmonic force fields. The scheme of analysis was extended to include the following spectroscopic observables: vibrational frequencies, rotational, Coriolis coupling and centrifugal distortion constants and, whenever available, those for the isotopic species. For ClO₂ a simplified anharmonic analysis was also performed, the anharmonic spectroscopic observables being involved in this case.

Compelling evidence has been presented that the conventional harmonic approximation for the force field in terms of rectilinear internal coordinates yields the simplest satisfactory representation of diffraction and spectroscopic observations. However, a consistently better fit to experimental data was found when natural curvilinear internal coordinates were used. It is shown here that for the systems considered the joint analysis of data from various sources ensures that reliable and accurate values for equilibrium distances and force field parameters are obtained. The optimized values of spectroscopic constants, structural and force field parameters obtained are presented and compared with those available from the literature.     

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.     

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.     

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 0.002 Å. Parenthesized values are the estimated limits of error (3σ) referring to the last significant digit.     

Conformational properties and electronic structure of tetrahydrotetrazines studied by photoelectron spectroscopy and quantum chemical calculations

The photoelectron (PE) spectra of tetrahydro-1,2,3,4-tetrazines 1 and 2 and tetrahydro-1,2,4,5-tetrazines 3–5 have been recorded and their conformations have been investigated by ab initio SCF calculations. While v-tetrazine2 is planar, tetrazines 1 and 3–5 each possess two low-energy conformations, according to ab initio HF and Becke3LYP methods. Attempts to assign ionization potentials to molecular orbitals obtained by semiempirical PM3 calculations indicate that this method is not suited for the compounds studied. Best results were obtained when the ab initio hybrid method Becke3LYP of the density functional theory was employed. Two conformers of 1 and 3–5 are present in the gas phase and their PE spectra are superimposed one upon the other. For v-tetrazine1, ionizations arising from half-chair and unsymmetrical boat conformers have similar energies and cannot be separated in the PE spectrum. For s-tetrazine3, on the other hand, the spectrum clearly shows different ionizations of both half-chairs, 3ee and 3ae.     

气态肼的三种电子能谱和量子化学研究

本文应用X射线光电子能谱技术测得了气态肼的内层电子能谱、Auger电子能谱和价带电子能谱,对其电子结构进行了系统研究。又采用了不同能量的X射线为激发源,对比了Mg Ka 和 Zr M:价带能谱,定性地获得了肼的分子轨道的组成。本文对肼电子能谱进行了量子化学研究,用从头计算法给出了分子轨道波函数的成分,并指认了能谱,实验结果和计算值之间的一致性很好。     

Rapid evaluation of the Voigt function and its use for interpreting X-ray photoelectron spectroscopic data

While the Voigt function is recognized as the best function to represent the photoelectron spectroscopic process, it is less frequently used because it cannot be represented as an analytical function and thus has to be evaluated numerically. This paper shows how the true Voigt function can be calculated rapidly with approximately the same speed as pseudo-Voigt functions by using approaches that have been used by the astronomical sciences community. The Voigt function is calculated using code previously published by Wells. The paper describes a method for calculating the function to generate photoelectron peaks for curve fitting X-ray photoelectron spectroscopic data. An appendix is provided with the listing of a Fortran 90 program which uses the subroutine HUMDEV published by Wells. Examples of using this approach for the fitting of experimental core X-ray photoelectron spectroscopic data are presented, and the fits compared with fits using a pseudo Voigt product function. The use of the true Voigt function in the calculation of spectra in the core and valence band region is also described and illustrated by comparing the calculated spectra with experimental spectra.     

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.