Yannick Guari

Water-Dispersible Sugar-Coated Iron Oxide Nanoparticles. An Evaluation of their Relaxometric and Magnetic Hyperthermia Properties

Synthesis of functionalized magnetic nanoparticles (NPs) for biomedical applications represents a current challenge. In this paper we present the synthesis and characterization of water-dispersible sugar-coated iron oxide NPs specifically designed as magnetic fluid hyperthermia heat mediators and negative contrast agents for magnetic resonance imaging. In particular, the influence of the inorganic core size was investigated. To this end, iron oxide NPs with average size in the range of 4-35 nm were prepared by thermal decomposition of molecular precursors and then coated with organic ligands bearing a phosphonate group on one side and rhamnose, mannose, or ribose moieties on the other side. In this way a strong anchorage of the organic ligand on the inorganic surface was simply realized by ligand exchange, due to covalent bonding between the Fe(3+) atom and the phosphonate group. These synthesized nanoobjects can be fully dispersed in water forming colloids that are stable over very long periods. Mannose, ribose, and rhamnose were chosen to test the versatility of the method and also because these carbohydrates, in particular rhamnose, which is a substrate of skin lectin, confer targeting properties to the nanosystems. The magnetic, hyperthermal, and relaxometric properties of all the synthesized samples were investigated. Iron oxide NPs of ca. 16-18 nm were found to represent an efficient bifunctional targeting system for theranostic applications, as they have very good transverse relaxivity (three times larger than the best currently available commercial products) and large heat release upon application of radio frequency (RF) electromagnetic radiation with amplitude and frequency close to the human tolerance limit. The results have been rationalized on the basis of the magnetic properties of the investigated samples.

Towards the Ultimate Size Limit of the Memory Effect in Spin‐Crossover Solids

Although the originof the spin-crossover phenomenon is purely molecular, themacroscopic behavior of these systems in the solid state isstrongly influenced by short- and long-range interactions (ofmainly elastic origin) between the transition-metal ions,giving rise to remarkable cooperative phenomena, such asfirst-order phase transitions.

Catalytic Formation of Carbon–Carbon Bonds by Activation of Carbon–Hydrogen Bonds

The direct functionalization of C–H bonds by formation of a C–C bond is an interesting and important alternative to coupling reactions involving halide derivatives. These reactions are complex but during the past few years a number of new systems have been developed which display promising scope. This microreview will briefly mention the different mechanisms leading to C–H activation and describe the new systems leading to the catalytic formation of carbon–carbon bonds.

Luminescent and Magnetic Cyano-Bridged Coordination Polymers Containing 4d-4f Ions: Toward Multifunctional Materials

A new family of cyano-bridged coordination polymers Ln(H(2)O)(5)[M(CN)(8)] (Ln = Eu, Tb, Sm, Gd; M = Mo, W) were obtained and characterized by X-ray diffraction, photoluminescence spectroscopy, and magnetic analyses. These compounds are isomorphous and crystallize in the tetragonal system P4/nmm, forming two-dimensional gridlike networks. The Eu- and Tb-containing coordination polymers are room-temperature optically active emitters displaying the characteristic (5)D(0) --> (7)F(0-4) (Eu(3+)) and (5)D(4) --> (7)F(6-2) (Tb(3+)) transitions. All of the coordination polymers except Eu(H(2)O)(5)[M(CN)(8)] present long-range magnetic ordering at low temperatures. The coexistence of luminescence with ferromagnetic ordering for Tb(H(2)O)(5)[M(CN)(8)] (M = Mo, W) suggests that these compounds may be considered as bifunctional magneto-luminescent coordination polymers exhibiting diverse physical responses when subjected to various external stimuli.

A Luminescent and magnetic cyano-bridged Tb3+-Mo5+ coordination polymer: toward multifunctional materials.

A new cyano-bridged coordination polymer network Tb(H2O)5-[Mo(CN)8] was obtained and characterized. This compound has a two-dimensional layered structure and presents luminescence along with a magnetic transition at low temperature.

Extraction of radioactive cesium using innovative functionalized porous materials

A new approach to an efficient and selective extraction of Cs+ ions from water, sea water enriched with Cs+ and a radioactive solution simulating the effluents of the Fukushima reactors (137Cs, 29 kBq L−1) was developed by using porous silica- or glass-based nanocomposites containing Prussian blue type nanoparticles, Co2+/[Fe(CN)6]3−, with sizes below 10 nm. A particular emphasis is given on the kinetics of cesium sorption fitted by using the classical reaction order model as well as a diffusion model in order to better understand the sorption mechanism. Compared to the amount of Co2+/[Fe(CN)6]3− nanoparticles, the sorption capacities of studied nanocomposites are more than three times higher than the ones observed for the respective bulk materials. These nanocomposites present a high selectivity to Cs+ and extract it in trace amounts.

A High‐Temperature Molecular Ferroelectric Zn/Dy Complex Exhibiting Single‐Ion‐Magnet Behavior and Lanthanide Luminescence

Multifunctional molecular ferroelectrics are exciting materials synthesized using molecular chemistry concepts, which may combine a spontaneous electrical polarization, switched upon applying an electric field, with another physical property. A high-temperature ferroelectric material is presented that is based on a chiral Zn(2+) /Dy(3+) complex exhibiting Dy(3+) luminescence, optical activity, and magnetism. We investigate the correlations between the electric polarization and the crystal structure as well as between the low-temperature magnetic slow relaxation and the optical properties.

AN EFFICIENT, PALLADIUM-CATALYSED, AMINATION OF ARYL BROMIDES

Aryl bromides are coupled to primary aliphatic amines, anilines and cyclic secondary amines in an efficient and selective procedure using catalytic amounts of Pd(OAc)2 and the chelating ligand 9,9-dimethyl-4,6-bis(diphenylphosphino)xanthene (Xantphos). This catalyst system accomodating low catalyst loadings (0.5 mol % Pd) allows amination of both electron-poor and electron-rich aryl bromides. Even sterically crowded substrates show good reactivity.

Cooperative spin crossover phenomena in [Fe(NH2trz)3](tosylate)2 nanoparticles

Nanoparticles of the [Fe(NH(2)trz)(3)](tosylate)(2) spin crossover complex of 3-4 nm size were synthesized and dispersed in a nonionic surfactant. This colloidal system exhibits thermal spin crossover phenomena associated with a virtually first order transition. By thermal treatment the colloidal suspension can be transformed into a fibrous structure forming a gel.

Synthesis and behaviour of size controlled cyano-bridged coordination polymer nanoparticles within hybrid mesoporous silica

Size controlled cyano-bridged coordination polymer nanoparticles Mn+/[M′(CN)m]3− (where Mn+ = Ni2+, Fe2+, Co2+ and M′ = Fe3+, Co3+(m = 6); Mo5+ (m = 8)) have been synthesised and organised by using mesostructured hybrid silica hosts of various sizes (3.4, 5.3 and 7.5 nm) containing –(CH2)2C5H4N groups. The obtained composite materials were studied by transmission electronic microscopy (TEM), infrared and electronic spectroscopies, nitrogen sorption, X-ray diffraction and magnetic measurements. These analyses reveal the formation of hetero- or homo-metallic cyano-bridged nanoparticles with controlled stoichiometry uniform in size and shape within the silica matrix. The size of the nanoparticles is controlled by the pore size of the silica used. The magnetic study of these nanocomposite materials reveal an appearance of a spin-glass like regime which can be caused by a spin frustration on the surface of the nanoparticles and/or by interparticle magnetostatic interactions.