Ligand effects on the ferro- to antiferromagnetic exchange ratio in bis(o-semiquinonato)copper(II)

Heterospin complexes [Cu(SQ)2Py].C7H8, Cu(SQ)2DABCO, and [Cu(SQ)2NIT-mPy].C6H6, where Cu(SQ)2 is bis(3,6-di-tert-butyl-o-benzosemiquinonato)copper(II), DABCO is 1,4-diazabicyclo(2,2,2)octane, and NIT-mPy is the nitronyl nitroxide 2-(pyridin-3-yl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-3-oxide-1-oxyl, have been synthesized. The molecules of these complexes have a specific combination of the intramolecular ferro- and antiferromagnetic exchange interactions between the odd electrons of Cu(II) and SQ ligands, characterized by large exchange coupling parameters |J| approximately 100-300 cm(-1). X-ray and magnetochemical studies of a series of mixed-ligand compounds revealed that an extra ligand (Py, NIT-mPy, or DABCO) coordinated to the metal atom produces a dramatic effect on the magnetic properties of the complex, changing the multiplicity of the ground state. Quantum chemical analysis of magnetostructural correlations showed that the energy of the antiferromagnetic exchange interaction between the odd electrons of the SQ ligands in the Cu(SQ)2 bischelate is extremely sensitive to both the nature of the extra ligand and structural distortions of the coordination unit, arising from extra ligand coordination.     

Influence of deviation from stoichiometry on the plasticity and mechanism of fracture of the boron-alloyed intermetallic compound Ni3Al obtained by self-propagating high-temperature synthesis

We have studied the effect that deviation of the composition of an ally from stoichiometry has on the plasticity , strength _B, and the fracture mechanism of the intermetallic compound Ni₃Al obtained by self-propagating high-temperature synthesis. The variation of the tensile strength, plasticity, type of fracture, and the cohesive strength _coh of grains have been show to be correlated. The cohesive strength increases with the Al content in the alloy, most rapidly up to 24.0 at. % Al.V. D. Kuznetsov Siberian Physicotechnical Institute, Tomsk State University. Institute of Strength Physics and Materials Science, Siberian Branch, Russian Academy of Sciences. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 104–110, April, 1994.     

Mass spectrometric identification of ring-chain tautomers of 4-cyano-3-pyrazolidones in the gas phase

Analysis of the electron impact mass spectra of a series of 4-cyano-3-pyrazolidones, which manifest ring-chain tautomerism in polar solvents, showed that these compounds also exist in the gas phase as a mixture of tautomers, which undergo characteristic fragmentation. The quantitative tautomer ratio in this series is a function of electronic and steric substituent effects. The fragmentation pathways for each of the tautomers were determined using high-resolution mass spectrometry.M. V. Lomonosov Moscow State University, 119899 Moscow. Yerevan State University, 375025 Yerevan. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp 1525–1530, November, 1995 Original article submitted November 1, 1995.     

Microscopic and mesoscopic structure of pressure-synthesized intermetallic Ni3Al

Optical metallography and transmission diffraction electron microscopy are used to show that the micro- and mesostructure of cast and pressure-synthesized intermetallic Ni₃Al differ considerably. Four types of grains of the major Ni₃Al phase are revealed in the synthesized intermetallide that differ in their domain and dislocation structure. These are single- and polydomain grains with or without dislocations. Institute of Strength Physics and Materials Science, Siberian Branch of the Russian Academy of Sciences. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 53–56, July, 1999.     

Synthesis, structure, and properties of a new representative of the family of calix[4]arene-containing [MnII 2MnIII 2]-clusters

A new representative of calix[4]arene-containing tetranuclear manganese complexes of the [Mn^II ₂Mn^III ₂] type was obtained. According to the data of magnetoochemical studies, the complex exhibits properties of molecular magnet at the temperature below 5 K. Parameters of the exchange interaction and the activation energy were determined. The influence of the peripheral environment on the magnetic properties of the tetranuclear manganese framework in the structure of the complex was revealed.     

5-Phenyl-1,3,4-thiadiazole and 5-phenyl-1,2,4-triazoline-3-thione as products of dehydrogenation of cyclic tautomeric forms of benzaldehyde thiosemicarbazone

5-Pkenyl-1,3,4-thiadiazole and 5-phenyl-1,4-triazoline-3-thione are produced from heterocyclic tautomeric forms of benzaldehyde thiosemicarbazone in the gas phase under conditions existing in a mass spectrometer, and also in the solid phase in the course of thermolysis.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1554–1560, November, 1993.