Abstract: In this work, the physicochemical reactions occurring at the surface of bioactive solâgel derived 3D glass scaffolds via a complete PIXE characterization were studied. 3D glass foams in the SiO2âCaO system were prepared by solâgel route. Samples of glass scaffolds were soaked in biological fluids for periods up to 2 days. The surface changes were characterized using particle induced X-ray emission (PIXE) associated to Rutherford backscattering spectroscopy (RBS), which are efficient methods to perform quantitative chemical maps. Elemental maps of major and trace elements at the glass/biological fluids interface were obtained at the micrometer scale for every interaction time. Results revealed interconnected macropores and physicochemical reactions occurring at the surface of pores. The micro-PIXE-RBS characterization of the pores/biological fluids interface shows the glass dissolution and the rapid formation of a Ca rich layer with the presence of phosphorus that came from biological fluids. After 2 days, a calcium phosphate-rich layer containing magnesium is formed at the surface of the glass scaffolds. We demonstrate that quantities of phosphorus provided only by the biological medium have a significant impact on the development and the formation of the phosphocalcic layer.
Abstract: A simple and efficient strategy for the synthesis of nonorganometallic heterometallic clusters from cheap organometallic precursors is reported. This unique synthetic method involves elimination of the cyclopentadienyl ring from Cp2MCl2 (M = Ti, Zr, Hf) as CpH in the presence of Mâ²L2 or Mâ²Lâ²2 (Mâ² = Ca, Sr, Mn; CH3OCH2CH2OH = LH or (CH3)2NCH2CH2OH = Lâ²H) in an alcohol as a source of protons. In the reactions presented, a series of compounds, [Ca4Ti2(μ6-O)(μ3,η2-L)8(η-L)2Cl4] (1), [Sr4Hf2(μ6-O)(μ3,η2-L)8(η-L)2(η-LH)4Cl4] (2), [Ca4Zr2(μ6-O)(μ-Cl)4(μ,η2-L)8Cl2] (3), [Sr4Ti2(μ6-O)(μ3,η2-L)8(η-L)2(η-LH)2Cl4] (4), [Ca4Zr2Cp2(μ4-Cl)(μ-Cl)3(μ3,η2-L)4(μ,η2-L)4Cl2] (5), [CaTiCl2(μ,η2-Lâ²)3(η-Lâ²H)3][Lâ²] (6), [Ca2Ti(μ,η2-Lâ²)6Cl2] (7), [Mn4Ti4(μ-Cl)2(μ3,η2-L)2(μ,η2-L)10Cl6] (8), and [Mn10Zr10(μ4-O)10(μ3-O)4(μ3,η2-L)2(μ,η2-L)16(μ,η-L)4(η-L)2Cl8] (9), were obtained in good yield. All of the complexes were characterized by elemental analysis, IR and NMR spectroscopy, and single-crystal X-ray structural analysis. Complex 8 belongs to a group of magnetic clusters that consists of Mn4 subunits held together by two μ-Cl bridges. Compounds 6 and 7 underwent thermal decomposition, yielding an alternative source for some heterometallic oxides, which were analyzed by X-ray powder diffraction.
Abstract: Well-defined heterobi- and heteropolymetallic alkoxides are valuable precursors for numerous oxide materials with great application potential. Simple and high yield synthetic routes to such compounds are always highly desirable. This Perspective describes one of the methods that utilizes, as starting materials, homoleptic monometallic alkoxides with a free alcoholic moiety coordinated to the metal. The moiety constitutes a convenient anchor for upcoming organometallics.
Abstract: A simple new route to access heterometallic alkoxo precursors for a wide range of materials is reported. This unique synthetic method comprises elimination of the cyclopentadienyl ring from Cp2MCl2 (M = Ti, Zr) as CpH in the presence of Mâ²(OR)2 (Mâ² = Ca, Mn; OR = OCH2CH2OCH3 or OEt) in an alcohol as a source of protons. In one-pot reactions, we have prepared four different compounds with Ti2Ca4(μ6-O), Cp2Zr2Ca4(μ4-Cl), Zr10Mn10(μ3-O)14, and Cp3Ti2(μ-OEt)2 motifs. The compounds were characterized by single-crystal X-ray structural analysis and NMR spectroscopy.
Abstract: Potential single-source molecular precursors [Ba{(µ-ddbfo)2MRx}2] (ddbfoH = 2,3-dihydro-2,2-dimethylbenzofuran-7-ol; M/R/x = Al/Me/2, Al/Et/2, Ga/Me/2, or Zn/Et/1) for mixed metal oxide materials were prepared by the reaction of barium aryloxide [Ba(ddbfo)2(ddbfoH)2]·3ddbfoH with an appropriate organometallic compound in toluene. The precursors were characterized by elemental analysis, IR and NMR spectroscopy, and single-crystal X-ray structural analysis. The Ba/Al2 and Ba/Ga2 complexes undergo thermal decomposition to give mixed metal oxides BaM2O4 (M = Al, at 1300 °C for both Me and Et derivatives; Ga, at 1430 °C). Instead, the Ba/Zn2 complex decomposes to a mixture of BaCO3 and different metal oxides. The chemical composition and surface morphology of heterobimetallic oxides were analyzed by SEM-EDS and X-ray powder diffraction (XRD) that revealed the formation of highly pure oxide materials with micrometer particle sizes.
Abstract: We have shown here for the first time a facile route to the molecular compound [Mn3Ti(μ3-OCH2CH2OCH3)2(μ-OCH2CH2OCH3)3(μ-Cl)Cl2(OiPr)2] with a Mn3Ti motif, where the Ti atom is in the chiral position and the Mn atoms occupy nonchiral sites.
Abstract: Reactions of oligomeric âCa(dbbfo)2â and Ca9(CH3OCH2CH2O)18(CH3OCH2CH2OH)2 with Al(CH3)3 in toluene gave tetranuclear heterobimetallic [Ca(μ-dbbfo){(μ-dbbfo)(μ-CH3)Al(CH3)2}]2 (71%) and polymeric Ca{(μ-CH3OCH2CH2O)(μ-CH3)Al(CH3)2}2 (86%). The latter can be obtained as monomeric THF adduct Ca{(μ-CH3OCH2CH2O)Al(CH3)3}2(THF)2 (78%) when a mixture of solvents is used. The results, including an initial l-lactide polymerization test, are discussed in the context of calcium alkoxo cluster degradation in solution.
Abstract: The study outlines our initial results that contribute to a better understanding of MAO/MgCl2 (MAO = methylaluminoxane) incorporation in the Cp2ZrCl2/MAO/MgCl2 catalytic system, which is currently of global industrial use. We show here that the[Al3(μ3-O)(Me)5]2+ moiety can be trapped by the tetrapodal [Mg3Cl4(thffo)4(THF)]2- macrounit to form a cluster [Al3Mg3(μ3-O)(thffo)4(Me)5Cl4(THF)] (thffo = 2-tetrahydrofurfuroxide). From this perspective, this macrounit might be considered as a part of the MgCl2 support surface, which fulfills the requirement of a Al3(μ3-O) core.
Abstract: For the last two decades, there has been a growing interest in the development of the chemistry of mixed-metal bi and polynuclear oxo, alkoxo and alkoxo-organometallic complexes. Such interest derives from their fascinating structural chemistry, interesting catalytic properties, and high potential for industrial applications. The fact that most of the heterometallic alkoxo species can generate bimetallic or multimetallic oxides has resulted in high research activity in the field.
In this PhD thesis, entitled âAlkoxo metal complexes as precursors for new oxide materialsâ, are reported syntheses, structures and thermal decompositions of new mono- and mixed metal âsingle-sourceâ precursors (SSP) for oxide materials: [M(ddbfo)2(ddbfoH)2]·3ddbfoH (M = Ba (1), Sr (2); ddbfoH = 2,3-dihydro-2,2-dimethyl-benzofuran-7-ol), [Ba6(iPrO)2(μ3-OiPr)8(μ6-O)(iPrOH)4] (3), [M{(μ-ddbfo)2MâRx}2] (M/Mâ/R/x = Ba/Al/Me/2 (4), Ba/Al/Et/2 (5), Ba/Ga/Me/2 (6), Ba/In/Me/2 (7), Ba/Zn/Et/1 (9), Sr/Al/Me/2 (10)), [Me2M(μ-ddbfo)]2 (M = In (8), Al (11)), [Ca(μ-ddbfo){(μ-ddbfo)(μ-Me)AlMe2}]2 (12), [Ca{(μ-OCH2CH2OCH3)(μ-Me)AlMe2}2] (13), and [Ca{(μ-OCH2CH2OCH3)AlMe3}2(THF)2] (14). The precursors were characterized by elemental analysis (AAS, ICP), IR and NMR (1H, 13C, 27Al) spectroscopy, GC-MS, TG-DTA, and single-crystal X-ray structural analysis.
âSingle-sourceâ compounds can generate ceramic materials in a single step. Such materials deliver appropriate elements of a final product eliminating the need to match the reaction rates required from a multicomponent precursor mixture. Extremely important in this technique is the fact that desired stoichiometry is achieved on the molecular level. This is due to the selective formation of appropriate compound, which can be subsequently thermolyzed to yield the targeted highly pure oxide product. The presented method is an alternative to conventional techniques and the Pechini process and comprises SSP-I/SSP-II precursors.
The chemical composition, surface morphology and measurements of surface-area and pore size of appropriate oxides were analyzed by SEM-EDS, X-ray powder diffraction (powder XRD), and gas-adsorption techniques that revealed the formation of highly pure oxide materials with μm particle sizes.
