V. G. Vlasenko

New magnetically active metal complexes of tridentate Schiff bases of phenylazosalicylaldehyde

The bidentate chelate Cu(II) complexes of phenylazosalicylaldehyde azomethines are synthesized for the first time and their magnetic properties are studied. The complexes with the intermetallic bridge of the nitrogen atoms are characterized by the antiferromagnetic interaction, whereas the ferromagnetic exchange is typical of analogous coordination compounds with the sulfur bridge.

Crystal Chemistry of Lead Titanate in Relation to Its Electrical Properties

The origin of the discrepancy between the measured average parameter of the perovskite unit cell of PbTiO3and the unit-cell parameter calculated for an ideal perovskite structure is analyzed with the use of extended x-ray absorption fine structure spectroscopy data, which demonstrate that PbTiO3contains Pb4+ions. The amount of Pb4+depends on the preparation conditions and may attain ≃6 at. %. Assumption is made that the presence of crystallographic shear planes allows a fraction of the Pb2+ions to occupy octahedral sites near the shear planes. The maximum content of Pb2+on the B site is ≃2.5 at. %. The formula proposed for the cation composition of imperfect lead titanate differs from the ideal formula Pb2+Ti4+O3and indicates that lead titanate can be thought of as an internal solid solution. It is shown that the composition of lead titanate influences its electrical properties: ε/ε0increases with Pb4+concentration and exceeds that in single crystals by an order of magnitude.

New ferro-and antiferromagnetic complexes of tridentate azomethines with copper

Tridentate azomethine ligands with N2O4 and N3donor atoms and their copper complexes were synthesized and characterized. The dimeric structure of copper(II) chelates was confirmed by EXAFS studies. Complexes based on 2-tosylaminobenzaldehyde azomethines tend to undergo ferromagnetic exchange, whereas similar salicylaldehyde derivatives have antiferromagnetic exchange.

Iron(III) Oxide Nanoparticles in a Polyethylene Matrix

A method is proposed for the preparation of iron(III) oxide nanoparticles via thermal decomposition of iron(III) acetate in a high-temperature solution of polyethylene. The nanoparticles were characterized by EXAFS, EPR, and Mössbauer spectroscopy. The nearest neighbor environment of Fe in the nanoparticles was shown to be similar to that in the structure of γ-Fe2O3 . According to the Mössbauer results, the material contains iron(III) oxide in superparamagnetic and ferromagnetic states similar to γ-Fe2O3 . The particle size determined by high-resolution transmission electron microscopy is consistent with x-ray diffraction data. Experimental data are presented on the field-dependent magnetization of the material.

Influence of the bridging coordination of DMSO on the exchange interaction character in the binuclear copper(II) complex with the nonsymmetrical exchange fragment

The binuclear copper(II) complex [Cu2L(CH3COO)] (I), where L3− is the azomethine trianion based on 3-methyl-4-formyl-1-phenylpyrazol-5-one and 1,3-diaminopropan-2-ol, and its DMSO adduct (II) in which the DMSO molecule acts as an additional bridging ligand are synthesized. The structure of complex II is determined by X-ray diffraction analysis, and the structure parameters of the coordination unit of complex I are determined by EXAFS spectroscopy. The μ2-coordination of the DMSO molecule in compound II results in a change in the sign of the exchange interaction parameter. In complex I, the antiferromagnetic exchange interaction (2J = −169 cm−1) occurs between the copper(II) ions. The exchange interaction of the ferromagnetic type (2J = 174 cm−1) is observed in complex II. The quantum-chemical calculations of the magnetic exchange parameters by the density functional theory method show that the role of the DMSO molecule as a switch of the exchange interaction character is exclusively the stabilization of the “broken” conformation of the metallocycles.

1-amino-2-thiobenzimidazoleimines as novel ambidentate ligand systems

Azomethine derivatives of 1-amino-2-thiobenzimidazole (H2L) were synthesized and studied by IR and 1H NMR spectroscopy. Thiobenzimidazoline tautomeric form of these compounds was found to predominate in a solid state and DMSO solution. Novel mono-and binuclear metal chelates M(HL)2 and M2L2 (M = Ni(II), Cu(II), Co(II), Zn(II), Cd(II)) were synthesized on the basis of H2L derivatives and their composition and structures were established from IR, 1H NMR, EXAFS, and magnetochemical data. The composition of coordination sphere was shown to produce no effect on ferromagnetic exchange in binuclear Cu(II) complexes.

Molecular Design of New Magnetically Active Copper Complexes with Heteroaromatic Schiff Bases and Azo Compounds

Copper chelates with tridentate ligands containing pyridine or pyrazole ring at the azomethine or azo fragment were synthesized by chemical electrochemical methods, and their structure was characterized by the EXAFS spectra. Thermal magnetochemical analysis of the complexes revealed antiferromagnetic exchange interaction in all complexes. The exchange interaction parameter of the complex containing an N-tosylamino group in the ortho position with respect to the azomethine group is much lesser than that of the corresponding complex having an oxygen atom in the same position. The copper chelate derived from azopyrazole ligand shows low-temperature ferromagnetic phase transition.

Synthesis and structures of nickel(ii) complexes with thioether-containing β-aminovinyl ketones

New ligands, viz., thioether-containing β-aminovinyl ketones, and NiII complexes with these ligands were synthesized. The compounds were characterized by X-ray diffraction analysis, EXAFS, NMR, and IR spectroscopy, and magnetochemistry.

Copper Nanoparticles in a Polyethylene Matrix

The composition and structure of Cu-containing nanoparticles stabilized in a polyethylene matrix were studied. The nearest neighbor environment of Cu in the 15-nm particles is similar to that in metallic Cu. In contrast to Fe nanoparticles, the Cu nanoparticles embedded in polyethylene do not oxidize during storage in air.

Synthesis, structure, photo- and electroluminescence studies of bis[2-(N-tosylamino)benzylidene-4′-dimethylaminophenylaminato]zinc

A new bis[2-(N-tosylamino)benzylidene-4′-dimethylaminophenylaminato]zinc complex was synthesized, its structure was studied by methods of elemental analysis, IR spectroscopy, 1H NMR spectroscopy, X-ray absorption spectroscopy, and quantum chemical calculations. Electron absorption and photoluminescence spectra of the zinc complex were investigated. An OLED device based on it was made and found to emit “soft” yellow light with CIE coordinates (x = 0.431, y = 0.537) and radiation luminance 1300 cd m−2 at a working voltage of 14 V.