Rocío Redón

Allyl–palladium compounds with fluorinated benzenethiolate ligands. X-ray crystal structure of [(η3-C3H5)Pd(μ-SC6H4F-4)2Pd(η3-C3H5)]

Abstract Treatment of the di-μ-chloride allyl–palladium complex [(η3-C3H5)Pd(μ-Cl)2Pd(η3-C3H5)] with Pb(SR)2 in acetone affords dinuclear fluorothiolate bridged complexes of the type [(η3-C3H5)Pd(μ-SR)2Pd(η3-C3H5)] (R=C6F5, 1; C6HF4-4, 2; C6H4F-2, 3; C6H4F-3, 4 and C6H4F-4, 5). Complex 1 reacts with para-substituted phosphines P(C6H4X-4)3 to give the mononuclear perfluorobenzenethiolate complexes [Pd(SC6F5)(η3-C3H5)(P(C6H4X-4)3)] (X=F, 6; CF3, 7; OCH3, 8 and CH3, 9). The single crystal X-ray diffraction structure of [(η3-C3H5)Pd(μ-SC6H4F-4)2Pd(η3-C3H5)] (5) has been resolved.

Allyl–palladium complexes with fluorinated benzene thiolate ligands. Examination of the electronic effects in the Pd-catalyzed allylic alkylation reaction with the catalytic system [(η3-C3H5)Pd(μ-SRf)]2/PR3

Abstract The bimetallic complexes [(η 3 -C 3 H 5 )Pd(μ-SR f )] 2 [R f =C 6 F 5 , ( 1 ); C 6 F 4 H-4, ( 2 ); C 6 H 4 F-2, ( 3 ); C 6 H 4 F-3, ( 4 ) and C 6 H 4 F-4, ( 5 )] in the presence of para -substituted phosphines P(C 6 H 4 X-4) 3 [X=OCH 3 , CH 3 , H, F, Cl, and CF 3 ] are efficient catalytic systems in the allylic alkylation couplings of ( E )-3-acetoxy-1,3-diphenyl-1-propene and dimethyl malonate. Results concerning the electronic effects of both sulfur and phosphorus substituents in this reaction are discussed.

Synthesis of neutral rhenium(V) complexes with fluorinated benzenethiols: the crystal and molecular structure of [ReO(C6H4S-2-F)3(PPh3)]

Abstract The complexes [ReO(SRf)3(PPh3)] and [ReN(SRf)2(PPh3)2] [Rf=C6F5 (1) and (6), C6F4-4-H (2) and (7), C6H4-2-F (3) and (8), C6H4-3-F (4) and (9) and C6H4-4-F (5) and (10)] were synthesized in good yields by reacting [ReOCl3(PPh3)2] or [ReNCl2(PPh3)2] and the lead salt of the corresponding fluorobenzenethiol [Pb(SRf)2]. In contrast, when the free thiol HSC6F5 was employed in the presence of NEt3 as base, the ionic species [ReO(SC6F5)4][NEt3·HCl] (11) was isolated. The X-ray crystal structure of 3 was determined.

Miktoarm Star Polymer Based Multifunctional Traceable Nanocarriers for Efficient Delivery of Poorly Water Soluble Pharmacological Agents

A versatile methodology to develop an inherently fluorescent and thus traceable multifunctional nanodelivery platform based on miktoarm polymers is reported. Miktoarm stars containing covalently linked tetraiodofluorescein dye, polyethylene glycol, and polycaprolactone self-assemble into micelles, and integrate multiple functions including fluorescent tags for imaging, a hydrophobic core for drug incorporation, and a hydrophilic corona for micelle stabilization. Curcumin, a pleiotropic but very poorly water-soluble drug, is loaded into these micelles with an efficiency of 25-60 wt%. It leads to a 25 000-fold increase in its aqueous solubility, and a sustained release over a period of 7 d. These micelles are rapidly internalized into murine J774A.1 macrophages, and accumulated into discrete cellular compartments, whereas the free and physically encapsulated dye is diffused in the cytoplasm. Curcumin-loaded micelles reduce lipopolysaccharide-induced nitric oxide release. The studies establish miktoarm star based nanocarriers as highly efficient in tracking their fate and expanding the scope of pharmacological agents with limited utility in experimental medicine.

X-ray structural and dynamic behaviour study of allyl palladium compounds with fluorinated benzenethiolate bridges

Abstract In solution, allyl palladium homobimetallic complexes bridged by fluorinated benzenethiolates, [{Pd(μ-SR)(η3-C3H5)}2] where R=C6F5, 1; C6HF4-4, 2; C6H4F-2, 3; C6H4F-3, 4 and C6H4F-4, 5, are found as a mixture of syn/anti and cis/trans isomers. The variable temperature 1H and 19F NMR study of these compounds show that the four isomers undergo interconversion through two probable mechanisms, allyl rotation assisted by the solvent and inversion of the configuration at the sulphur atoms. The X-ray crystal structure determination of [{Pd(μ-SC6F5)(η3-C3H5)}2] and [{Pd(μ-S C6HF4-4)(η3-C3H5)}2] shown both complexes to be bimetallic with the metal centres found in a slightly distorted square planar environments.

Accelerated synthesis of large generation triazine dendrimers using microwave assisted reactions: a 24 hour challenge

The expedited synthesis of odd generation triazine dendrimers up to generation 9 can be executed in high yields using microwave irradiation. The efforts commence from commercially-available and inexpensive materials. Execution is facilitated by automated chromatography.

Leaching in Metal Nanoparticle Catalysis

Since the discovery of catalysis, the identification of the different species in the mechanism involved in the reaction has been a challenge. When nanocatalysis entered the scene, the detection of material that came out from solutions attracted the attention and raised several questions: was this solid part of the nanocatalyst? was it the precursor of the nanocatalysts (the so-called precatalyst)? or was it the nanocatalyst itself? The discussion focuses on whether the catalysis is determined by the species that exist in solution or if it is generated from the support and hence the catalytic reaction is carried out with these soluble species. Furthermore, it appears that leaching is a phenomenon which occurs mainly in palladium- catalyzed reactions and that involves palladium nanoparticles (NPs). The research, findings and patents in the leaching process in catalytic reactions are reviewed in the present paper.

Thermoregulated Coacervation, Metal-Encapsulation and Nanoparticle Synthesis in Novel Triazine Dendrimers

The synthesis and solubility behaviors of four generation five (G5) triazine dendrimers are studied. While the underivatized cationic dendrimer is soluble in water, the acetylated and propanoylated derivatives undergo coacervation in water upon increasing temperature. Occurring around room temperature, this behavior is related to a liquid-liquid phase transition with a lower critical solution temperature (LCST) and is explained by differences in composition, notably, the hydrophobic nature of the terminal groups. Interestingly, the water solubility of the acetylated dendrimer is affected by the addition of selected metal ions. Titrating solutions of acetylated dendrimer at temperatures below the LCST with gold or palladium ions promoted precipitation, but platinum, iridium, and copper did not. Gold nanoparticles having diameters of 2.5 ± 0.8 nm can be obtained from solutions of the acetylated dendrimer at concentrations of gold less than that required to induce precipitation by treating the solution with sodium borohydride.

Solventless synthesis of Ru(0) composites stabilized with polyphosphorhydrazone (PPH) dendrons and their use in catalysis

Ruthenium nanoparticles (NPs) are prepared by milling under air ruthenium chloride (RuCl3), sodium borohydride (NaBH4) and a polyphosphorhydrazone (PPH) dendron (generation 0 to 2) having an alkyl chain at the focal point and triarylphosphines on the surface. The resulting NPs have a diameter in the 2 to 3 nm range and they are stable upon storage in solution or as powders. They can efficiently catalyze hydrogenation of styrene. The interaction between the dendrons and the NPs is studied, and the influence of the alkyl chain length and dendron generation is also discussed.

CuO nanoparticles with PAMAM dendrimers

Abstract An easy pathway to synthesize a variety of cupric oxide (CuO) nanoshapes by a one-step wet chemical method is reported. CuO nanoparticles and nanorods were obtained from CuCl2 in a mixture of water and DMSO in the absence of a base at room temperature. 1-D CuO nanostructures resembling wires inside tubes, or nanopea pods, were shaped when polyamidoamine (PAMAM) dendrimers of generation 2 (16-NH2 end groups) or 2.5 (32-COO− end groups) were added to the CuO colloids. The evolution in time of the different nanostructures was followed by UV–visible spectroscopy. The XRD patterns, Raman spectroscopy and high-resolution transmission electron microscopy show clear evidence that all nanoshapes obtained in this work are composed by CuO. This method is a simple, versatile, and economical alternative for the fabrication of CuO nanostructures and might provide a practical reference for the controlled synthesis of other nanoarchitectures.