I. S. Vasil’chenko

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.

Molecular design of azomethine complexes

Data on the coordination chemistry of azomethines, which are based on the molecular design concept formulated and developed by V.I. Minkin and his disciples, are generalized and systematized. Particular attention is given to the methods for targeted synthesis of five- and/or six-membered chelates containing chalcogen atoms (S, Se, and Te) and nonstandard (heteroleptic, molecular, and supramolecular) structures. Achievements in the design of magnetically active and luminescent complexes and azomethine complex additives to lubricants are discussed.

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.

Metal complexes with azomethines containing the isomeric E-Z azo fragments

Cobalt and zinc complexes with phenylazosalicylaldehyde azomethines were obtained by chemical and electrochemical syntheses. The B3LYP/6-311G(d, p) calculations showed that the azo group in both the ligands and the complexes are mainly in the E-form.

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.

Chemical and electrochemical syntheses of the binuclear zinc and cadmium chelates based on the sterically hindered Schiff bases

Chemical and electrochemical syntheses of a series of the zinc(II) and cadmium(II) complexes were carried out on the basis of sterically hindered Schiff bases, which are the condensation products of 4,6-di-tert-butyl-2-aminophenol with the salicylaldehyde derivatives (H2L, H2L1). The structures and compositions of the synthesized binuclear complexes M2L2 and M2L21 where M = Zn(II) and Cd(II), were proved by the data of elemental analysis, IR spectroscopy, and 1H NMR spectroscopy. The structures of the Zn2L2 · 2Py and Zn2L2 · 2DMF dimers were proved by X-ray diffraction analysis. The electrochemical dissolution of zero-valence zinc and cadmium in methanol in the presence of equimolar amounts of H2L and H2L1 made it possible to isolate dimeric complexes of the corresponding metals of the composition M2L2 and M221.

Electrochemical and chemical synthesis and structure of adducts (CH3OH and H2O) of metal chelates of N,N,O tridentate pyrazole-containing Schiff base

Chemical and electrochemical synthesis of a series of cobalt(II), nickel(II), copper(II), and zinc(II) complexes of tridentate Schiff base (H2L), a product of condensation of N-(2-aminophenyl)-4-methylbenzenesulfonamide (2-tosylaminoaniline) with 1-phenyl-3-methyl-4-formylpyrazol-5-ol was accomplished. The structure and composition of metal-chelates were established by the C, H, N elemental analysis, IR, 1H NMR, EXAFS spectroscopy and magnetochemical data. The structures of all complexes were confirmed by of X-ray crystallography.

Binuclear and polynuclear complexes of Schiff bases

The data on the synthesis of binuclear and polynuclear homo- and heterometallic complexes of aromatic and heterocyclic (azole) Schiff bases are summarized and systematized. Influence is revealed of the structure (nature of aldehyde and amine moieties and intermetallic bridges) of azomethine binuclear copper chelates on their magnetic characteristics. The complexes with N,N-or S,S-bridging atoms are shown to lead, in general, to ferromagnetic exchange whereas O,O-intermetal binding leads to antiferromagnetic spin-spin coupling.

Synthesis and Magnetic Properties of New Binuclear Cu(II) Complexes with Tridentate Azomethine Ligands

New binuclear copper complexes of tridentate azomethine ligands with various combinations of N, O, and S donor centers were prepared by various procedures, including template synthesis. The magnetochemical data obtained for the range 2-300 K suggest the occurrence of antiferromagnetic coupling in most of these chelates. The only exception is the complex containing N-tosyl and N-ethyl donor fragments, in which the ferromagnetic exchange is observed.