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5,10,15,20-Tetrakis(4-sulfonatophenyl)porphyrin was entrapped into biocompatible hydrogels formed by self-assembling micelles of the titanium dioxide prepared by hydrolysis of titanium ethoxide modified with triethanolamine (TEA). The materials were characterized by their optical and photosensitive properties. The immobilization led to changes of the absorption spectra of the dye and decreased its molar absorption coefficient. The TiO2 matrix did not degrade the entrapped porphyrin upon u.v. irradiation. The formation of TEA–titanium(IV) chelates facilitated a controlled and triggered release of the immobilized dye from the hydrogels in lactate and citrate buffers. The released dye prolonged the sterility of citrate–phosphate buffer and its illumination with visible light inhibited growth of Aspergillus niger.

Strontium titanate SrTiO3 thin films are highly perspective as gate dielectric material. Difference in volatility of the common homometallic precursors-strontium beta-diketonates and titanium alkoxides remains major hinder for preparation of high quality coatings based on this phase. An attractive alternative in its synthesis by MOCVD is provided by application of heterometallic mixed-ligand complexes, Sr2Ti2(beta-diket)4(OR)8(ROH)x. Mass-spectrometric study reveals, however, that none of these species can be considered a true single-source precursor. The relative stability of the molecules in solution and the congruence of in-situ release of homometallic species on evaporation are, on the other hand, crucial for the quality of the produced films and are strongly influenced by the nature of alkoxide ligands, OR. The historically first discovered representative of this heterometallic family, a sec-alkoxide derivative Sr2Ti2(thd)4(O(i)Pr)8, is in fact unexpectedly unstable, transforming in solution into Sr2Ti(thd)4(O(i)Pr)4((i)PrOH), which explains difficulties in keeping the correct stoichiometry using isopropoxide precursor. The primary alkoxide complexes, Sr2Ti2(thd)4(OR)8(ROH)2, R = Et, (n)Pr are also unstable yielding Sr4Ti2(thd)4(OR)8(ROH)2 on decomposition. The best solution stability and most uniform evaporation was observed for the iso-derivative, Sr2Ti2(thd)4(O(i)Bu)8, permitting to apply it in long term experiments under industrial process conditions. Present contribution provides detailed experimental comparison between and sec-and iso-alkoxide derivatives and sheds light on the influence of the ligand on molecular stability of a precursor and how it influences the quality of the derived oxide film, especially in relation to its electrophysical properties.

Transmission Electron Microscopy (TEM) on light element materials and soft matters is problematic due to electron irradiation damage and low contrast. In this doctoral thesis techniques were developed to address some of those issues and successfully characterize these materials at high resolution. These techniques were demonstrated on graphene flakes, DNA/magnetic beads and a number of water containing biomaterials. The details of these studies are given below.A TEM based method was presented for thickness characterization of graphene flakes. For the thickness characterization, the dynamical theory of electron diffraction is used to obtain an analytical expression for the intensity of the transmitted electron beam as a function of thickness. From JEMS simulations (experiments) the absorption constant λ in a low symmetry orientation was found to be ~ 208 nm (225 ± 9 nm). When compared to standard techniques for thickness determination of graphene/graphite, the method has the advantage of being relatively simple, fast and requiring only the acquisition of bright-field (BF) images. Using the proposed method, it is possible to measure the thickness change due to one monolayer of graphene if the flake has uniform thickness over a larger area.A real-space TEM study on magnetic bead-DNA coil interaction was conducted and a statistical analysis of the number of beads attached to the DNA-coils was performed. The average number of beads per DNA coil was calculated around 6 and slightly above 2 for samples with 40 nm and 130 nm beads, respectively. These results are in good agreement with magnetic measurements. In addition, the TEM analysis supported an earlier hypothesis that 40 nm beads are preferably attached interior of the DNA-coils while 130 nm beads closer to the exterior of the coils.A focused ion-beam in-situ lift-out technique for hydrated biological specimens was developed for cryo-TEM. The technique was demonstrated on frozen Aspergillus niger spores which were frozen with liquid nitrogen to preserve their cellular structures. A thin lamella was prepared, lifted out and welded to a TEM grid. Once the lamella was thinned to electron transparency, the grid was cryogenically transferred to the TEM using a cryo-transfer bath. The structure of the cells was revealed by BF imaging. Also, a series of energy filtered images was acquired and C, N and Mn elemental maps were produced. Furthermore, 3 A lattice fringes of the underlying Al support were successfully resolved by high resolution imaging, confirming that the technique has the potential to extract structural information down to the atomic scale. The experimental protocol is ready now to be employed on a large variety of samples e.g. soft/hard matter interfaces.

Application of different solvating ligands drastically changes the composition and geometry of bimetallic sodium−tantalum pinacolates, forming insoluble and stable organic−inorganic hybrid material...

The first representatives of alkoxy-zircono-silsesquioxane compounds, dinuclear [Cy7Si7O12]Zr(ROH)(μ-OR)2Zr(ROH)[O12Si7Cy7], where R = nPr, nBu, tBu; Cy = c-C6H11, and [Cy*7Si7O12]Zr(μ-ROH)(μ-OR)2Zr[O12Si7Cy*7], R = tBu; Cy* = c-C5H9, have been prepared with quantitative yield by interaction of the corresponding zirconium alkoxides with the cycloalkyl-substituted cage silsesquioxanes in hexane. The X-ray single crystal study of the n-butoxide derivative revealed that zirconium atoms are hexacoordinated with the 3 oxygen atoms of the cage ligand, 2 — from the bridging alkoxide groups and one — from the solvating alcohol molecule in the coordination sphere. The molecule is additionally supported by a hydrogen bond between the solvating alcohol and an oxygen atom belonging to the cage ligand coordinated by the other zirconium atom. The structures of produced silsesquioxanes display behavior typical for metal–organic frameworks as they crystallize initially as hexane clathrates, but lose the solvent on storage in inert atmosphere. This results in formation of empty channels situated along the c-axis.

New insight into the factors determining formation and stability of oxo-alkoxide carboxylates of titanium permits to design biocompatible systems for encapsulation of binary food quality inorganic dyes, such as Preussian blue, in a temperature-sensitive shell. The shells are formed spontaneously on hydrolysis of carboxylic acid-modified titanium alkoxides on the surface of water droplets containing the dye components. The complete dye is then prepared through mixing of pre-frozen encapsulated droplets which can be activated by heating to room temperature and also influenced by the storage time. The stable shells are obtained from longer chain carboxylates providing the micellar self-assembly derived constructions with increased colloid stability. The factors influencing the formation of individual crystalline oxo-alkoxide carboxylates—a process competing with the micellar self-assembly and decreasing the stability of the oxo-alkoxide carboxylate shells are discussed with the starting point in the molecular structures of the known compounds and also the new complexes Ti6O6(OAc)6(OiPr)6 · C6H14 (1) and Ti12O12(OAc)6(OnPr)18 (2).

Nanoparticles of a Nd-doped LaAlO(3) perovskite can be obtained rapidly and with quantitative yield using the Bradley (ether elimination) treatment of a mixture of individual Ln(2)Al(2)(O(i)Pr)(12)((i)PrOH)(2), Ln = La, Nd, in acetophenone. The initially produced particles are poorly crystalline, but their crystallinity improves strongly on heating to 800 degrees C, which leads also to a controllable aggregation. The prepared nanoparticles are rather solution stable and can easily be surface-modified, which opens prospects for their use as phosphors in bioimaging applications. The precursors, bimetallic isopropoxides of rare earth elements and aluminum with a 1:1 composition, Ln(2)Al(2)(O(i)Pr)(12)((i)PrOH)(2), can be prepared with high yields via direct dissolution of metallic lanthanoids in a solution of aluminum isopropoxide in a toluene-isopropanol medium or through a short time reflux of "Ln(O(i)Pr)(3)" with 1 equiv of Al(O(i)Pr)(3) in toluene. In spite of good volatility and their proper composition, the Ln(2)Al(2)(O(i)Pr)(12)((i)PrOH)(2), Ln = La, Nd, do not act as single-source precursors in MOCVD, because of their quantitative transformation into LnAl(3)(O(i)Pr)(12) together with Ln(5)O(O(i)Pr)(13) on evaporation. These molecules are, however, present intact in solution according to variable temperature NMR studies, which permits application of them successfully as single source precursors in the synthesis of Ln:LaAlO(3) perovskite nanopowders with compositions thoroughly controlled through the conditions of the synthesis. Luminescent properties of the Nd:LaAlO(3) were examined and discussed in detail. The thermal population of the (4)F(5/2) and (2)H(9/2) states was found as a consequence of the grain size effect causing difficulties in heat dissipation. Moreover, luminescence behavior of the powder annealed at a lowest temperature shows well-defined short-range order.

The reactions of Ga(acac)3 with salicylaldoxime (saoH2) and methyl-salicylaldoxime (Me-saoH2) in dichloromethane/hexane afforded the complexes [Ga(acac)(saoH)2] (1) and [Ga(acac)3][Ga(acac)(MesaoH)2] (2), respectively, in high yields. The crystal structures of 1 and 2 have been determined by single-crystal X-ray crystallography. Both complexes are mononuclear with the Ga(III) atoms being in octahedral environments surrounded by two bidentate chelate R-saoH− and one bidentate chelate acac− ligands. A [Ga(acac)3] moiety has co-crystallized along with the methylsalicylaldoximato complex. Characteristic IR as well as NMR data are discussed in terms of the nature of bonding in the structures of the two complexes. 1H and 13C NMR data in CDCl3 indicate that the salicylaldoximato complexes isomerize in solution.

The tetragonal BaTiO(3) nanopowder is synthesized in a solvent-less, efficient process by the thermolysis of a single [Ba(2)Ti(2)(thd)(4)(OnPr)(8)(nPrOH)(2)] precursor in a closed reactor at 700 degrees C under autogenous pressure, followed by combustion. This paper compiles the synthesis of the [Ba(2)Ti(2)(thd)(4)(OnPr)(8)(nPrOH)(2)] precursor, its analysis by mass spectrometry, and implementation for the fabrication of dielectric tetragonal BaTiO(3) nanopowder by controlled efficient thermal decomposition. The as-prepared, intermediate, and final forms of the obtained nanomaterials are systematically analysed by XRD, Raman, and EDS measurements to gain structural and compositional information. Employing HR-SEM, TEM, and HR-TEM techniques, the morphological changes during the structural evolution of all the phases are pursued. The mechanistic elucidation for the fabrication of BaTiO(3) nanopowder is developed on the basis of TGA and DTA data obtained for the initial [Ba(2)Ti(2)(thd)(4)(OnPr)(8)(nPrOH)(2)] reactant as well as the as-prepared BaCO(3) with amorphous Ti phase.

Long-term storage at 0 °C of a paraffin-sealed flask with commercial 70 wt% solution of zirconium n-propoxide in n-propanol resulted in crystallization of an individual oxoalkoxide complex Zr4O(OnPr)14(nPrOH)2 in over 20% yield. The structure of this molecule can be described as a triangular Zr3(μ3-O)(OR)10(ROH) core of 3 edge-sharing octahedrons with an additional Zr(OR)4(ROH) unit attached through a pair of (μ-OR) bridges. Mass spectrometric and 1H NMR investigation of the commercial samples of the most broadly applied zirconium and hafnium n-propoxides and n-butoxides indicate the presence of analogous species in the commercial alkoxide precursors. The content of oxo-alkoxide species in the commercial precursors has been estimated to be ~20% for n-propoxide and ~35% for zirconium n-butoxide. A new route has been presented for synthesis of the individual crystalline mixed ligand precursor [Zr(OnPr)(OiPr)3(iPrOH)]2, from zirconium n-propoxide. A high yield has been observed (~90%), indicative of an almost complete precursor transformation. Mass spectrometry has shown that the synthesized mixed ligand precursor is dimeric, which makes it an attractive alternative to zirconium n-propoxide. Addition of 1 eq of Acetylacetone to zirconium or hafnium alkoxide precursors results in formation of dimeric [M(OR)3(acac)]2 in high yields. These species have limited stability (much higher for Hf than for Zr) and transform in solution into hydrolysis-insensitive M(acac)4 through very unstable M(acac)3(OR) intermediates containing 7-coordinated metal centers. This transformation can be followed kinetically in hydrocarbon solvents by 1H NMR and is noticeably accelerated by addition of parent alcohols. The obtained results clearly reveal limited applicability of EXAFS and XANES techniques for the study of such systems, especially in the context of structure prediction. Electronic supplementary material The online version of this article (doi:10.1007/s10971-009-1988-0) contains supplementary material, which is available to authorized users.

The formation of nanoparticles in hydrolytic and non-hydrolytic reactions in organic media is treated as a borderline case of coordination chemistry equilibria. Metal cation complexes with O-donor ligands, such as metal alkoxides or β-diketonates and carboxylates, experience normally no kinetic hinders in re-structuring and aggregation. The steps of hydrolysis and condensation constitute in this case parts of one and the same kinetic phenomenon. Introduction of oxo-ligands during the first steps of hydrolytic or thermal decomposition leads thus in homogeneous processes to well-defined oligonuclear oxo-species. The structure of the latter is originating from the densest possible packing of cations and ligands and is not in any mean related to the structure of the original precursor molecules. The oxo-alkoxide molecules serve apparently as nuclei for the formation of larger aggregates that become phase separated and can be referred to as Micelles Templated by Self-Assembly of Ligands. The core of the latter is practically always crystalline or at least short-order organized, while the shell is, in the hydrolytic approach, constructed of hydrated amorphous oxide and ligands that stabilize the colloid via interaction with the solvent. The thermal treatment either in solution or for a dry xerogel is thus indispensable for preparation of fully crystalline particles and offers also an opportunity to control the final size of the particles via further aggregation. To guarantee the formation of complex oxide nanoparticles, the conditions insuring phase separation for each component have to be achieved. This means that the use of stoichiometric or super-stoichiometric quantities of water is required together with a solvent guaranteeing minimal solubility of hydrolyzed species. The approaches to complex oxide phases and oxides doped with lanthanide cations are discussed.

Modification of different zirconium propoxide precursors with H(2)dea was investigated by characterization of the isolated modified species. Upon modification of zirconium n-propoxide and [Zr(O(n)Pr)(O(i)Pr)(3)((i)PrOH)](2) with (1/2) a mol equivalent of H(2)dea the complexes [Zr(2)(O(n)Pr)(6)(OCH(2)CH(2))(2)NH](2) (1) and [Zr(2)(O(n)Pr)(2)(O(i)Pr)(4)(OCH(2)CH(2))(2)NH](2) (2) were obtained. However, (1)H-NMR studies of these tetranuclear compounds showed that these are not time-stable either in solution or solid form. The effect of this time instability on material properties is demonstrated by light scattering and TEM experiments. Modification of zirconium isopropoxide with either (1/2) or 1 equivalent mol of H(2)dea results in formation of the trinuclear complex, Zr{eta(3)mu(2)-NH(C(2)H(4)O)(2)}(3)[Zr(O(i)Pr)(3)](2)(iPrOH)(2) (3) countering a unique nona-coordinated central zirconium atom. This complex 3 is one of the first modified zirconium propoxide precursors shown to be stable in solution for long periods of time. The particle size and morphology of the products of sol-gel synthesis are strongly dependent on the time factor and eventual heat treatment of the precursor solution. Reproducible sol-gel synthesis requires the use of solution stable precursors.

The paper represents a listing of results obtained by developing the original methods of controlled synthesis of cluster and mono-, bi- and trimetallic oxo-alkoxide derivatives of rhenium and d-elements of V–VI groups. The developed techniques of the synthesis of metal alkoxides include: (1) anodic dissolution of the metals in the alcohol media; (2) direct reaction of the rhenium (VII) oxide with alkoxide derivatives of the transition elements. By such techniques were obtained: Re4O4(OEt)12, Re4O6(OiPr)10; individual rhenium alkoxocomplexes: Re4O2(OMe)16, Re4O6(OMe)12, Re4O6−y(OMe)12+y; bimetallic ReMoO2(OMe)7, Re4−xMoxO6−y(OMe)12+y, Re4−xWxO6−y(OMe)12+y; Nb2(OMe)8(ReO4)2, Ta2(OMe)8(ReO4)2, Nb4O2(OMe)14(ReO4)2, Ta4O2(OMe)14(ReO4)2, Nb4O2(OEt)14(ReO4)2, Ta4O2(OEt)14(ReO4)2, alkoxocomplexes: Nb2−xTax(OMe)8(ReO4)2, Nb4−xTaxO2(OMe)14(ReO4)2, Nb4−xTaxO2(OEt)14(ReO4)2. All compounds mentioned above are characterized with X-ray single crystal study, IR-spectroscopy, DTG. It has been shown, that thermal decomposition of alkoxide derivatives in inert or hydrogen atmosphere leads to formation nano-size powders of individual rhenium and its alloys at low temperature. Thermal decomposition in air leads to formation individual metal oxides or its solid solutions. It has been demonstrated that the alkoxide derivatives could be promising precursors for next generation catalysts manufacturing.

Trimetallic oxoalkoxide complexes (Nb0.7Ta0.3)4O2(OMe)14(ReO4)2 (I), (Nb0.3Ta0.7)4O2(OMe)14(ReO4)2 (II) and (Nb0.5Ta0.5)4O2(OMe)14(ReO4)2 (III) were obtained by the interaction of rhenium heptoxide (VII) Re2O7 with niobium and tantalum alkoxides M2(OMe)10 (M=Nb, Ta) in toluene. The centrosymmetric molecules (I)–(III) can be considered as a product of condensation of two M2(OMe)9(OReO3) molecules with the formation of two oxo-bridges. The specific feature of the structure is the uneven distribution of metal atoms in the crystallographic positions, where one symmetry-independent position, connected via μ-O with a perrhenate ReO4− group, is predominantly occupied by niobium atoms, while the other one connected via alkoxide groups has a higher tantalum content. The distribution of Nb and Ta in the structure is truly even only for compound III. The niobium and tantalum content is varied to a different extent for I (less) and for II (more), which is apparently due to small differences in the sizes of these two cations, resulting in preferences for packing of different molecules in the structures. Thermal decomposition of (Nb1−xTax)4O2(OMe)14(ReO4)2 (x=0.3, 0.5, 0.7) in air leads to the formation of crystalline species of solid solutions based on tantalum and niobium oxides displaying semi-ordered pores with the size of 100−250 nm. In the dry nitrogen atmosphere, the decomposition leads to the amorphous complex oxides containing rhenium, niobium and tantalum.

Zirconia and titania nanoparticle sols were prepared, using either ligand-based precursor stabilization or acid stabilization routes. These sols were used to prepare microporous coatings on γ-alumina substrates. The acetylacetonate-based particles have very small hydrodynamic diameters (1–2 nm), which lead to sol intrusion into the supports. As a result no appropriate membrane layer was formed. A microemulsion-based zirconia sol leads to a membrane that was selective in pervaporation dehydration of a water/n-butanol mixture. An optimized membrane showed stable separation performance for 120 days with a high selectivity toward water. Permporometry and gas permeation results on a titania membrane based on an acid-stabilized sol not only show microporosity, but also a significant contribution from defect flow.

We have investigated the interaction of niobium and tantalum alkoxides with pinacol and are reporting here isolation and structural characterization of the products, attractive potential precursors of materials with hierarchical porosity. The general feature in the reactivity of alkoxide complexes with additional ligands is that stabilization of the complexes is achieved due to Bronsted acidity of the ligand and possibility of formation of hydrogen bonds in the structure. Presence of strong organic bases does not influence the complex formation. We were able to isolate, for example, highly moisture-sensitive ortho-pinacolates of Nb and Ta, M(O2C6H12)2(OC6H12OH), in the presence of excess of triethylamine. The earlier attempts to prepare these complexes were unsuccessful because of extremely high solubility and easy hydrolysis of these species. The first step in microhydrolysis of M(O2C6H12)2(OC6H12OH), M = Nb, Ta, independently of basicity of the medium provides M2O(O2C6H12)2(OC6H12OH)4, even those highly moisture-sensitive in solution. The general conclusion of this work is that the Lewis acidity and blocking of the coordination sites by bulky alkoxide ligands does not play any important role. The reactivity of the species is not in any way hindered by the complete blocking of the metal centers.

A new non-hydrolytic, alkoxide-based route was developed to synthesize iron oxide nanocrystals. Surfactant-free thermal decomposition of the iron 2-methoxy-ethoxide precursors results in the formation of uniform iron oxide nanocrystals with an average size of 5.6 nm. Transmission electron microscope study shows that the nanocrystals are protected against aggregation by a repulsive surface layer, probably originating from the alkoxy-alkoxide ligands. Addition of oleic acid resulted in monodisperse nanocrystals with an average size of 4 nm. Mossbauer analysis confirmed that the nanocrystals mainly consisted of maghemite. Analysis of the magnetic hysteresis loop measurements and the zero field and field cooled measurements displayed an excellent fit to established theories for single-domain superparamagnetic nanocrystals and the size of the magnetic domains correlated well to the crystallite size obtained from transmission electron microscope.

A series of new dimeric complexes with composition [Ln2(hfa)6(4-cpyNO)3] (2:3 adduct, Ln = SmIII–DyIII, TmIII) were synthesized and fully characterized. X-ray diffraction data of [Tb2(hfa)6(4-cpyNO)3]·CHCl3 confirmed the dimeric structure; Tb ions are nine-coordinated by six O atoms from three hfa− ligands and three O atoms from three bridging 4-cpyNO molecules. The photophysical properties (absolute quantum yields and luminescence lifetimes) of the EuIII and TbIII 2:3 adducts are presented and compared with those of the 2:2 adducts.

The synthesis of Ba–Ti precursors was achieved by a self-assembly synthesis starting from barium metal, titanium n-propoxide and 2,2,6,6-tetramethyl-heptanedione (Hthd) in nPrOH. The structure of the obtained Ba2Ti2(thd)4(OnPr)8(nPrOH)2 compound is of the M 2 M ′ 2 X 16 type—one of the most widespread for both the homo- and heterometallic tetranuclear alkoxide complexes. It remains unchanged in solution according to the NMR data, which are easily interpreted in terms of the same molecular structure as that revealed by crystallography for the solid state. In order to form BaTiO3 phase doped with 1% of the Eu3+ the heterometallic alkoxide complex of barium and titanium with the necessary amount of Eu dissolved in the reaction mixture were hydrolyzed by moist ethanol on reflux in 1 M solution in n-propanol. The obtained gels were dried in vacuum and have been heat treated at different temperatures (700–1100 °C). XRD measurements were performed in order to study the phase formation and grain size. TEM images have been taken for the morphology and grain size characterization. Emission spectra and decay times were measured for the description of the luminescence properties of the obtained system.

Bimetal alkoxo complexes of rhenium, niobium, and tantalum with the general formula M4O2(OR)14(ReO4)2, where M = Nb or Ta and R = Me or Et, were prepared in ∼80% yield by reacting niobium or tantalum alkoxide M(OR)5 (R = Me or Et) with rhenium heptoxide Re2O7 in toluene. Comparative analysis of the molecular structures of the complexes was carried out by means of single-crystal X-ray diffraction and IR spectroscopy. The effect of the organic ligand and crystallization temperature on the geometry of the perrhenate group was studied. The solubility of the aforementioned alkoxo complexes in organic solvents increases with increasing hydrocarbon chain length of the ligand.

Metathesis of solid GaCl 3 with NaOEt/EtOH (1:3) provided, after separation of the NaCl precipitate, a solution containing oxoalkoxide chloride complexes of gallium. Residues from evacuation of the latter were redissolved in either toluene/ MeCN (solution 1) or toluene/pyridine (solution 2). Storage of the first solution provided crystals of Ga 5 (μ 5 -O)(μ-OEt) 8 Cl 5 (1), and of the second solution - [Ga 12 (μ 4 -O)2(μ 3 -O) 5 (μ-OEt) 10 -Cl 12 Py 4 ]Py (2), both at room temperature and in relatively high yields. Compound 1 crystallizes as a vertically contracted tetragonal pyramid with the μ 5 -O ligand situated in the center of the equatorial plane defined by four trigonal bipyramidal coordinated gallium atoms. The axial Ga atom has octahedral coordination. All eight edges of the pyramid are capped by μ-OEt groups, and all the chloride ligands are situated in terminal positions. Crystals of [Ga 12 (μ 4 -O) 2 (μ 3 -O) 5 (μ-OEt) 10 Cl 12 Py 4 ]Py (2) contain two [Ga 5 (μ 4 -O) (μ 3 -O) 2 (μ-OEt) 5 -Cl 5 Py] fragments connected through a cyclic [Ga 4 (μ 3 -O) 5 -Cl 2 Py 2 ) unit with a μ 3 -O ligand in its center. Of the metal atoms, three possess tetrahedral, seven trigonal bipyramidal, and two octahedral coordination. The mass spectrum of 1 contains penta- and tetranuclear fragments. The spectrum of 2 contains heptameric fragments in addition to the pentanuclear fragments that are analogous to those in the spectrum of 1. The factors leading to formation of polymeric M(OR) n and related oligonuclear oxocomplexes are discussed.

The anodic dissolution of tin metal in absolute alcohols yields oxoalkoxides with the general formula Sn6O4(OR)4 (R = Me (1), Et (2), i-Pr (3)) and orthoalkoxides with the general formula Sn(OR)2 (R = n-Bu (4), C2H4OMe (5)). According to X-ray crystallographic data, the molecule of Sn6O4(OEt)4 (2) is an octahedral [Sn6] cluster with alternating oxo and OEt groups on its faces. The mass spectra of 1 and 2 indicate the presence of fragments of the hexanuclear oxoalkoxides.

Preparation of high purity dense coatings of perovskite materials, in particular (Ba,Sr)TiO 3 and Ba(Ti,Nb)O 3 , requires application of highly solution and even gas phase stable single-source precursors. We report here a new series of bimetallic alkoxide complexes of 1: 1 composition, M II 2 M V 2 (L) 2 (OEt) 12 (EtOH) n , M II = Sr, Ba, M V = Nb, Ta, L = 2,2,6,6-tetramethylheptanedionate (thd, n = 2) or isopropylacetoacetate ( i PrAcAc, n = 0). These products were characterized by X-ray single crystal study in the solid state for the Sr 2 Ta 2 (thd) 2 (OEt) 12 (EtOH) 2 as an example, and for all complexes by NMR in solution. Multivariate analysis of evaporation of these complexes by EI-mass spectrometry shows that they are transformed into gas phase in the molecular form and display high gas phase stability. TG measurements reveal them to be thermally stable up to at least 280 °C and decompose at higher temperatures in a single step without separation of the components. The precursor transformations in solutions (through microhydrolysis) have also been studied.

The continuous scaling down of devices dimensions, in silicon technology, imposes to replace silicon dioxide. Among the potential candidates for new capacitors, some perovskite structure materials (such as titanate or zirconate) show interesting characteristics. The first way to develop perovskite films is to use a mixture of two β-diketonates by varying the solution's cationic ratio. However, our previous results on SrZrO3 showed that a wide parametric study had to be carried on. Another way is to design novel heterometallic precursors that contain both cations on the same molecule. The ligands could be chosen so that peculiar evaporation and decomposition temperatures could be obtained. Thus, perovskite films (SrZrO3) were deposited on plane Si(1 0 0) substrates by direct liquid injection MOCVD from two original heterometallic precursors Sr2Zr2(OnPr)8(thd)4(nPrOH)2 and Sr2Zr2(thd)4(OiPr)8. The oxide films were deposited at substrate temperature ranging from 550 to 900 °C. At the lowest temperatures (550 and 600 °C) the as-deposited films were amorphous. After a postannealing at 700 °C for 1 h under N2/O2, the films deposited at 550 °C were crystallized in the SrZrO3 orthorhombic phase. Crystallographic and chemical structures were controlled applying grazing X-ray diffraction and infrared spectroscopy measurements. Results are discussed with respect to experimental synthesis conditions.

Niobium isopropoxide, Nb(OiPr)5, is an attractive precursor of simple and complex niobium oxides in sol-gel technology. This compound cannot, unfortunately, be obtained by alcohol interchange starting from linear chain homologues such as Nb(OMe)5 or Nb(OEt)5. The equilibrium in the latter reaction favours formation of mixed-ligand complexes, [Nb2(OR)2(OiPr)8], R = Me, Et. In particular, [Nb2(OMe)2(OPri)8] (1) has been isolated in high yield from repeated treatment of Nb2(OMe)10 with excess of isopropanol. The X-ray single crystal study reveals a dinuclear structure containing a pair of edge-sharing octahedra with methoxide ligands in the bridging position. Infrared (IR) and mass spectroscopy (MS) studies confirmed the incomplete ligand substitution. The 1H-NMR spectra suggest equilibrium between different molecular forms in solution. Solvothermal interaction of 1 with La chips in toluene/isopropanol media results in formation of a mixture of LaNb2(OiPr)13 and La2Nb4(μ4−O)4(OH)2(μ−OiPr)8(OiPr)8 (2).

Niobium and tantalum oxo-ethoxo-perrhenates, M 4 V O 2 ( OEt ) 14 ( ReO 4 ) 2 , are easily obtained in high yields via interaction of metal ethoxides, MV(OEt)5, with rhenium heptoxide, Re2O7, in hydrocarbon solvents. The complexes have good solubility in hexane and toluene and are stable in solution at room temperature. Their molecular structures are based on a tetranuclear M4(μ-O)2(μ-OR)4X12 core, X = OR, ReO4, composed of two pairs of edge-sharing octahedra joined via two almost linear oxo-bridges containing a rectangular flat M4-arrangement. The perrhenate ligands are attached in a centrosymmetric manner to the two opposite corners of the rectangle.

The thermal decomposition of a ZrTi2[(OC2H4)2NH]3(OC3H7)6 precursor by the RAPET (reaction under autogenic pressure at elevated temperature) method provided the formation of crystalline zirconium titanate nanoparticles. These as-prepared nanoparticles are embedded in a carbon shell, which can be removed completely by calcination at 500 °C under air for 3 h, resulting in pure white crystalline nanoparticles. At a reaction temperature of 700 °C, the nanoparticles are mainly ZrTi2O6 (srilankite), whereas at 800 °C, the product is predominately Zr5Ti7O24. The structural, morphological, compositional, magnetic, and AC electrical properties are measured for the as-prepared ZrTi2O6 embedded in carbon (ZTEC), as well as the crystalline ZrTi2O6 nanoparticles (ZTN) obtained after sintering. The reaction mechanism is based on the decomposition products containing pyrrol and pyrazine. The presence of these compounds provides an understanding of the decomposition of the diethanolamine ligands and the formation of the nanoparticles in general.

The modification of zirconium or hafnium alkoxides with diethanolamine, H2dea, leads to the formation of unique nona-coordinated M{μ-η3-NH(C2H4O)2}3 cores. The mechanism is used to develop a self-assembly approach to the first thermodynamically stable zirconium–titanium and hafnium–titanium precursors, Zr{μ-η3-NH(C2H4O)2}3[Ti(OiPr)3]2 (1) and Hf{μ-η3-NH(C2H4O)2}3[Ti(OiPr)3]2 (2). Mass spectrometric characterization of these compounds demonstrates their volatility. In addition to the solution stability of these compounds the volatility makes them attractive single source precursors for MOCVD and ALD applications. These precursors are also interesting candidates for application in sol–gel synthesis of microporous materials as the stability of the core prevents self-assembly of ligands on the outer surface of the primary particles formed during the hydrolysis. A n-propoxide analog of 1 can be prepared from zirconium n-propoxide but does not yield any crystalline material. It is demonstrated that 1 can be prepared from [Zr(OnPr)(OiPr)3(iPrOH)]2, however, with a lower yield compared to the use of zirconium isopropoxide. The single crystals obtained from systems containing zirconium isopropoxide, titanium isopropoxide and triethanolamine H3tea turned out to be Ti2(OiPr)2({μ-η4-NH(C2H4O)3}2)2 (4). Theoretical calculations indicate that the octacoordinate M{μ-η4-N(C2H4O)3}2 core, anticipated in reaction with H3tea, will have metal–nitrogen bonds that are too long for its stabilization. This explains why the formation of 4 is thermodynamically favored over the formation of heterometallic species.

Herein, we report a new method for the crystal growth of two Zn-based MOFs at room temperature (known MOF-5 and a new modification of [{Zn2(TBAPy)(H2O)2}·3.5DEF]n (1)) by employing slow diffusion conditions. Employing both Zn-based MOFs with different pore morphology made it possible to discover an anomalous adsorption of L-histidine in of up to 24.3 × 10(15) molecules cm(-2) at 25 °C. This is one of the first reports aimed not only at describing a new method for the targeted formation of crystalline MOFs and coordination polymers, but also at demonstrating the use of Zn-based MOFs as potential drug delivery materials, with highly effective adsorption of l-histidine given herein as an example.

Magnetic nanoparticles modified with siloxane layers bearing amino and thiol functions have been used for immobilization of urease either by adsorption or via surface grafting. The activity of the immobilized enzyme in the hydrolysis of urea extended to the levels typical of the native enzyme, while its long-term stability in combination with magnetic retraction opened for its repeated use in both analysis and detoxification of bio-fluids. The immobilized urease revealed strongly enhanced stability and 65% activity in the presence of 0.1mmol/l of Hg(2+) or 0.3mmol/l of Cu(2+) while the native urease did not retain any activity at all. The enzyme grafting was shown to be a potentially perspective tool in alleviation of heavy metal poisoning and to be providing an opportunity for use of the developed adsorbents as both biosensors and bio-reactants for removal of urea from biofluids.

A novel use of Titania nanoparticles as agents in the nano interface interaction between a beneficial plant growth promoting bacterium (Bacillus amyloliquefaciens UCMB5113) and oilseed rape plants (Brassica napus) for protection against the fungal pathogen Alternaria brassicae is presented. Two different TiO2 nanoparticle material were produced by the Sol-Gel approach, one using the patented Captigel method and the other one applying TiBALDH precursor. The particles were characterized by transmission electron microscopy, thermogravimetric analysis, X-ray diffraction, dynamic light scattering and nano particle tracking analysis. Scanning electron microscopy showed that the bacterium was living in clusters on the roots and the combined energy-dispersive X-ray spectroscopy analysis revealed that titanium was present in these cluster formations. Confocal laser scanning microscopy further demonstrated an increased bacterial colonization of Arabidopsis thaliana roots and a semi-quantitative microscopic assay confirmed an increased bacterial adhesion to the roots. An increased amount of adhered bacteria was further confirmed by quantitative fluorescence measurements. The degree of infection by the fungus was measured and quantified by real-time-qPCR. Results showed that Titania nanoparticles increased adhesion of beneficial bacteria on to the roots of oilseed rape and protected the plants against infection.

Nanocomposite dermal drug delivery systems based on cellulose nanofibers with grafted titania nanoparticles loaded by two antibiotic medicines from different classes, i.e. tetracycline (TC) and phosphomycin (Phos), were successfully produced by a ‘‘green chemistry’’ approach in aqueous media. The influence of a different surface binding mechanism between the drug molecule and modified cellulose nanofibers on the release of the drug and, as a result, on antimicrobial properties against common pathogens Gram-positive, Staphylococcus aureus and Gram-negative Escherichia coli was investigated. The disk diffusion method and broth culture tests using varying concentrations of drugs loaded to nanocomposites were carried out to investigate the antibacterial effects. The influence of UV irradiation on the stability of the obtained nanocomposites and their antibacterial properties after irradiation were also investigated, showing enhanced stability especially for the TC loaded materials. These findings suggest that the obtained nanocomposites are promising materials for the development of potentially useful antimicrobial patches.

Uniform nanocrystalline mesoporous mixed cobalt–nickel spinel phases displaying unimodal pores in the 7–12 nm range and relatively high specific surface areas up to 83 m2/g were prepared by a novel low temperature synthesis approach in which the desired metal oxide stoichiometries were introduced on a molecular level by reacting heterometallic alkoxide precursors in the presence of supramolecular liquid crystalline phases. The resultant phases, composed mainly of ca. 8–11 nm uniform cobalt–nickel spinel nanoparticles, were highly promising as low-temperature hydrocarbon combustion catalysts investigated in a model reaction of propane oxidation. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

Dissolution of BaO in 90–95% MeOH provides [Ba(OH)2(H2O)2](MeOH)2 (1) as rectangular platelet crystals. Interaction of BaO or Ba(OH)2 with 98–100% methanol results in the formation of needle shaped crystals of [Ba(OH)2(MeOH)2](MeOH) (2). The structure of 1 is composed of planar layers of tetragonally distorted [Ba(OH)4/2(H2O)4/2] cubes altered by the layers of alcohol molecules oriented in the direction perpendicular to the metal hydroxide layers. The structure of 2 is formed by layers of distorted antiprisms of Ba(μ3-ROH)(μ-OH)4(μ-ROH)2(ROH)] and [Ba(μ3-ROH)2(μ-ROH)2(μ-OH)4] composition. IR spectra of 1 and 2 are in good agreement with the observed structures. The structures of compounds 1 and 2 are compared with those of Ba(OH)2 · nH2O (n = 1, 3).

Ionic or ionogenic alkoxides are attractive potential catalysts for polymerization reactions. Direct interaction between CoCl2 and [Ta(OMe)5] produced, by self-assembly, a small amount of ionic aggregate clathrate with acetonitrile, [ Co 2 Ta 2 ( OMe ) 12 ( MeCN ) 4 ] 2 + [ CoCl 3 ( MeCN ) ] 2 - · 2 MeCN ( 1 ) . The structure of 1 contains a planar M4(μ3-OR)2(μ-OR)4-core that can be considered as a fragment of hexagonal packing of metal and ligand atoms completed by 6 (3 + 3) terminal alkoxide ligands at the tantalum and 4 (2 + 2) terminal acetonitrile molecules at the cobalt atoms that are bearing the (+1) positive charge each. A rational synthesis of this compound was achieved by reaction between [NaTa(OMe)6] with four equivalents of CoCl2 in toluene/acetonitrile to give a new crystallographic form [Co2Ta2(OMe)12(MeCN)4] [CoCl3(MeCN)]2 (2), not containing interstitial solvent molecules.

The modification of different zirconium propoxide and hafnium propoxide precursors with 2,2,6,6,-tetramethyl-3,5-heptanedione (Hthd) was investigated by characterization of the isolated modified species. The complexes [Zr(OnPr)3(thd)](2), [Zr(OnPr)(OiPr)2(thd)]2, Zr(OiPr)(thd)3, [Hf(OnPr)3(thd)]2, and Hf(OiPr)(thd)3 were isolated and characterized. The structure of the n-propoxide analogue of Zr(OiPr)(thd)3 could not be refined, but its existence was clearly demonstrated by XRD and 1H NMR. The modification of the propoxide precursors involves mono- and trisubstituted intermediate compounds and does not involve a disubstituted compound; thus, the commercial product that is claimed to be "Zr(OiPr)2(thd)2" and is most commonly used for the MOCVD preparation of ZrO2 does not exist. No evidence was found for the presence of such a compound in either zirconium- or hafnium-based systems. Formation of the dimeric hydroxo-di-thd-substituted complex, [Hf(OH)(OiPr)(thd)2]2, which could be isolated only for hafnium-based systems, occurs on microhydrolysis. All heteroleptic intermediates are eventually transformed to the thermodynamically stable Zr(thd)4 or Hf(thd)4) The compounds obtained from isopropoxide precursors showed a higher stability than those with n-propoxide ligands or a combination of both types. In addition, it is important to note that residual alcohol facilitates the transformation and strongly enhances its rate. The unusually low solubility and volatility of MIV(thd)4 has been shown to be due to close packing and strong van der Waals interactions in the crystal structures of these compounds.

The synthesis and structural determination of three new heterometallic molybdenum complexes, one with cobalt and two with nickel and two of these with -diketonate ligands and one with amino alcohol ligands, are presented. The reaction of cobalt acetylacetonate with [MoO(OMe)4] provides [Co2Mo2O2(acac)2(OMe)10] (1) and [MoO(acac)(OMe)3] (4),and the reaction of nickel acetylacetonate with [MoO(OMe)4]provides [Ni2Mo2O2(acac)2(OMe)10] (2) and 4. The reaction of [Ni(ORN)2] (RN = CHMeCH2NMe2) with [MoO(OMe)4] yields [Ni2Mo2O2(ORN)2(OMe)10] (3). The two new oxomolybdenum complexes undergo ether elimination upon storage to give the corresponding dioxo complexes [MoO2(acac)(OMe)]2 (5) and [MoO2(ORN)(OMe)]2 (6). Compounds 3 and 4 could also be obtained from the reaction of stoichiometric amounts of Hacac with [MoO(OMe)4] and [MoO2(OMe)2], respectively. The local structure around the nickel atom in compound 2 in solution and compound 3 in the solid state and in toluene/hexane solution has been determined by means of EXAFS spectroscopy. The complexes are intended to be used as single-source precursors, which are attractive in coatings and for the preparation of mesoporous materials; its application for the synthesis of nickel molybdate by sol-gel processing is therefore reported. The oxide material obtained from 3 displays a uniform grain size and a large surface area.

The binding and release of trivalent rare earth element (REE) cations (Dy(3+), Nd(3+) and La(3+)) from solutions by a new fully characterized magnetic nano adsorbent material, consisting of iminodiacetic acid ligand (H2IDA) grafted onto SiO2 covered γ-Fe2O3 nanoparticles, was investigated. The nano adsorbent revealed a slightly higher capacity towards heavier REE and appreciable selectivity, especially on desorption. It was found that the composition of the surface complex was RE(3+) : L = 1 : 1. The complexation of the molecular H2IDA with RE(3+) in this ratio under non-basic conditions was therefore investigated by X-ray crystallography to produce relevant molecular models. Unexpectedly big differences in coordination numbers and binding mode of IDA along with distinct analogies in packing of the ligand molecules in the obtained 2D-coordination polymer structures provided valuable insights into possible reasons for the observed selectivity.

Modification of the liquid Ni(ORN)2, RN = C2H4NMe2, with stoichiometric or sub-stoichiometric amounts of carboxylic acids, HCOOH or CH3COOH, results in formation of crystalline heteroleptic complexes Ni6(OH)2(ORN)6(OCOR)2, R = H (1), CH3 (3) with the core structure closely analogous to that observed earlier for hexanuclear titanium (IV) alkoxide carboxylates and derived from hexagonal packing of the donor atoms.

Interaction of FeX 3 , X = Cl, Br with 3 equiv. of NaOEt in toluene/ethanol media provides mixtures of iron (III) oxoethoxide, Fe 5 O(OEt) 13 , and its halide alkoxide analogs. The latter have been identified by mass-spectrometric study as Fe 5 O(OEt) 12 X and Fe 5 O(OEt) 11 X 2 . Application of FeBr 3 as a starting material leads to much more pure samples of Fe 5 O(OEt) 13 isolated with higher yields.

We present the results of the RAPET (reaction under autogenic pressure at elevated temperatures) dissociation of CoZr(2)(acac)(2)(O(i)Pr)(8) at 700 degrees C in a closed Swagelok cell under an applied magnetic field of 10 T. It produces a mixture of carbon-coated and noncoated metastable ZrO(2) nanoparticles, bare metallic Co nanoparticles, and bare carbon. The same reaction in the absence of a magnetic field produces spherical Co and ZrO(2) particles in sizes ranging from 11 to 16 nm and exhibiting, at room temperature, metastable phases: fcc for cobalt and a tetragonal phase for zirconia. The metastable phases of Co and ZrO(2) are manifested because of a carbon shell of approximately 4 nm thickness anchored to their surfaces. The effect of an applied magnetic field to synthesize morphologically different, but structurally the same, products is the key topic of the present paper.

The article describes the principles of the Single Source Precursor approach to inorganic materials and introduces the Geometrical Molecular Structure Design Concept (MSDC) based on the choice of a proper molecular structure type for the desired precursor and completing it with ligands providing both the necessary number of donor atoms and the sterical protection of the chosen core. Application of MSDC is illustrated with examples taken from development of new approaches in the synthesis of oxide and sulfide catalysts and ferroelectric oxide materials.

The thermal decomposition of the methoxide complexes MoO(OMe)4 (I), Re4O6(OMe)12 (II) and (Re1−xMox)O6(OMe)12 (0.24≤x≤0.55) (III) in hydrogen and nitrogen at T≤800 °C and in air at temperatures T≤400 °C have been monitored by thermal analysis, X-ray powder diffraction and scanning electron microscopy. Heating of I, II and III in air yields orthorhombic MoO3, ReO3 and a mixture of these two phases, respectively. Thermal treatment of I and II in nitrogen, using heating rates of 20 K min−1 or faster, yields the same products as in air, while applying slower heating rates of I and thermal treatment of III in nitrogen yield the tetragonal modification of MoO2 and (Re1−xMox)O2 (with 0.24≤x≤0.55), respectively. Heat treatment of I, II and III in hydrogen yields fine powders of Mo, Re or a Re–Mo alloy (having the structure of the σ-phase) at surprisingly low temperatures, around 520, 240 and 360 °C for I, II and III, respectively.

Interaction of Ni(acac)2 with 2 eq. of Al(OiPr)3 in toluene on reflux with subsequent modification with 2 eq. of acetylacetone offers with quantitative yields a new heterometallic complex, NiAl2(acac)4(OiPr)4 (1), characterized by X-ray single crystal study and variety of spectroscopic techniques. Uniform NiAl2O4-coatings were obtained on Al2O3 substrates by dip-coating from toluene solutions of 1 with subsequent thermal treatment and characterized by X-ray powder, SEM and AFM studies. Powder samples were obtained by hydrolysis of solutions of 1 in the moist air and characterized by TG and X-ray powder data.

Rhenium and molybdenum oxomethoxide complexes Re 2O3(OMe)6, ReMoO2(MeO)7, and Mo2O2(OMe)8 were used as precursors to prepare highly dispersed mono and bimetallic oxide species supported on the microporous NaY zeolite and mesoporous SiO2 and Al2O3. The prepared materials were characterized by the use of FTIR, NH3-TPD, and H2-TPR techniques. It was shown that, upon loading into microporous zeolite, oxomethoxide complexes loose their ligands so that just metal suboxide cores remains in the intracrystalline voids as the nanosized oxide clusters. The obtained clusters reveals both acidic and redox properties. The maximum amount of NH3 adsorbed per bimetallic species could be used as a characteristic of both availability of acid sites and oxide dispersion. Reducibility of these species depends strongly on both their location in the matrix and the size. The matrix texture also affects the transitions between different valent states of Re and Mo as well as the metal reduction extent. © 2004 Elsevier B.V. All rights reserved.

Heterometallic nanocomposite oxide catalysts have been obtained by impregnation of NaY zeolite with toluene solutions of a structurally characterized heterometallic heteroleptic alkoxide, Co2Nb2(acac)2(OMe)12. EXAFS studies showed the molecular structure of the complex to be preserved and the coordination of the late transition metal atom in the ready nanocomposite very close to that in the original complex. A silsesquioxane complex has been used in order to prepare a zeolite nanocomposite analogue and this proved successful with very similar EXAFS spectra to the ready nanocomposite, indicating the usefulness of the silsesquioxanes as molecular analogues of zeolites.