Bogdan Moraru

Methacrylate‐Substituted Mixed‐Metal Clusters Derived from Zigzag Chains of [ZrO8]/[ZrO7] and [TiO6] Polyhedra

Reaction of titanium butoxide and zirconium butoxide with methacrylic acid in different molar ratios results in the formation of the mixed-metal clusters Ti4Zr4O6(OBu)4(OMc)16, Ti2Zr4O4(OBu)2(OMc)14, Ti4Zr2O4(OBu)6(OMc)10, and Ti2Zr6O6(OMc)20 (OMc = methacrylate). The molecular structures of these clusters have been determined by single-crystal X-ray diffraction analysis. They are based on a common structural motif, namely a zigzag chain comprising two terminal [TiO6] octahedra and two or four central [ZrO8] dodecahedra or [ZrO7] pentagonal bipyramids sharing common edges. Two additional [TiO6] octahedra or [ZrO8] dodecahedra are condensed at the flank of the main chain.

A molecular approach to RuO2-based thin films: sol–gel synthesis and characterisation

Abstract RuO2-based materials are attractive candidates for a variety of technological applications, especially in catalysis and electrocatalysis. In this field, much research is nowadays focused on the development of nanosystems, especially as thin layers, with tailored compositional and microstructural properties. In the present study, RuO2-based coatings were prepared by a sol–gel route. RuO2 nanocrystalline films were obtained by dip-coating from alcoholic solutions of Ru(OEt)3 and subsequent thermal treatments in air or N2 between 100 and 400 °C. Mixed RuO2–SiO2 coatings were synthesised starting from solutions of RuCl3 and [NH2(CH2)2NH(CH2)3Si(OMe)3]. The silicon compound was used either as precursor for the silica matrix or as complexing agent for the Ru ions, to synthesise ruthenium oxide-based nanoaggregates directly in the SiO2 glass. The microstructure of the systems was studied by X-ray diffraction, while their surface and in-depth chemical composition was analysed by X-ray photoelectron spectroscopy. Furthermore, the thermal evolution of RuO2–SiO2 coatings was investigated by optical absorption.

Cross-linking of poly(methyl methacrylate) by oxozirconate and oxotitanate clusters

Radical polymerization of methyl methacrylate with 0.5 - 2 mol% of the (meth)acrylate-substituted oxozirconium and oxotitanium clusters Zr 6 (OH) 4 O 4 (OMc) 12 (OMc = methacrylate), Zr 4 O 2 (OMc) 12 , Ti 6 O 4 (OEt) 8 (OMc) 8 and Ti 4 O 2 (OPr 1 ) 6 (OAcr) 6 (OAcr = acrylate) results in an efficient cross-linking of the organic polymers. The obtained inorganic-organic hybrid polymers exhibit a higher thermal stability due to inhibited depolymerization reactions. Contrary to undoped poly(methyl methacrylate), the cluster cross-linked polymers are insoluble but swell in organic solvents. The solvent uptake upon swelling decreases with an increasing amount of polymerized cluster. The impedance spectra of PMMA doped with various proportions of Zr 4 O 2 (OMc) 12 show that the capacitance of the polymers decreases with an increasing proportion of the cluster. The polymer doped with 2 mol% of Zr 4 O 2 (OMc) 12 shows an increase in conductivity to 0.9.10 -7 S.cm -1 at 74 °C.

Degradation of a methacrylate-substituted oxozirconium cluster by acetylacetone

Abstract Reaction of Zr4O2(OMc)12 (OMc=methacrylate) with acetylacetone leads to the degradation of the cluster and formation of monomeric Zr(acac)2(OMc)2 (acac=acetylacetonate). The zirconium atom in Zr(acac)2(OMc)2 is dodecahedrally coordinated by the eight oxygen atoms of the chelating OMc and acac ligands.

EXAFS investigations on nanocomposites composed of surface-modified zirconium and zirconium/titanium mixed metal oxo clusters and organic polymers

Summary. The surface-modified oxometallate clusters Zr6(OH)4O4(OMc)12, Ti4Zr4O6(OBu)4 (OMc)16, and Ti2Zr4O4(OBu)2(OMc)14 (OMc = methacrylate) as well as their nanocomposites with polystyrene, poly(methacrylic acid) and poly(methyl methacrylate) were investigated by EXAFS. Studies on the nanocomposites revealed that the structure of the cluster core is retained in the hybrid materials.

Inorganic-Organic Hybrid Polymers from Surface-Modified Oxometallate Clusters

Inorganic-organic hybrid polymers were prepared by radical polymerization of methacrylic acid or methyl methacrylate with the (meth) acrylate-substituted oxozirconium and oxotitanium clusters Zr 6 (OH) 4 O 4 (OMc) 12 (OMc = methacrylate), Zr 4 O 2 (OMc) 12 , Ti 6 O 4 (OEt) 8 (OMc) 8 and Ti 4 O 2 (OPr i ) 6 (OAcr) 6 (OAcr = acrylate). A few mol% of cluster is sufficient for an efficient cross-linking of the polymer chains. Small-angle X-ray scattering data indicate that the cluster size is retained in the polymers and that the microstructure of the cluster cross-linked samples can be described by a dispersion of identical spherical or disk-shaped clusters in the polymer. The obtained hybrid polymers exhibit a higher thermal stability because depolymerization reactions are inhibited. Contrary to undoped poly (methyl methacrylate), the cluster cross-linked polymers are insoluble but swell in organic solvents. The solvent uptake upon swelling decreases with an increasing amount of polymerized cluster.