T.A. Antonenko

Complexes of organotin compounds with bis- and trisphosphonate derivatives of 2,6-di-tert-butylphenol having antioxidant activity

Complexes of organotin compounds R2SnCl2 with bisand trisphosphonate derivatives of 2,6-di-tert-butyl-4-methylphenol (ionol) were synthesized. X-ray diffraction studies were carried out for some of them. The redox properties of the synthesized compounds were characterized by cyclic voltammetry. Antioxidant/prooxidant activity of the complexes was studied using a new electrochemical method based on measuring the rate of hydrogen atom transfer to the stable radical 2,2´-diphenyl-1-picrylhydrazyl (DPPH). The data obtained were compared with the results of studying activity of the compounds during lipid peroxidation (LP) in biological samples. A correlation is observed between the results on antioxidant activity obtained by electrochemical DPPH test and using biological samples. Unlike the initial organotin compounds, the synthesized complexes have antioxidant activity, whereas phosphorus-containing phenols exhibit the properties of efficient antioxidants and chelating agents.

Thiocarbamide derivatives of europium, holmium, and erbium iodides: Synthesis and structures

Data on the synthesis, IR spectra, and X-ray diffraction analysis of the thiocarbamide complexes of europium, holmium, and erbium iodides, [Ln(H2O)9]I3 · 2CS(NH2)2 (Ln = Eu (I), Ho(II), Er (III)), are presented. The crystal structures of the complexes contain nonaaqualanthanide cations (the polyhedron shape is a monocapped tetragonal antiprism), outer-sphere thiocarbamide molecules, and uncoordinated iodide ions. The thiocarbamide molecules form hydrogen bonds with the aqua cations and join them into continuous layers or network ensembles. The thiocarbamide molecules are disordered in the crystal structures of complexes II and III.

On the reaction products of lanthanide chlorides with biurete

The synthesis and results of IR spectroscopy and X-ray diffraction analysis of new complexes of biurete NH2CONHCONH2 (BU) with the composition LnCl3 · 2BU · 4H2O, where Ln = La (I), Pr (II), Ho (III), Er (IV), and Lu (V), are presented. Crystals of complexes I–V include complex cations [Ln(H2O)4(BU)2]3+ and uncoordinated chloride ions. The coordination mode of biurete molecules is bidentate through the oxygen atoms, and upon coordination the BU molecules are transformed from the initial trans to cis configuration. Water molecules are also coordinated through the oxygen atom (the shape of the polyhedron of the Ln atoms is a two-capped trigonal prism). The oxygen atoms of both BU molecules and the oxygen atoms of the first and second water molecules form a trigonal prism, whereas the oxygen atoms of the third and fourth water molecules form two caps of the coordination polyhedron. The coordinated BU molecules are joined with the chloride ions and water molecules of the adjacent complex cations by hydrogen bonds. The degree of conversion of trans-BU to cis-BU in the lanthanide series of complexes of this type is discussed.

Synthesis and study of new phenolic antioxidants with nitroaromatic and heterocyclic substituents

New polyfunctional aromatic, nitroaromatic, and heterocyclic compounds linked to the 2,6-di-tert-butylphenol moiety via –NH–, –C(O)NH–, –S–, or–C=N– spacers were synthesized. These structures provide intramolecular charge transfer (ICT) and exhibit antioxidant activity. The structures of the new compounds were established by X-ray diffraction. The novel compounds were evaluated for antioxidant activity using the DPPH assay. The presence of the 2,4,6-trinitrophenyl moiety in combination with the –NH– spacer leads to a considerable increase in the antioxidant activity of 2,6-di-tert-butylphenols. These compounds are also weak lipoxygenase inhibitors. The results of this study provide an opportunity to search for new types of antioxidants with ICT.

Structural features of thiocarbamide derivatives of some lanthanide iodides

Data on the synthesis, IR spectroscopy, and single crystal XRD are presented for thiocarbamide compounds of the composition [Ln(H2O)9]I3·2CS(NH2)2, where Ln = Dy (I) and Yb (II). The structural features of [Ln(H2O)9]I3·2CS(NH2)2 (Ln = Pr, Nd, Eu, Gd, Dy, Ho, Er, and Yb) are discussed. The compounds of thiocarbamide with Pr, Nd, Eu, Gd, and Dy iodides are found to form the first isostructural series characterized by a continuous network structure, while with Ho, Er, and Yb iodides the second isostructural series with a layered type structure is formed.