Synthesis,Structure, and Properties of Co2+ and Ni2+ Complexes with the Product of Condensation of 2-(7-Bromo-2-oxo-5-phenyl-3H-1,4-benzodiazepin-1-yl)acetohydrazide and 1H-Indole-2,3-dione

Russian Journal of General Chemistry - [Co(HydrHIz)] and [Ni(HydrHIz)]?2H2O (М = Co, Ni) complexes have been obtained via the reaction of M(CH3COO)2 with...     

Pressure enhancement of the giant magnetocaloric effect in Tb5Si2Ge2

Effects of temperature and pressure on magnetic, elastic, structural, and thermal properties of Tb5Si2Ge2 have been studied by means of macroscopic (thermal expansion and magnetization) and microscopic (neutron powder diffraction) techniques. We present evidence that the high-temperature second-order ferromagnetic transition can be coupled with the low-temperature first-order structural phase change into a single first-order magnetic-crystallographic transformation at and above a tricritical point in the vicinity of 8.6 kbar. This pressure-induced coupling has a remarkable effect on the magnetocaloric effect, transforming Tb5Si2Ge2 from an ordinary into a giant magnetocaloric effect material.     

Asymptotics of nonlinear processes of a controlled approach

Stability of a terminal system of some class that appears in the projection of a control approach is studied, a mathematical model of which is described by a nonlinear system of ordinary differential equations for which no conditions of the existence theorem for solutions constructed by the Lapunov function are satisfied. We obtain criteria of stability, effectiveness of which is shown in concrete examples. nht]mis|Translated from Dinamicheskie Sistemy, No. 7, pp. 62–71, 1988.     

Synthesis and Characterization of Zn(II) Complexes of 2-(7-Bromo-2-oxo-5-phenyl-2,3-dihydro-1<Emphasis Type="Italic">H</Emphasis>-1,4-benzodiazepin-1-yl)acetohydrazide and Its Condensation Products with Pyruvic Acid and Isatin

The systems ZnCl₂–2-(7-bromo-2-oxo-5-phenyl-2,3-dihydro-1H-1,4-benzodiazepin-1-yl)acetohydrazide (Hydr)–propan-2-ol, ZnCl₂–Hydr–pyruvic acid (HPv), and Zn(CH₃COO)₂–Hydr–isatin(HIz)–propan-2-ol were studied. Optimal synthesis conditions were determined, and the complexes [Zn(Hydr)₂Cl₂], [Zn(HydrHPv)₂Cl₂], and [Zn(HydrIz)₂] were isolated. The complexes were characterized by elemental analysis, thermogravimetry, IR spectroscopy, and mass spectrometry. The electrical conductivities of the complexes were measured. The local environment of the central atom in the coordination entity was determined by X-ray absorption spectroscopy.     

Cobalt(II) and nickel(II) complexes with 1-amino-8-hydroxynaphthalene-2,4-disulfonic acid in condensation reactions with aromatic carbonyl derivatives

The condensation reaction of cobalt(II) and nickel(II) complexes with 1-amino-8-hydroxynaphthalene-2,4-disulfonic acid and aromatic carbonyl compounds (benzoin and 2-hydroxy-1-naphthaldehyde) was carried out. Four new complexes (I–IV) were synthesized. The compounds were identified by elemental analysis, powder X-ray diffraction, thermogravimetry, magnetic susceptibility, IR and diffuse reflection spectroscopy, and EXAFS. The spatial arrangement of the donor centers of the ligands in the coordination units (tetrahedral for I, octahedral for II and III, and square planar for IV) was determined.     

Copper(II) complexes with condensation products of aminonaphthalene and benzoin derivatives

New copper(II) complexes with the products of condensation of benzoin with monopotassium 1-amino-8-hydroxy-2,4-naphthalenedisulfonate and 1,8-diaminonaphthalene (complexes I and II, respectively) have been synthesized. The compounds are identified and characterized by elemental analysis; X-ray powder diffraction; thermogravimetry, and electric conductivity data; magnetic susceptibility measurements; and IR, EPR, diffuse reflectance; EXAFS spectroscopy. The geometry and stability of the stereo isomers of complex I are theoretically studied with the use of the molecular mechanics method and semiempirical quantum-chemical calculations. The compositions of the inner spheres of complexes I and II and their coordination polyhedra—a distorted planar square (I) and a distorted octahedron (II)—are determined using different physicochemical methods.