Hyperfine coupling constants of Mg-centered radicals and radical ions

The energies, geometric parameters, spin densities, and HFC constants of the Mg-centered radicals ^•MgH, ^•MgOH, ^•MgMe, and monovalent magnesium aqua complexes Mg(H₂O)_n ⁺ (n = 0–3) were calculated using the density functional theory. As n increases, the HFC constants decrease for Mg atoms and increase for O atoms. The theoretical HFC constants in the Mg-centered radicals are in good agreement with experimental data. Published In Russian In Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, Pp. 861–865, May, 2007.     

Ionization constants of a number of alkaloids used in medicine

The pK_a values of a number of alkaloids in water or in aqueous ethanol have been measured by the potentiometric titration method: nuphleine — 4.59, 6.98; brevicolline — 5.17, 8.02; chelidonine — 6.40; sanguinarine — 7.32; chelerythrine — 7.53; stepharine — 8.48; d-pseudoephedrine — 9.49. For nuphleine and brevicolline, each of which has two nitrogen atoms capable of protonation, assignments have been made of pK_a values to the corresponding atoms on the basis of the results of UV spectroscopy.All-Union Scientific-Research Institute of Medicinal Plants, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 337–341, May–June, 1984.     

Hyperfine interaction of the unpaired electron with nuclei in a methyl group in π-electron radicals

Hyperconjugation is applied to {ie432-01} to derive the tensors for the hyperfine interaction with the CH₃ nuclei for the case of free rotation.Read at the Symposium on Quantum Chemistry, Palanga, June 1965.     

Coupling constants in the direct configuration interaction method

A general algorithm of evaluation of the coefficients of molecular integrals (coupling constants) appearing in the direct configuration interaction method is derived. The configurations are assumed to be spin-adapted antisymmetrized products of orthonormal orbitals. No limitation is imposed either upon the reference state (the number of the singly occupied orbitals may be arbitrary) or upon the excitation multiplicity.     

13C Hyperfine interaction in the hexafluorobenzene radical anion

Naturally abundant ¹³C satellites have been detected in the isotropic EPR spectrum of C₆F^?₆, the ¹³C coupling being 12.1 G The magnitude of this coupling does not support a nonplanar structure for C₆F^?₆. Also, the value is more consistent with a σ¹ than a π¹ configuration in D_6h, symmetry.     

Ab initio rotational constants of interstellar species: Cyanoacetylene hydrogenated derivatives

By means of ab initio calculations, the rotational constants and dipole moments of H_nC₃N (n = 1, 3, 5, 7, and 9) species have been calculated at the HF / 6-31G * level of theory. Selected cases have been also calculated at the MP 2/6-31G * level and the influence of calculation level on rotational constant values is briefly discussed. Some of these species were discovered in the interstellar medium, while others have still not been detected there, although their existence is very probable. The results given here could help in their detection. © 1993 John Wiley & Sons, Inc.     

Study of the direct carbon-proton constants of the spin-spin interaction in sulfolane derivatives

Conclusions The increments of the chemical shift and spin-spin interaction constants for a series of substituents were determined based on a study of the¹³C NMR spectra of sulfolane and its 3- and 3,4-substituted derivatives. The values of the direct CSSI at C³ and C⁴ for cis-3,4-disubstituted sulfolanes with the same substituents are criteria which permit determining the steric orientation of the substituents and the isomerism of sulfolanes.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2723–2727, December, 1983.We would like to thank N. N. Novitskaya and B. V. Flekhter for supplying the sulfolane derivatives for the study.     

Hyperfine interaction in K2Ba[Fe(NO2)6

Magnetic hyperfine splitting observed in the low temperature M?ssbauer spectrum of potassium barium hexanitro ferrate(II), in the absence of any external field, is attributed to the 5T2g state of the central metal atom further split into a ground 5Eg state and a first excited 5B2g state under a distorted octahedral symmetry in contrast to the earlier prediction of 1A1g ground state on the basis of room temperature M?ssbauer spectral and other properties. The central iron atom is coordinated to six nitrito groups (NO2-), having an oxidation state of +2. The temperature dependence of M?ssbauer spectra is explained on the basis of electronic relaxation among the spin-orbit coupled levels of the 5Eg ground state. Various kinds of electronic relaxation mechanisms have been compared to explain the proposed mechanism. The observed temperature dependent spectra with varying internal magnetic field and line width can be explained by simple spin lattice relaxation.     

Determination of the steric configuration of organic compounds with the aid of stable iminoxyls

Conclusions A new method was proposed for determining the steric configuration of organic compounds, using a free radical label.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1137–1139, May, 1967.     

Electrostatic interaction between cationic calix[4]pyrroles and anionic porphyrins in water

The formation and characterization of molecular assemblies resulting from mixing of solutions of tetracationic calix[4]pyrroles and tetraanionic porphyrins in water are reported. The self-assembly of the complementary building blocks was quantitatively studied by UV–vis, ¹H NMR, Fluorescence and ESI–MS. Binding constants calculated by absorption spectroscopic titrations were in the range of 10³–10⁵ M^?1. The results indicate that the cationic thiacalix[4]pyrroles show greater binding affinity towards metal free porphyrins than metalloporphyrins under neutral conditions.