The mutual influence of ligands in transition metal bis-chelates

Electronic structure quantum chemical calculations of the Fe(II), Ni(II) and Cu(II) bis-chelate series are reported. The nature of the ligand mutual influence effect on these compounds is elucidated. This effect manifests itself in polarization of metal—ligand bonds. The ligands which have highly covalent bonds with the metal form bonds of even greater covalent character in mixed complexes, whereas bonds for the other ligands become more ionic.     

Analytical Application of Silica Gel Modified with Didecylaminoethyl-beta-Tridecylammonium Iodide

Sorption of a high molecular weight quaternary ammonium salt, didecylaminoethyl-β-tridecylammonium iodide (DDATD) on different types of sorbents was investigated. The nature of reagent adsorption on silica gel was examined by spectroscopic and computer methods. The sorption of anionic metal complexes of cobalt, copper, zinc and manganese on silica gel modified with DDATD was studied. The possibility of recovery of cobalt and copper thiocyanate complexes and their further atomic absorption determination is shown. Modified sorbent was applied to cobalt chemiluminescence and determined in natural water and a nickel preparation (detection limit, 2 μg/l.).     

Effect of hydrogenation on spin-reorientation phase transitions and magnetic anisotropy constants of RFe11Ti single crystals (R=Lu, Ho, and Er)

The magnetic anisotropy and spin-reorientation phase transitions in single crystals of the RFe₁₁Ti (R=Lu, Ho, and Er) compounds and their hydrides are investigated. Measurements are carried out on capacitance and torque magnetometers. The magnetic anisotropy constants K ₁ and K ₂ are determined by the mathematical processing of experimental magnetization curves in terms of the phenomenological theory of the anisotropic ferromagnet magnetization. It is demonstrated that the hydrogenation strongly affects the magnitude and the sign of magnetic anisotropy constants, as well as the spin-reorientation phase transitions. The hydrogenation of the HoFe₁₁Ti compound leads to the change in sign of the magnetic anisotropy constant K ₁. The inference is made that a change in the atomic volume and the axial ratio c/a cannot result in the observed effects. A change in the magnetic anisotropy constants upon hydrogenation is primarily due to the change in the interaction of the quadrupole moment of a 4f electron subshell of rare-earth ions with surrounding ions of the crystal lattice and also with valence and conduction electrons.     

Zinc(II) Complexes with Azomethines of 2,4,6-Trimethylaniline and Halogen-Substituted Salicylaldehyde

Russian Journal of General Chemistry - Azomethines were synthesized from 2,4,6-trimethylaniline, salicylaldehyde, and its 3(5)-halogen derivatives, as well as their complexes with zinc(II) (ZnL2)....     

Base-free aerobic oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid over Pt/C catalysts synthesized by pulse alternating current technique

The Pt/C catalysts with various Pt content (5-30 wt%) synthesized via electrochemical pulse alternating current technique have been evaluated for the base-free aerobic oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid. The higher Pt content in the catalyst (30 wt%) provides the product yield up to 65% upon performing the process in concentrated (～0.1 M) aqueous solutions of the substrate.     

Synthesis of functionally substituted isoxazole and isothiazole derivatives

Acylation of benzene and toluene with 5-phenyl- and 5-(p-tolyl)isoxazole-3-carbonyl chlorides gave 5-phenyl(or p-tolyl)isoxazol-3-yl phenyl(or p-tolyl)ketones which were reduced to the corresponding alcohols with sodium tetrahydridoborate in propan-2-ol. Selective reduction of the carboxy group in 4,5-dichloroisothiazole-3-carboxylic acid was achieved by the action of BH₃, and the aldehyde group in 4-formyl-2-methoxyphenyl 5-arylisoxazole-3-carboxylates and 4,5-dichloroisothiazole-3-carboxylates was reduced to hydroxymethyl group with sodium triacetoxyhydridoborate in benzene. Acylation of the resulting hydroxymethyl derivatives with 5-arylisoxazole- and 4,5-dichloroisothiazole-3-carbonyl chlorides afforded the corresponding esters containing two azole fragments in their molecules.     

Esters of isoxazole- and isothiazolecarboxylic acids and oximes of β-isatin, isoxazole- and ferrocene-containing ketones and carborane alcohols

Oximes of β-isatin, isoxazole- and ferrocene-containing ketones, o- and m-carborane alcohols react with isoxazol- and isothiazolecarboxylic acid chlorides in the presence of triethylamine to afford the corresponding esters.     

Physicochemical study of binuclear copper(II), oxovanadium(IV), and iron(III) complexes with bis-1′-phthalazinylhydrazone of 2,6-diformyl-4-tert-butylphenol

Binuclear copper(II), oxovanadium(IV), and iron(III) complexes with bis-1′-phthalazinylhydrazone of 2,6-diformyl-4-tert-butylphenol have been prepared. An antiferromegnetic exchange interaction between the paramagnetic centers was found. Redox properties of the complexes were studied by the methods of cyclic and differential pulse voltammetry; the reduction of Cu(II) complexes was shown to proceed in two consecutive one-electron steps.     

Synthesis of 4,5-dichloro-3-cyanoisothiazole and its functional derivatives

By treating with phosphorus pentoxide the 4,5-dichloroisothiazole-3-carboxamide 4,5-dichloro-3-cyanoisothiazole was synthesized whose reactions with piperidine, phenyl-and benzylthiols occurred with replacement of the chlorine atom in the position 5 by the residue of the corresponding nucleophile. Reactions with sodium thiobytylate and also with sodium methylate in methanol led to the formation both of the products of chlorine substitution by BuS or MeO groups respectively and of addition products of methanol to the cyano group. The reaction of butanethiol with cyanoisothiazole in 2-propanol in the presence of sodium 2-propylate was more selective and resulted in the replacement of the chlorine atom in the position 5 by the residue of the butanethiol.