A. S. Bogomyakov

Zinc and cadmium complexes based on 3,6-di-tert-butyl-o-benzoquinone

Zinc and cadmium bis-o-semuquinolate and catecholate complexes are synthesized by the reduction of 3,6-di-tert-butyl-o-benzoquinone (3,6-Q) with amalgamated metals in a medium of various solvents. The oxidation of the metal catecholate derivatives results in the corresponding mono-o-semiquinone complexes, which undergo symmetrization to form the metal bis-o-semiquinolates. The molecular structures of the complexes (3,6-SQ)2Zn · Py, (3,6-SQ)2Zn · H2O, and (3,6-SQ)2Cd · α,α′-Bipy (3,6-SQ is the radical anion of 3,6-Q) are studied by X-ray diffraction analysis. Magnetochemical studies are carried out for the zinc and cadmium bis-o-semiquinone complexes.

The reactivity of o-amidophenolate indium(III) complexes towards different oxidants

The reactivity of o-amidophenolate indium(III) complexes towards different oxidants was investigated. The oxidation reactions were found to proceed through the stage of paramagnetic o-iminobenzosemiquinonato indium(III) derivative formation. The monoradical intermediates undergo symmetrization. The final products of the oxidation processes are corresponding biradical o-iminobenzosemiquinonato indium(III) complexes. In order to understand the reasons for the symmetrization processes steric factors (G-parameters) were evaluated for all intermediates and final products by a method based on the ligand solid angle approach.

Structure of [Dy(Phen)(C4H8NCS2)3]·3CH2Cl2 solvate. Magnetic properties and photoluminiscence of [Ln(Phen)(C4H8NCS2)3] (Ln = Sm, Eu, Tb, Dy, Tm) complexes

It is found that diffraction patterns of complexes I–V of the composition [Ln(Phen)(C4H8NCS2)3] (Ln = Sm, Eu, Tb, Dy, and Tm respectively) are similar. Single crystals of [Dy(Phen)(C4H8NCS2)3]·3CH2Cl2 (VI) obtained are. According to the X-ray crystallographic data, in the structure of VI the unit cell contains two crystallographically independent molecules of the [Dy(Phen)(C4H8NCS2)3] complex and six CH2Cl2 molecules. The N2S6 coordination polyhedron of the Dy atom is a distorted square antiprism. In the range of 2–300 K the magnetic properties of complexes I–V are studied. It is found that complex III passes to the magnetically ordered state; the spontaneous magnetization at 2 K is 24 600 G·cm3/mol. At 300 K compounds I–IV exhibit photoluminescence in the visible spectral range. It is found that the photoluminescence intensity of complex I is several times higher than the photoluminescence intensity of complexes II–IV.

New high-spin iron complexes based on bis(imino)acenaphthenes (BIAN): synthesis, structure, and magnetic properties

The reactions of iron diiodide with one and two equivalents of the monopotassium salt of 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene (dpp-BIAN) in diethyl ether gave the complexes [(dpp-BIAN)FeI]2 (1) and (dpp-BIAN)2Fe (2), respectively. The bis-ligand complex (tms-BIAN)2Fe (3) was synthesized by the exchange reaction of the monosodium salt of 1,2-bis(trimethylsilylimino)acenaphthene (tms-BIAN) with iron diiodide. The reaction of FeI2 with tms-BIAN affords the chelate complex (tms-BIAN)FeI2 (4), whereas the reaction of FeBr2·2H2O with tms-BIAN is accompanied by elimination of trimethylsilyl groups to form the tris-ligand acenaphthene-1,2-diimine complex [(H2BIAN)3Fe][FeBr3·THF]2 (5) containing two types of iron ions. Compounds 1–5 were characterized by IR spectroscopy and elemental analysis. The molecular structures of 1–5 were determined by single-crystal X-ray diffraction. For high-spin complexes 1–3, the temperature-dependent magnetic susceptibilities were measured in the range of 4–300 K.

Synthesis, structure, electrochemical and magnetic properties of 2,6-bis(5-trifluoromethylpyrazol-3-yl)pyridine and its NiII complexes

Abstract2,6-Bis(5-trifluoromethylpyrazol-3-yl)pyridine (H2L) and its mono-, tri-, and tetranuclear NiII complexes were synthesized for the first time. All the obtained compounds were characterized by single-crystal X-ray diffraction analysis. In the complexes, 2,6-bis(5-trifluoromethylpyrazol-3-yl)pyridine exists in the neutral and dianionic forms and exhibits different coordination modes (κ3-, μ2-κ3:κ1-, and μ3-κ3:κ1:κ1). The electrochemical and magnetic properties of all compounds were studied. The tetranuclear NiII complex with the L2− dianion is reduced in two sequential reversible one-electron steps.

Spirocyclic derivatives of nitronyl nitroxides in the design of heterospin Cu II complexes manifesting spin transitions

A method was developed for the synthesis of a nitronyl nitroxide containing cyclopentane substituents in positions 4 and 5 of the imidazoline ring, viz., 2-(3-pyridyl)-4,5-bis(spiropentyl)-4,5-dihydro-1H-imidazole-3-oxide-1-oxyl (LCP). The reaction of CuII hexafluoroacetylacetonate with LCP affords different products depending on the reaction conditions: mononuclear [Cu(hfac)2(LCP)2], binuclear [Cu(hfac)2LCP]2, tetranuclear {[Cu(hfac)2]4(LCP)2}, or chain polymer {[Cu(hfac)2]3(LCP)2}n. Temperature changes induce structural transformations accompanied by a change in the spin state in exchange clusters in the solid [Cu(hfac)2LCP]2 and {[Cu(hfac)2]4(LCP)2}.

Structure of the complex of hexanuclear manganese pivalate with isonicotinamide

The structure of the [Mn6(O)2(Piv)10L2]∞ compound, where Piv is the pivalate anion and L is isonicotinamide, is investigated. Its solid phase is found to be formed by polymeric layers within which hexanuclear fragments {Mn6(O)2(Piv)10} are bound by bidentate bridging L. The molecules of the solvent (Me2CO or EtOAc) in which the synthesis was performed are incorporated into the inter-layer space of the crystal.

Structure and magnetic properties of heterometallic coordination carboxylate polymers with cobalt and lithium atoms

Reactions between lithium pivalate and cobalt coordination polymers [Co5(OH2)(OH)(Piv)9)L1)4]n (I) and [Co2(OH2)(Piv)4(L2)2]n (II), where Piv—is the pivalate anion, L1 is pyrazine, and L2 is pyrimidine, result in new heterometallic polymers {[Li2Co2(Piv)6(L1)2]2MeCN}n (III), {[Li2Co2(Piv)6(L2)]0.5MeCN}n (IV), and [Li2Co2(Piv)6(L2)2]n (V). The resulting compounds contain tetra-nuclear {Li2Co2(Piv)6} fragments connected by neutral bridging ligands (pyrazine or pyrimidine) into layer structures. Crystal structures III–V are determined, and the magnetic properties of III and IV are studied.

Synthesis and magnetic properties of iron(II) closo-borate complexes with tris(3,5-dimethylpyrazol-1-yl)methane

Methods are developed for preparing iron(II) complexes with tris(3,5-dimethylpyrazol-1-yl)methane {HC(3,5-dmpz)3} and closo-borate(2-) ions, namely [Fe{HC(3,5-dmpz)3}2]B10H10 · H2O (I) and [Fe{HC(3,5-dmpz)3}2]B12H12 · H2O (II). These complexes were characterized by static magnetic susceptibility measurements (2–325 K), electronic spectroscopy (diffuse reflectance spectra), and IR spectroscopy. The complexes have a distorted octahedral geometry of the coordination polyhedron; the coordination core is FeN6. μeff(T) studies show low-temperature incomplete spin crossover in complex I and antiferromagnetic exchange coupling among iron(II) unpaired electrons at temperatures below 90 K in complex II. Complex I shows thermochromism; the color transition upon cooling is white ↔ pink.

Synthesis of nitroxyl radical by direct nucleophilic functionalization of a C-H bond in the azadiene systems

Cyclic dinitrones underwent nucleophilic substitution of the hydrogen atom in the reaction with a paramagnetic carbanion, the lithium derivative of 4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazol-1-oxyl 3-oxide, to give polyfunctional nitronyl nitroxyls.