Titanium Oxo Cluster Research Articles

New hybrid core–shell star-like architectures made of poly(n-butyl acrylate) grown from well-defined titanium oxo-clusters

New hybrid star-like macromolecular objects have been designed from an inorganic multifunctional platform following two routes. The first one consists of the direct introduction of polymer arms at the surface of the titanium oxo-cluster [Ti16O16(OEt)32] by alkoxide exchange. The second approach corresponds to the growth by Atom Transfer Radical Polymerization (ATRP) of n-butyl acrylate from the macroinitiator [Ti16O16(OEt)26(OCH2CCl3)6]. By crossing different characterization techniques and methodologies (single crystal X-ray diffraction, 13C and 17O NMR and 1H DOSY NMR spectroscopy, Size Exclusion Chromatography), evidence of the formation of such macromolecular compounds is reported.

A New Photoactive Crystalline Highly Porous Titanium(IV) Dicarboxylate

Titanium is a very attractive candidate for MOFs due to its low toxicity, redox activity, and photocatalytic properties. We present here MIL-125, the first example of a highly porous and crystalline titanium(IV) dicarboxylate (MIL stands for Materials of Institut Lavoisier) with a high thermal stability and photochemical properties. Its structure is built up from a pseudo cubic arrangement of octameric wheels, built up from edge- or corner-sharing titanium octahedra, and terephthalate dianions leading to a three-dimensional periodic array of two types of hybrid cages with accessible pore diameters of 6.13 and 12.55 A. X-ray thermodiffractometry and thermal analysis show that MIL-125 is stable up to 360 degrees C under air atmosphere while nitrogen sorption analysis indicates a surface area (BET) of 1550 m(2) x g(-1). Moreover, under nitrogen and alcohol adsorption, MIL-125 exhibits a photochromic behavior associated with the formation of stable mixed valence titanium-oxo compounds. The titanium oxo cluster are back oxidized in the presence of oxygen. This photochemical phenomenon is analyzed through the combined use of Electron Spin Resonance (ESR) and UV-visible absorption spectroscopies. The photogenerated electrons are trapped as Ti(III) centers, while a concomitant oxidation of the adsorbed alcohol molecules occurs. This new microporous hybrid is a very promising candidate for applications in smart photonic devices, sensors, and catalysis.

Dielectric investigation of organic–inorganic hybrid based on titanium oxocluster-crosslinked elastomer

Abstract In this paper, we have prepared new type of organic–inorganic hybrid materials based on covalent bond between the two constituents: elastomer and titanium oxocluster. Commercial hydrogenated acrylonitrile-butadiene rubber (HNBR)-Therban ® 3407 was selected as the matrix for mixing the titanium oxocluster. Three different samples containing the elastomer and peroxide, elastomer, peroxide and titanate, and elastomer and titanate, respectively were prepared. The dielectric permittivity have been scanned over a wide range of frequencies and temperatures in order to determine the how the titanate and the peroxide influences the molecular mobility. Complementary DSC and mechanical analysis were performed. We found that the presence of titanates-compounds strongly influences the mobility of the ions and it’s reflected in the low activation energy for the ionic conductivity. In spite that the glass transition temperature is held constant, the temperature dependence of the α process, as well as the free volume at the glass transition, the fragility parameter and the ΔCp during the glass transition are strongly influenced by the composition.

Titanium Oxo-Clusters: Vesatile Nano-Objects for the Design of Hybrid Compounds

ABSTRACTThe description of three titanium oxo-clusters and their use as inorganic components of hybrid organic-inorganic materials are reported. The first approach consists to add titanium oxo-clusters, [Ti6O4(C6H5COO)8(OPrn)8], in an ORMOCER⊗ based hybrid medium. Nano-sized titanium oxo-clusters combined with the chemical nature of the components, allow the tuning of the optical properties, especially the refractive index. The second approach consists to associate functionalized titanium oxo-clusters to elaborate hybrid materials with perfectly defined inorganic domains. The more relevant example of titanium oxo-cluster to build hybrid networks from nano-building blocks is the oxo-cluster [Ti16O16(OEt)32]. Indeed, the nature and the number of functional groups at the surface of these metallic oxo-clusters can be tuned in order to generate cross-linking agents of organic polymers. The studies of the structure-property relationships of the resulting nanocomposites have been investigated. Finally the structure of a purely carboxylate oxo-clusters is briefly described. This new family of stable oxo-clusters opens the way for the production of original hybrid compounds.

New hybrid organic–inorganic nanocomposites based on functional [Ti16O16(OEt)24(OEMA)8] nano-fillers

New hybrid nanocomposites based on a methacrylate functionalized titanium-oxo cluster as nano-cross-linker show improved mechanical properties, optical transparency and photochromic activity.

Preparation of a highly active nanocrystalline TiO 2 photocatalyst from titanium oxo cluster precursor

Nanocrystalline TiO 2 (sample S1) was prepared from a titanium oxo cluster (Ti 7O 4(OEt) 20) precursor via a sol–gel route. This photocatalyst showed a higher photocatalytic activity than the TiO 2 (sample S2) obtained from titanium tetraisopropoxide. The samples were characterized by thermal analysis (TGA/DSC), X-ray diffraction, micro-Raman spectroscopy, transmission electron microscopy, N 2 adsorption (BET surface area), infrared absorption spectroscopy (FT-IR) and X-ray photoelectron spectroscopy. The characterization results show that both samples are anatase nanocrystals with particle sizes of about 12 nm, but the more photocatalytically active sample S1 has more surface hydroxyl groups and larger surface area and pore volume than sample S2.

Preparation of a highly active nanocrystalline TiO2 photocatalyst from titanium oxo cluster precursor

Nanocrystalline TiO2 (sample S1) was prepared from a titanium oxo cluster (Ti7O4(OEt)20) precursor via a sol–gel route. This photocatalyst showed a higher photocatalytic activity than the TiO2 (sample S2) obtained from titanium tetraisopropoxide. The samples were characterized by thermal analysis (TGA/DSC), X-ray diffraction, micro-Raman spectroscopy, transmission electron microscopy, N2 adsorption (BET surface area), infrared absorption spectroscopy (FT-IR) and X-ray photoelectron spectroscopy. The characterization results show that both samples are anatase nanocrystals with particle sizes of about 12 nm, but the more photocatalytically active sample S1 has more surface hydroxyl groups and larger surface area and pore volume than sample S2.

Nanometric monodispersed titanium oxide particles on mesoporous silica: synthesis, characterization, and catalytic activity in oxidation reactions in the liquid phase

Subnanometric monodispersed titanium oxide particles have been dispersed on the surface of a large mesopore SBA-15 silica. TiSBA-15 materials were obtained by reaction between a hexanuclear titanium oxo cluster and a calcined SBA-15 silica in solution. Solids with various Ti loading have been prepared and characterized by chemical analysis, X-ray diffraction, nitrogen adsorption, and UV–visible spectroscopy. Titanium oxide particles containing 6 Ti octahedra show a UV–visible absorption band at ca. 235 nm, close to those usually observed on TiMCM-41 or TiHMS materials obtained by direct synthesis. The catalytic performance of TiSBA compounds has been evaluated in a series of oxidation reactions with H 2O 2 or TBHP as oxygen donors and compared with that of TiHMS materials obtained by direct synthesis. Data indicate that TiO 2 nanoparticles are active and selective in epoxidation of cyclohexene and in oxidation of aniline and aromatic molecules. Activities and selectivities suggest that isolated tetrahedrally coordinated Ti species are not necessarily the only active species for these reactions. Moreover, results raise the problem of the validity of such oxidation reactions as a test for the determination of the coordination state of Ti species.

Synthesis of new titanium–oxo cluster compounds: X-ray structure of the tetranuclear oxide [Ti4Cl6(µ2-O2CPh)6(µ3-O)2

Titanium–oxo cluster compounds can be obtained in high yields by the action of carboxylic acids on titanium tetrachloride; X-ray structure analysis of the benzoate derivative [Ti4Cl6(µ2-O2CPH)6(µ3-O)2] reveals the presence of a previously unknown Ti4O2 core structure.