Synthesis of N,N′-bis[4-(1H-1,2,3-triazol-1-yl)furazan-3-yl]-methylenediamine derivatives

[3+2] Cycloaddition of azide groups of N,N′-bis(4-azidofurazan-3-yl)methylenediamine to 1,3-dicarbonyl compounds and malonodinitrile was shown to proceed regioselectively with the formation of the corresponding N,N′-bis[4-(1H-1,2,3-triazol-1-yl)furazan-3-yl]methylenediamine derivatives. The reactions of N,N′-bis(4-azidofurazan-3-yl)methylenediamine with cyanoacetic acid ethyl ester and amide led to the formation of the product of transformation of the azide group in the starting compound to the amino groups.     

The conduction current in a metal-insulator-metal structure

The flow of the conduction current in a metal-insulator-metal structure under X-ray and optical excitation is considered. Accumulation of positive charge at the negative electrode in the KBr and CsI crystals is studied. The method of discharge currents after the X-ray and optical excitation is suggested for estimation of the near-surface charge. It is shown that the values of charge transported by the conduction current and those determined from the measured discharge-current signal are in satisfactory agreement. The lifetimes of near-surface charges of holes and anionic vacancies and the values of the electric-field strength at the metal-insulator interface are estimated. It is assumed that electroneutrality of the sample is established owing to the motion of electrons from the surface into the bulk over dislocations.     

Thermolysis of furoxans annulated with five-membered carbocycles in the presence of dipolarophiles

The conditions for the thermolysis of furoxans annulated with differently strained five-membered carbocycles (cyclopentafuroxan 1, norbornenofuroxan 2, and acenaphthofuroxan 3) to bis(nitrile oxides) in the presence of various dipolarophiles (diethyl acetylenedicarboxylate, benzoylformonitrile, and ethoxycarbonylformonitrile) were optimized. It was found that the reactivities of the above furoxans as sources of bis(nitrile oxides) decrease in the order 2 > 1 > 3. Among the furoxans studied, only norbornenofuroxan 2 can be recommended as a possible cross-linking reagent for polymers. The formation of di-N-oxides of 3,4-bis(cyanopropyl)-, 3,4-bis(cyanocyclopentyl)-, and 3,4-bis(cyanonaphthyl)furoxans was detected. They resulted from intermolecular cyclodimerization of bis(nitrile oxides) initially formed in the thermolysis of furoxans 1–3. Dedicated to Academician V. A. Tartakovsky on the occasion of his 75th birthday. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1521–1528, August, 2007.     

Electronic structure of transition metals under pressure

Conclusions In this short review we have tried to demonstrate the advances made in the intensive study of the behavior of the electronic structure of metals under pressure in recent years. The alloys of transition metals, including intermetallic ordered compounds, have for the time being proved to lie outside the scope of this review, mainly because of the lack, in practice, of theoretical calculations in this area. Clearly, progress in this field is also being held up by the lack of detailed experimental investigations devoted to the behavior of alloys under pressure. This is due to the complexities involved in carrying out many traditional experimental procedures under high pressures. We should like to emphasize, however, that at the present time theoretical calculations have taken on a predictive power and this gives reason to hope that progress in calculations will in turn stimulate progress in experimentation.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 50–62, December, 1982.     

Thermodynamics and the mechanism of interaction of adenine with amino acids in water

Two groups of amino acids, which react differently with adenine, are distinguished. In the case of nonpolar and aliphatic amino acids, the endothermic effect of dehydration plays a decisive role, while in the case of aromatic, polar, and charged amino acids the exothermic effect of interaction with adenine is dominant. Associates of Ade with Lys. HCl, His, Trp, Asp, and Glu were found. It was demonstrated that the complex-forming ability of purines (Ade and Caf) is higher than that of pyrimidines. Based on the linear enthalpy-entropy compensation effect for complexes of amino acids with adenine, it was suggested that the hydration state of interacting molecules contributes significantly to interactions of Ade with amino acids.     

Radiation-induced conductivity of alkali halide crystals in strong electric fields under X-ray and photoexcitation

A study is undertaken into radiation-induced conductivity of alkali halide crystals under X-ray excitation and sequential excitation with X-ray and laser pulses within the absorption band of F-and F ⁻-centers. The basic conduction parameters (concentration and lifetime of carriers upon X-ray and photoexcitation) are estimated. The possible processes responsible for the nonlinearity of the current-voltage characteristics are discussed. It is shown that an increase in the conductivity in strong electric fields may be due to a decrease in the spatial localization of electrons in the conduction band of the insulator.     

Application of 57Co emission Mössbauer spectroscopy to studying biocomplexes in frozen solutions

Emission Mössbauer spectroscopy with the ⁵⁷Co isotope was used to study very dilute rapidly frozen aqueous solutions of cobalt(II) complexes with low-molecular-weight biomolecules (aromatic amino acids – anthranilic acid and L-tryptophan) and within a sophisticated biopolymer, bacterial glutamine synthetase, a key enzyme of nitrogen metabolism. The appearance of after-effects of the ⁵⁷Co→⁵⁷Fe nuclear transformation as well as the coordination properties of the cation and the ligands in the complexes are discussed on the basis of their Mössbauer parameters.