The interrelation of the structure and catalytic properties of hydrogen-reduced iron-ruthenium systems in the ammonia synthesis reaction is studied by X-ray diffraction (XRD), as well as conversion and absorption Mössbauer spectroscopy (MS). It is found that a sample with a metal content of 50Fe/50Ru (wt

Mg-containing solid solutions based on Y 2 FeTaO 7 and formed by various mechanisms of heterovalent substitution were synthesized and had the following compositions: Y 2 Fe 0.55 Mg 0.3 Ta 1.15 O 7 , Y 2 Fe 0.625 Mg 0.3 Ta 1.075 O 7 , Y 2 Fe 0.7 Mg 0.3 TaO 7 , Y 2 Fe 0.7 Mg 0.2 Ta 1.1 O 7 , Y 2 Fe 0.85 Mg 0.15 TaO 7 , Y 1.85 Mg 0.15 Fe 0.925 Ta 1.075 O 7 , and Y 1.85 Mg 0.15 FeTaO 7 . It was shown that all synthesized solid solutions have a pyrochlore-like layered structure (space group P 3 1 21), in which Fe 3+ ions are distributed over three structural positions. The magnetic properties of these solid solutions are due to the presence of a small ferromagnetic component in a predominantly antiferromagnetic system and characterize a ferrimagnet or a canted antiferromagnet with the Néel transition at the Néel temperature T N above room temperature. According to the data of magnetic measurements, two magnetic phase transitions to the ordered phase occur in all the studied samples. Along with the T N transition, in weak magnetic fields and below T N , there is a second transition, which is most likely due to a spin reorientation of the Morin type. The existence of magnetic ordering at room temperature in one magnetic sublattice or an internal magnetic field ( H in ) was confirmed by Mössbauer spectroscopy.

Методами рентгеновской дифракции, конверсионной и абсорбционной мессбауэровской спектроскопии изучена взаимосвязь структуры и каталитических свойств восстановленных водородом железорутениевых систем в реакции синтеза аммиака. Найдено, что образец с содержанием металлов 50Fe/50Ru (мас.%) проявляет максимальную каталитическую активность в синтезе аммиака. Показано, что в бинарной системе формируются наноразмерные кластеры интерметаллида Fe–Ru с размером ОКР ~ 11 нм.

Mg-containing solid solutions based on Y2FeTaO7 and formed by various mechanisms of heterovalent substitution were synthesized and had the following compositions: Y2Fe0.55Mg0.3Ta1.15O7, Y2Fe0.625Mg0.3Ta1.075O7, Y2Fe0.7Mg0.3TaO7, Y2Fe0.7Mg0.2Ta1.1O7, Y2Fe0.85Mg0.15TaO7, Y1.85Mg0.15Fe0.925Ta1.075O7, and Y1.85Mg0.15FeTaO7. It was shown that all synthesized solid solutions have a pyrochlore-like layered structure (space group P3121), in which Fe3+ ions are distributed over three structural positions. The magnetic properties of these solid solutions are due to the presence of a small ferromagnetic component in a predominantly antiferromagnetic system and characterize a ferrimagnet or a canted antiferromagnet with the Néel transition at the Néel temperature TN above room temperature. According to the data of magnetic measurements, two magnetic phase transitions to the ordered phase occur in all the studied samples. Along with the TN transition, in weak magnetic fields and below TN, there is a second transition, which is most likely due to a spin reorientation of the Morin type. The existence of magnetic ordering at room temperature in one magnetic sublattice or an internal magnetic field (Hin) was confirmed by Mössbauer spectroscopy.

The reaction of Fe(III) and Li(I) pivalates and pyridine (py) in acetonitrile affords a molecular heteronuclear complex [Fe 4 Li 2 (O) 2 (Piv) 10 (py) 2 ]·CH 3 CN ( I ), where Piv is pivalic acid anion, with the structural assembly nontrivial for Fe(III) and alkaline metals. The X-ray diffraction data show that complex I contains the hexanuclear motif {Fe 4 Li 2 O 2 } in which, according to the Mössbauer spectroscopy data, the paramagnetic Fe(III) ions exist in the high-spin state ( S = 5/2) in the symmetric octahedral environment of the O and N atoms.

The interaction of the pivalate complexes of iron(iii), [Fe3O(Piv)6(H2O)3]·HPiv, and cadmium(ii), [Cd(Piv)2], in Et2O resulted in one more type of "ferric wheel" family complex, namely [Fe8(Piv)16{Cd(Piv)2}(μ-OH)8]·Et2O (1). The complex is an octanuclear iron(iii) wheel with a {Cd(Piv)2} moiety asymmetrically incorporated into the ring.

Методами конверсионной, абсорбционной мессбауэровской спектроскопии и рентгеновской дифракции изучены фазовый состав и структура оксидных и восстановленных водородом железо-рутениевых систем. В образцах с содержанием металлов (mass.%) 50Fe-50Ru после прокалки на воздухе при 773 и 973 K формируются наносистемы, содержащие две фазы различной степени дисперсности: alpha-Fe2O3 с примесью Ru и RuO2 с примесью Fe соответственно. Изучены структурные превращения наносистемы, прокаленной при 973 K, при различных условиях восстановления. Показано, что формирование наноструктур зависит от начальной и конечной температур восстановления. Присутствие рутения существенно изменяет кинетику восстановления оксидных систем. Показано, что при повышении температуры восстановления наблюдаются перестройки исходных стехиометрических оксидов в промежуточные оксидные структуры переменного состава с различным типом кристаллической решетки. Завершающим этапом восстановления служит образование кластеров металла или твердых растворов интерметаллидов. Ключевые слова: оксид железа-рутения, восстановленные водородом железо-рутениевые системы, структурные преобразования наносистем, конверсионная (CEMS) и абсорбционная мессбауэровская спектроскопия (МС), рентгеновская дифракция.

The phase composition and structure of oxide and hydrogen-reduced iron–ruthenium systems are studied using conversion and adsorption Mössbauer spectroscopy, as well as X-ray diffraction methods. In samples with metal concentration (mass %) 50Fe–50Ru after calcination in air at 773 and 973 K, nanosystems containing two phases with different degrees of dispersion are formed (α-Fe 2 O 3 with an admixture of Ru and RuO 2 with an admixture of Fe, respectively). Structural transformations of the nanosystem calcinated at 973 K in different reduction conditions are investigated. It is shown that the formation of nanostructures depends on the initial and final reduction temperatures. The presence of ruthenium substantially changes the reduction kinetics of oxide systems. It is shown that upon an increase in the reduction temperature, the rearrangement of initial stoichiometric oxides to intermediate oxide structures with varying compositions and with different crystal lattice types is observed. The terminating stage of reduction is the formation of metal clusters or solid solutions of intermetallides.

The phase composition and structure of oxide and hydrogen-reduced iron–ruthenium systems are studied using conversion and adsorption Mössbauer spectroscopy, as well as X-ray diffraction methods. In samples with metal concentration (mass %) 50Fe–50Ru after calcination in air at 773 and 973 K, nanosystems containing two phases with different degrees of dispersion are formed (α-Fe2O3 with an admixture of Ru and RuO2 with an admixture of Fe, respectively). Structural transformations of the nanosystem calcinated at 973 K in different reduction conditions are investigated. It is shown that the formation of nanostructures depends on the initial and final reduction temperatures. The presence of ruthenium substantially changes the reduction kinetics of oxide systems. It is shown that upon an increase in the reduction temperature, the rearrangement of initial stoichiometric oxides to intermediate oxide structures with varying compositions and with different crystal lattice types is observed. The terminating stage of reduction is the formation of metal clusters or solid solutions of intermetallides.

Fe–TiO2 nanoparticles with Fe concentration from 0.24 to 5 wt % were synthesized in a Al2O3 matrix through multiple impregnations from organic solutions of Ti n-butoxide and Fe acetylacetonate. Microstructure, morphology and magnetic properties of the composites were studied using X-ray analysis, transmission electron microscopy, energy-dispersive analysis, Mössbauer spectroscopy and magnetic susceptibility. It was shown that the deposition of the solution with low concentration of Ti n-butoxide leads to the formation of mostly extensive Fe–TiO2 films with a small fraction of individual Fe–TiO2 nanoparticles. On the contrary, the increase of Ti n-butoxide concentration results in the formation of a great number of individual Fe–TiO2 nanoparticles on Al2O3. The size of these particles increases from 2–3 nm to 5–8 nm with the increase of Fe content in the samples from 0.24 to 1.0 (wt %). Mössbauer spectroscopy revealed two types of magnetic ions. The first type of paramagnetic Fe3+ demonstrate spin–lattice relaxation properties while another one substitutes Ti4+ in the TiO2 structure thus forming Fe–TiO2 stabilized particles in the matrix. According to the magnetic data antiferromagnetic and ferromagnetic types of exchange spin coupling occur in Fe–TiO2/Al2O3 composites. The increase of Fe concentration in the composites from 1 to 5 wt % results in the narrowing of the TiO2 band gap from 3.2 to 2.7 eV and shifting the absorption edge in visual spectrum from 350–400 to 450–500 nm.

Fe–TiO2 nanoparticles with Fe concentration from 0.24 to 5 wt % were synthesized in a Al2O3 matrix through multiple impregnations from organic solutions of Ti n-butoxide and Fe acetylacetonate. Microstructure, morphology and magnetic properties of the composites were studied using X-ray analysis, transmission electron microscopy, energy-dispersive analysis, Mössbauer spectroscopy and magnetic susceptibility. It was shown that the deposition of the solution with low concentration of Ti n-butoxide leads to the formation of mostly extensive Fe–TiO2 films with a small fraction of individual Fe–TiO2 nanoparticles. On the contrary, the increase of Ti n-butoxide concentration results in the formation of a great number of individual Fe–TiO2 nanoparticles on Al2O3. The size of these particles increases from 2–3 nm to 5–8 nm with the increase of Fe content in the samples from 0.24 to 1.0 (wt %). Mössbauer spectroscopy revealed two types of magnetic ions. The first type of paramagnetic Fe3+ demonstrate spin–lattice relaxation properties while another one substitutes Ti4+ in the TiO2 structure thus forming Fe–TiO2 stabilized particles in the matrix. According to the magnetic data antiferromagnetic and ferromagnetic types of exchange spin coupling occur in Fe–TiO2/Al2O3 composites. The increase of Fe concentration in the composites from 1 to 5 wt % results in the narrowing of the TiO2 band gap from 3.2 to 2.7 eV and shifting the absorption edge in visual spectrum from 350–400 to 450–500 nm.

The heteronuclear complex [Fe4Li2(O)2(Piv)10(H2O)2] (1, Piv is the pivalic acid anion) was obtained by refluxing FeIII pivalates with LiI pivalates in toluene and isolated as the 1•PhCH3 solvate with a toluene molecule. According to X-ray diffraction data, complex 1 contains the {Fe4Li2O2} core. The Mössbauer spectroscopy data indicate that the core comprises para magnetic FeIII ions in the high-spin state located in the symmetric octahedral environment of oxygen atoms. Thermolysis of 1 studied by simultaneous thermal analysis demonstrated thermal stability of the complex up to 225 °С. The main end product of thermolysis at 600 °С is the mixed oxide LiFe5O8.

Coordination polymers [Fe2MO(Piv)6(L1) x ] n · nSolv (L1 = 1,2-bis(4-pyridyl)ethane, M = Ni (I), Co (II), x = 1.5; M = Cо (III), x = 2) are synthesized. Depending on the synthesis conditions, compounds II (cross diffusion of reactants) or III (fast mixing of reactant solutions) of different compositions are formed. It is shown by X-ray diffraction analysis (CIF files CCDC 1550804 (I) and 1550805 (III)) that compound I is a porous coordination polymer built of parallel 2D layers and compound III is a 1D coordination polymer. The crystals of complexes I and II are isostructural. The mutual arrangement of the 2D layers in compound II depends on the solvent in which this coordination polymer is formed. The desolvation of polymers I and II leads to the collapse of the crystal lattice. Unlike the complexes with L1, [Fe2NiO(Piv)6(L2)1.5] n · nSolv (IV · nSolv) is formed in the case of 4,4'-bipyridine (L2), regardless of the solvent nature, and its crystal lattice is formed by interpenetrating 2D layers. The mutual arrangement of the 2D layers in the crystal lattice of compound IV varies with the solvent used for the synthesis of this coordination polymer or for the resolvation of a sample of polymer IV. It is found that the parameters of the 57Fe Mössbauer spectra for compounds IV and IV · nDEF (DEF is N,N-diethylformamide) differ, which can be explained by a decrease in the symmetry of the coordination environment of the Fe3+ ions when the pores are filled with DEF molecules.

New hexanuclear Fe(III)–Mn(II, III) pivalates [Fe2 III Mn4 II(O)2(Piv)10(HPiv)4] (I) or [Fe4 III Mn2 III(O)2(Piv)12(CH2O2)(HPiv)2] · Et2O (II) are synthesized using the solid-state thermolysis of [Fe2Mn(O)(Piv)6(HPiv)3] (90°С). Complexes I and II differ by the ratio of iron and manganese ions, which depends on the atmospheric composition during thermolysis. The structures of compounds I and II are determined by X-ray diffraction studies. According to the parameters of the Mössbauer spectrum, complex I contains the Fe3+ ions in the high-spin state in the octahedral environment of oxygen atoms.

The possibility of increasing the effectiveness of antitumor drugs such as doxorubicin by preparing its complex with ultrafine magnetic iron oxide nanoparticles is considered. A method for binding doxorubicin molecules to magnetic nanoparticles via citric acid is proposed. The main magnetic properties of the obtained conjugates were studied by proton relaxometry and Mössbauer spectroscopy, while their cytotoxic activity was evaluated via spectrophotometric MTT assay in HeLa cells. It was shown that the conjugates of magnetite nanoparticles with doxorubicin are characterized by a high level of contrast in magnetic resonance imaging. The magnetic properties of doxorubicin-free and bound magnetite nanoparticles are mainly determined by the average size of nanoobjects and the phase composition and slightly depend on the composition of the stabilizing shell. The cytotoxic effect of the synthesized conjugates of magnetite nanoparticles with doxorubicin is higher than that of unbound doxorubicin. This makes it possible to increase the antitumor effect of doxorubicin and control the dynamics of its delivery in the form of a conjugate into the disease focus due to the magnetic contrast properties of nanoparticles.

The multi-layered 3-8 nm ZrO2 particles doped with Fe-57(3+) ions were synthesized by successive impregnations of Al2O3 with a solution of Zr isopropoxide and Fe-57 acetylacetonate. This gave (Fe-ZrO2)/Al2O3 samples containing ZrO2 (approximate to 30 mass%) and different Fe content (0.06-0.26 mass%). By means of XRD, TEM and EDS techniques, it was found that the size of ZrO2 nanoparticles in the (Fe-ZrO2)/Al2O3 samples increases in proportion to the Fe content. According to magnetic measurements and Mossbauer spectroscopy data, (Fe-ZrO2)/Al2O3 samples contain two types of paramagnetic high-spin Fe-57(3+) ions. The Fe-57(3+) ions of type (I) are most probably adsorbed on the outer surface of ZrO2 nanoparticles and are responsible for the spin-lattice relaxation observed in the (Fe-ZrO2)/Al2O3 samples. The Fe-57(3+) ions of type (II) are embedded in the bulk of ZrO2 nanoparticles by replacing the octahedral Zr4+ positions to give a mixed oxide. As the Fe content in the (Fe-ZrO2)/Al2O3 samples increases, the fraction Fe-57(3+) ions of type (I) decreases, while that of Fe-57(3+) ions of type (II) increases. (C) 2016 Elsevier B.V. All rights reserved.

Metal-carrying polysaccharides based on chitosan and a collagen-chitosan composite (collachit) were obtained by modifying polymers by Au and Fe nanoparticles, which were prepared via metal vapor synthesis. Gold nanoparticles were synthesized using organosols with triethylamine; Fe nanoparticles, using the thermally labile bis(arene) complex, viz ., bis(toluene)iron. The composition and structures of the resulting materials were studied by Mössbauer spectroscopy, XPS, and X-ray diagnostics using synchrotron radiation. Particles of Au (7.5–10 nm) and Fe (6–7 nm) were detected in metallopolymers by X-ray powder diffraction. The XPS analysis of gold-containing nanocomposites showed two states of Au4f. One of them is metallic with the binding energy of the Au4f 7/2 peak equal to 83.8 eV, and another one is partially oxidized with the binding energy of the Au4f 7/2 peak equal to 85.5 eV; the atomic concentrations of the two states are 16% and 84%, respectively. A comparative analysis of the Mössbauer spectra of iron-containing chitosan and collachit demonstrated that these two samples have similar structures. Thus, iron is present as a metallic phase (−30%) and a superparamagnetic gamma-iron oxide (−74%). The size of gamma-iron oxide nanoclusters in the samples can be estimated at −6–8 nm.

A new iron(iii) coordination compound with the benzene-1,3,5-tricarboxylate anion of the composition [Fe iii 2(OH)0.3(H2O)1.7(btc)4/3]Cl1.7·2.8DMF·1.9H2O (1) was synthesized. Its crystal structure was determined, and the Mössbauer spectra were analyzed. The adsorption of salicylaldehyde and nitromethane by compound 1 was studied. The adsorption kinetics of salicylaldehyde is described by the pseudo-second order equation. The diffusion of this aldehyde in particles of compound 1 is, most probably, the rate-limiting step in the Henry reaction.