Measurement of the differential cross section and of the tensor and vector analyzing powers for the fragmentation of 4.5-GeV/c deuterons on beryllium in the reaction involving proton emission at an angle of 80 mrad

The invariant differential cross section, the tensor analyzing power A _yy , and the vector analyzing power A _y for the reaction ⁹Be(d, p)X are measured at an initial deuteron momentum of 4.5 GeV/c and a proton detection angle of about 80 mrad. The data obtained for the differential cross section are consistent with the results of measurements at 3.5 and 5.78 GeV/c and a proton emission angle of 2.5°. The values found for the tensor analyzing power A _yy are compared with similar data obtained previously for the deuteron-fragmentation process occurring on a carbon target at various values of the initial deuteron momentum and leading to proton emission at zero angle. The data on the differential cross section for the reaction ⁹Be(d, p)X can be satisfactorily described within the relativistic impulse approximation by using standard deuteron wave functions; however, the approach based on this conceptual framework proves to be inadequate in dealing with data on the tensor analyzing power. These results indicate that it is necessary either to change the method for describing the relativistic deuteron or to take into account additional mechanisms.     

Core-shell structure in fullerene-containing molecular complexes

A shell model that describes the formation of molecular complexes around a C₆₀ molecule upon the solid-phase interaction of the powders is considered. From the absorption spectra, it follows that a reacting particle is a fullerene dimer.     

Synthesis of bifunctional derivatives of nitroxyl radicals of imidazoline

3-Imidazoline derivatives that contain a substituent with a functional group in the 2 position of the heteroring were obtained by the reaction of 1,2-hydroxyamino ketones with functionally substituted ketones and ammonia. The use of the reactivity of the endocyclic imino group makes it possible to accomplish the synthesis of a number of bifunctional derivatives of nitroxyl radicals of imidazoline and imidazolidine.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 772–778, June, 1990.     

Thermal properties of rare earth dodecaborides

We have measured heat capacity and thermal expansion of rare earth dodecaborides REB₁₂ (RE=Y, Tb-Tm, Lu). YB₁₂ and LuB₁₂ are diamagnetics whereas the other dodecaborides are ordered antiferromagnetically. The amplitude of the heat capacity discontinuity at the Néel temperature and the shape of the heat capacity variation in the critical region for all these antiferromagnetics are characteristics for amplitude-modulated magnetic structures. In the ordered state TbB₁₂ reveals two first-order phase transitions, most likely due to magnetic structure changes. The heat capacity of ErB₁₂ just below the Néel point shows an anomaly of unclear origin. From the Schottky contribution to the heat capacity we have determined crystal field parameters. They are completely different than that is estimated from Point Charge Model.     

Multireference spin-adapted variant of density functional theory

A new Kohn-Sham formalism is developed for studying the lowest molecular electronic states of given space and spin symmetry whose densities are represented by weighted sums of several reference configurations. Unlike standard spin-density functional theory, the new formalism uses total spin conserving spin-density operators and spin-invariant density matrices so that the method is fully spin-adapted and solves the so-called spin-symmetry dilemma. The formalism permits the use of an arbitrary set of reference (noninteracting) configurations with any number of open shells. It is shown that the requirement of degeneracy of the total noninteracting energies of the reference configurations (or configuration state functions) is equivalent to the stationary condition of the exact energy relative to the weights of the configurations (or configuration state functions). Consequently, at any molecular geometry, the weights can be determined by minimization of the energy, and, for given reference weights, the Kohn-Sham orbitals can be determined. From this viewpoint, the developed theory can be interpreted as an analog of the multiconfiguration self-consistent field approach within density functional theory.     

Molecular ions of 3,3′-bi(2-R-5,5-dimethyl-4-oxopyrrolinylidene) 1,1′-dioxides

The electrochemical reduction of 3,3′-bi(2-R-5,5-dimethyl-4-oxopyrrolinylidene) 1,1′-dioxides (R = CF₃, Me, Ph, Bu^t), which are cyclic dinitrons with conjugated C=C bond, in acetonitrile is an EE process producing stable radical anions and dianions, whereas the electrochemical oxidation is an EEC (R = Me, Ph) or EE process (R = Bu^t) with formation of radical cations (except for the case of R = CF₃) and dications (R = Bu^t) stable under standard conditions. Radical cations of the dioxides with R = Me, Ph, and Bu^t and radical anions of the whole series of the compounds studied, including R = CF₃, were characterized by ESR spectroscopy combined with electrochemical measurements and quantum-chemical calculations. The electrochemical behavior of the Bu^t-substituted dinitron is unique: the EE processes in the region of negative and positive potentials with formation of the dianion, radical anion, radical cation, and dication stable at T = 298 K were observed for the first time within one cycle of potential sweep in the CV curve measured in MeCN. __________ Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1148–1154, May, 2005.     

Adsorption of metal halides from ethanol solutions by a 3-n-propylpyridiniumsilsesquioxane chloride-coated silica gel surface

3-n-propylpyridiniumsilsesquioxane chloride polymer, abbreviated as SiPy+Cl-, was used to coat a porous silica gel, SiO2, surface to form the chemically modified solid SiO2/SiPy+Cl-. The resulting polymer film was well adhered to the surface and presented an ion exchange capacity of 0.74 mmol g(-1). Metal halides, MClz [M=Fe(III), Cu(II), and Zn(II)], were adsorbed by the modified solid from ethanol solutions as neutral species by forming the surface anionic complexes described by the equation: mSiO2/SiPy+Cl-+ MClz <=> (SiO2/SiPy+)m[MCl(z+m)]m-, where the [MCl(z+m)]m- species adsorbed on the surface are FeCl4-, ZnCl4(2-), and CuCl4(2-). Accurate estimates of the specific sorption capacities and the heterogeneous stability constants of the immobilized metal complexes were determined with the aid of computational procedures.     

Investigation of conjugated dinitrones — derivatives of pyrroline oxide

The molecular structure of three derivatives ofbis(2- R- 5,5- dimethyl- 3- oxo- 1- oxide pyrrolin- 1- ylidene- 3),where R =CH ₃ (@#@5a @#@), C ₆H₅ (@#@5b @#@), C(CH ₃)₃ (@#@5c @#@), and of the complex of 5b with copper(II)hexafluoroacetylacetonate [Cu(hfac) ₂ (@#@5b @#@)] was investigated by X- ray diffraction analysis in the framework of our studies of the possible tautomeric equilibrium conjugated dinitrone ? nitroxide biradical. The pyrroline rings of the molecules under analysis are planar (rms deviations of atoms are no more than 0.041 å), and the interplanar angles are 32.01(5), 42.84(9), and 51.45(7)? for 5a,5b,and 5c,respectively. It is established that the bond lengths of the C(2)- C(3) =C(3a)- C(2a) fragment are equalized to C(2)- C(3) 1.42 and C(3)- C(3a) 1.40 å. The N→O bond lengths of the nitrone group are within 1.250(4)- 1.282(4) å) [in Cu(hfac)₂ (5b)]. The geometrical data obtained do not permit us to make an unambiguous choice between the tautomeric structures. The magnetic susceptibility measurements of the Cu(hfac)₂ solid complex (5b) and the absence of paramagnetism in solid compounds 5 indicate that they are diamagnetic.     

Transformations of conjugated enamines of the imidazolidine 1-oxide series in the Vilsmeier-Haack reaction

In some cases, the reactions of enaminones of the imidazolidine 1-oxide series with the Vilsmeier reagent afford electrophilic substitution products containing the dimethyl-aminomethylene group. In an acidic medium, these products undergo either hydrolytic elimination of the dimethylaminomethylene moiety or hydrolysis of the latter to form the aldehyde group. The reaction of nitroenamine, which is a derivative of imidazolidine 1-oxide, with the Vilsmeier reagent produces furoxane, viz., the nitroxyl biradical. Reduction of the latter affords the dioxime biradical. Dedicated to the memory of Academician N. N. Vorozhtsov on the 100th anniversary of his birth. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1165–1170, June, 2007.