François Ribot

Molecular design of hybrid organic-inorganic nanocomposites synthesized via sol-gel chemistry

The design, synthesis and some optical properties of hybrid organic-inorganic nanocomposites materials are presented. The properties that can be expected for such materials depend on the chemical nature of their components, but they also depend on the synergy of these components. Thus, the interface in these nanocomposites is of paramount significance and one key point of their synthesis is the control of this interface. These nanocomposites can be obtained by hydrolysis and condensation reactions of organically functionalized alkoxide precursors. Striking examples of hybrids made from modified silicon, tin and transition metal alkoxides are presented. Some optical properties (photochromic, luminescence, NLO) of siloxane based hybrids are also discussed.

Synthesis and characterization of crystalline tin oxide nanoparticles

Monodisperse non-aggregated spheroidal nanoparticles of SnO2 cassiterite are prepared through hydrolysis of tin isopropoxide in the presence of acetylacetone and p-toluenesulfonic acid, followed by ageing at 60 °C. The obtained sols remain stable for several months at 4 °C. The nanoparticles have been characterized in the solid state (xerosol) by powder X-ray diffraction, TEM, FTIR, TGA-DTA, and 119Sn MAS and 13C CP-MAS NMR. The mean size of the cassiterite oxide core is about 1–2 nm. These particles do not aggregate in suspension because their surfaces are protected by an hybrid organic–inorganic layer containing acetylacetonate ligands, acetylacetone, p-toluenesulfonates and water.

A Top‐Down Synthesis Route to Ultrasmall Multifunctional Gd‐Based Silica Nanoparticles for Theranostic Applications

New, ultrasmall nanoparticles with sizes below 5 nm have been obtained. These small rigid platforms (SRP) are composed of a polysiloxane matrix with DOTAGA (1,4,7,10-tetraazacyclododecane-1-glutaric anhydride-4,7,10-triacetic acid)-Gd(3+) chelates on their surface. They have been synthesised by an original top-down process: 1) formation of a gadolinium oxide Gd2O3 core, 2) encapsulation in a polysiloxane shell grafted with DOTAGA ligands, 3) dissolution of the gadolinium oxide core due to chelation of Gd(3+) by DOTAGA ligands and 4) polysiloxane fragmentation. These nanoparticles have been fully characterised using photon correlation spectroscopy (PCS), transmission electron microscopy (TEM), a superconducting quantum interference device (SQUID) and electron paramagnetic resonance (EPR) to demonstrate the dissolution of the oxide core and by inductively coupled plasma mass spectrometry (ICP-MS), mass spectrometry, fluorescence spectroscopy, (29)Si solid-state NMR, (1)H NMR and diffusion ordered spectroscopy (DOSY) to determine the nanoparticle composition. Relaxivity measurements gave a longitudinal relaxivity r1 of 11.9 s(-1)  mM(-1) per Gd at 60 MHz. Finally, potentiometric titrations showed that Gd(3+) is strongly chelated to DOTAGA (complexation constant logβ110 =24.78) and cellular tests confirmed the that nanoconstructs had a very low toxicity. Moreover, SRPs are excreted from the body by renal clearance. Their efficiency as contrast agents for MRI has been proved and they are promising candidates as sensitising agents for image-guided radiotherapy.

Synthesis through an in situ esterification process and characterization of oxo isopropoxo titanium clusters

Three titanium oxo-isopropoxo clusters Ti 6 O 4 (OOCCH 3 ) 4 (OPr 1 ) 12 ( 1 ), Ti 12 O 16 (OPr 1 ) 16 ( 2 ) and Ti 12 O 16 (OPr 1 ) 16 ·1.4CH 2 Cl 2 ( 3 ) are obtained by refluxing Ti(OPr 1 ) 4 with 1.2 equivalents of carboxylic acids over two days. The molecular structures of Ti 6 O 4 (OOCCH 3 ) 4 (OPr 1 ) 12 ( 1 ) and Ti 12 O 16 (OPr 1 ) 16 · 1.4CH 2 Cl 2 ( 3 ) have been resolved by single crystal X-ray diffraction. The titanium oxo organo cores of these clusters are also characterized in solution by 17 O NMR spectroscopy and in solid-state by 13 C CP MAS NMR spectroscopy.

Molecular Design of Sol-Gel Derived Hybrid Organic-Inorganic Nanocomposites

Organic-inorganic hybrids appear as a creative alternative to obtain new materials with unusual features. Applications of these materials in the fields of optics, iono-electronics, mechanics, membranes, protective coatings, catalysis, sensors, biology,...are expected. This is related to their polyphasic nanostructures, leading to multifunctional materials.

Ketones as an oxolation source for the synthesis of titanium-oxo-organoclusters

Two titanium-oxo clusters, [Ti3O(OPri)7(O3C9H15)] 1 and [Ti11O13(OPri)18] 2, have been obtained through the reactions of Ti(OPri)4 with ketones such as acetone, acetylacetone and diacetone alcohol. Complex 1 is composed of a trinuclear unit that is capped by a tridentate enolate ligand synthesized insitu. Complex 2 is a more condensed titanium cluster with a spherical oxo core. The titanium-oxo-organo cores of these clusters are preserved in solution as characterized by 17O, 13C, and 1H NMR spectroscopy. The possible different reactions involved in the formation of these clusters are discussed.

On the assignment of 119Sn resonances of bis[dicarboxylatotetraorganodistannoxanes] in solution and solid state 119Sn NMR spectra

Abstract The scope and limitations of 119Sn resonance assignment strategies for structural characterizations of bis[dicarboxylatotetraorganodistannoxanes] by 2D gradient assisted 1H–119Sn HMQC NMR in solution and MAS 119Sn NMR in the solid state are discussed for three compounds, the structure of which was already known by X-ray diffraction, bis[diacetatotetramethyldistannoxane] (1), bis[bis(2,2-dimethylpropanoato)tetramethyldistannoxane] (3), bis[bis(pentafluorobenzoato)tetra-n-butyldistannoxane] (4) and for the novel compound bis[bis(4-methylbenzoato)tetramethyldistannoxane] (2), for which an X-ray crystal structure is also reported. The structures of {R′COO(R2Sn)–O–(SnR2)OOCR′}2 each feature a central R8Sn4O2 core, and in addition to the μ3-oxo links between the endo- and exo-cyclic tin atoms, the carboxylate ligands associating in a variety of structural motifs. Their relationship to 119Sn MAS NMR patterns, in particular, the principal components of the 119Sn shielding tensors, is discussed.

New synthesis of the nanobuilding block {(BuSn)12O14(OH)6}2+and exchange properties of {(BuSn)12O14(OH)6}(O3SC6H4CH3)2

Abstract This paper deals with a new and easy way to synthesize the macrocation {(BuSn) 12 O 14 (OH) 6 } 2+ from BuSnO(OH) and p -toluene sulfonic acid. It was isolated by crystallization as {(BuSn) 12 O 14 (OH) 6 }(O 3 SC 6 H 4 CH 3 ) 2 C 4 H 8 O 2 . Exchange properties of sulfonates with different anions have been studied in several solvents by using 119 Sn- and 1 H-NMR. Sulfonate anions can be exchange in isopropanol by acetate or hydroxyl groups by reaction with sodium acetate or tetramethylammonium hydroxide, respectively.

EXAFS, Raman and 31P NMR study of amorphous titanium phosphates

The reaction of phosphoric acid with titanium alkoxides for a PO4/Ti ratio ranging from 0.5 to 2 was investigated. For these compositions, amorphous precipitates are obtained. Their microstructure has been studied by means of Raman, nuclear magnetic resonance and X-ray absorption spectroscopies. The phosphatation of titanium alkoxide increases the Ti coordination number to 6 and the symmetry becomes purely octahedral for a P/Ti ratio of 2. For the composition range 0 < PO4/Ti ⩽ 2, phosphate anions are homogeneously dispersed in the precipitate and bound to titanium, the coordination of which is completed by oxo-, hydroxo- and remaining alkoxy- groups. Short TiO distances are observed in the materials having the lowest P/Ti ratios.

DI-n-BUTYL-, TRI-n-BUTYL- AND TRIPHENYLTIN STEROIDCARBOXYLATES: SYNTHESIS, NMR CHARACTERIZATION AND IN VITRO ANTITUMOUR ACTIVITY

1 Vrije Universiteit Brüssel, Pleinlaan 2, B-1050 Brussels, Belgium a Department of General and Organic Chemistry, Faculty of Applied Sciences b High Resolution NMR Centre 2 Universite Libre de Bruxelles a Service de Resonance Magnetique, CPI-232, Boulevard du Triomphe, B-1050 Brussels, Belgium b Chimie Organique Physique, Faculte des Sciences, Avenue F. D. Roosevelt, 50, B-1050 Brussels, Belgium 3 Laboratory for Tumor Biology and Pharmacology, Academic Hospital Rotterdam, P. O. Box 2040, NL-3000 CA Rotterdam, the Netherlands 4 Medical Department, Pharmachemie Β. V., Haarlem, the Netherlands 5 Laboratoire de Chimie de la Matiere Condensee, URA CNRS 1466, Tour 54, 5e etage, Universite Pierre et Marie Curie, 4 Place Jussieu, F-75252 Paris Cedex 05 France