Enhancement of the Catalytic Activity of Double Metal Cyanides for the Oxidation of Styrene by the Presence of Included Alcohols.

In recent years, people have focused on the development of simple and efficient heterogeneous catalysts for the styrene epoxidation reaction. In this work, a FeCo double metal cyanide (DMC) was modified with C1 to C6 linear alcohols, and the prepared materials were used to catalyze the reaction of styrene epoxidation in various solvents. It is noteworthy that the styrene conversion is mainly affected by modification with alcohols, while the selectivity in styrene oxide (SO) is obviously influenced by the solvent. FeCo DMC along with MeOH exhibits the best catalytic performance, with a conversion rate of 96% and a SO selectivity of 86%, in N,N-dimethylformamide (DMF) solvent. Various physical and chemical methods were used to analyze the structures and compositions of the materials. To clarify the mechanism of the improvement, we set up an original approach to investigate the kinetics of the adsorption process between the oxidant and the catalyst, using isothermal titration calorimetry (ITC). The obtained results illustrate that the adsorption process of the oxidant on the surface of FeCo DMC can be dramatically promoted by the presence of MeOH. Such a difference in adsorption thus explains the significant improvement of its catalytic activity by modification with MeOH. This study thus provides a new fundamental understanding of DMC catalysts for the styrene epoxidation reaction.

Organometallic Synthesis of Bimetallic Cobalt-Rhodium Nanoparticles in Supported Ionic Liquid Phases (Cox Rh100- x @SILP) as Catalysts for the Selective Hydrogenation of Multifunctional Aromatic Substrates.

The synthesis, characterization, and catalytic properties of bimetallic cobalt-rhodium nanoparticles of defined Co:Rh ratios immobilized in an imidazolium-based supported ionic liquid phase (Cox Rh100- x @SILP) are described. Following an organometallic approach, precise control of the Co:Rh ratios is accomplished. Electron microscopy and X-ray absorption spectroscopy confirm the formation of small, well-dispersed, and homogeneously alloyed zero-valent bimetallic nanoparticles in all investigated materials. Benzylideneacetone and various bicyclic heteroaromatics are used as chemical probes to investigate the hydrogenation performances of the Cox Rh100- x @SILP materials. The Co:Rh ratio of the nanoparticles is found to have a critical influence on observed activity and selectivity, with clear synergistic effects arising from the combination of the noble metal and its 3d congener. In particular, the ability of Cox Rh100- x @SILP catalysts to hydrogenate 6-membered aromatic rings is found to experience a remarkable sharp switch in a narrow composition range between Co25 Rh75 (full ring hydrogenation) and Co30 Rh70 (no ring hydrogenation).

Hydrogen Isotope Exchange Catalyzed by Ru Nanocatalysts: Labelling of Complex Molecules Containing N-Heterocycles and Reaction Mechanism Insights.

Ruthenium nanocatalysis can provide effective deuteration and tritiation of oxazole, imidazole, triazole and carbazole substructures in complex molecules using D2 or T2 gas as isotopic sources. Depending on the substructure considered, this approach does not only represent a significant step forward in practice, with notably higher isotope uptakes, a broader substrate scope and a higher solvent applicability compared to existing procedures, but also the unique way to label important heterocycles using hydrogen isotope exchange. In terms of applications, the high incorporation of deuterium atoms, allows the synthesis of internal standards for LC-MS quantification. Moreover, the efficacy of the catalyst permits, even under subatmospheric pressure of T2 gas, the preparation of complex radiolabeled drugs owning high molar activities. From a fundamental point of view, a detailed DFT-based mechanistic study identifying undisclosed key intermediates, allowed a deeper understanding of C-H (and N-H) activation processes occurring at the surface of metallic nanoclusters.

NHC-Stabilized Iridium Nanoparticles as Catalysts in Hydrogen Isotope Exchange Reactions of Anilines.

The preparation of N-heterocyclic carbene-stabilized iridium nanoparticles and their application in hydrogen isotope exchange reactions is reported. These air-stable and easy-to-handle iridium nanoparticles showed a unique catalytic activity, allowing selective and efficient hydrogen isotope incorporation on anilines using D2 or T2 as isotopic source. The usefulness of this transformation has been demonstrated by the deuterium and tritium labeling of diverse complex pharmaceuticals.

Tuning the Reactivity of a Heterogeneous Catalyst using N-Heterocyclic Carbene Ligands for C-H Activation Reactions.

We report the dramatic impact of the addition of N-heterocyclic carbenes (NHCs) on the reactivity and selectivity of heterogeneous Ru catalysts in the context of C-H activation reactions. Using a simple and robust method, we prepared a series of new air-stable catalysts starting from commercially available Ru on carbon (Ru/C) and differently substituted NHCs. Associated with C-H deuteration processes, depending on Ru/C-NHC ratios, the chemical outcome can be controlled to a large extent. Indeed, tuning the reactivity of the Ru catalyst with NHC enabled: 1) increased chemoselectivity and the regioselectivity for the deuteration of alcohols in organic media; 2) the synthesis of fragile pharmaceutically relevant deuterated heterocycles (azine, purine) that are otherwise completely reduced using unmodified commercial catalysts; 3) the discovery of a novel reactivity for such heterogeneous Ru catalysts, namely the selective C-1 deuteration of aldehydes.

Multiple Site Hydrogen Isotope Labelling of Pharmaceuticals.

Radiolabelling is fundamental in drug discovery and development as it is mandatory for preclinical ADME studies and late-stage human clinical trials. Herein, a general, effective, and easy to implement method for the multiple site incorporation of deuterium and tritium atoms using the commercially available and air-stable iridium precatalyst [Ir(COD)(OMe)]2 is described. A large scope of pharmaceutically relevant substructures can be labelled using this method including pyridine, pyrazine, indole, carbazole, aniline, oxa-/thia-zoles, thiophene, but also electron-rich phenyl groups. The high functional group tolerance of the reaction is highlighted by the labelling of a wide range of complex pharmaceuticals, containing notably halogen or sulfur atoms and nitrile groups. The multiple site hydrogen isotope incorporation has been explained by the in situ formation of complementary catalytically active species: monometallic iridium complexes and iridium nanoparticles.

Efficient Access to Deuterated and Tritiated Nucleobase Pharmaceuticals and Oligonucleotides using Hydrogen-Isotope Exchange.

A general approach for the efficient hydrogen-isotope exchange of nucleobase derivatives is described. Catalyzed by ruthenium nanoparticles, using mild reaction conditions, and involving either D2 or T2 as isotopic sources, this reaction possesses a wide substrate scope and a high solvent tolerability. This novel method facilitates the access to essential diagnostic tools in drug discovery and development: tritiated pharmaceuticals with high specific activities and deuterated oligonucleotides suitable for use as internal standards during LC-MS quantification.

Bimetallic Nanoparticles in Supported Ionic Liquid Phases as Multifunctional Catalysts for the Selective Hydrodeoxygenation of Aromatic Substrates.

Bimetallic iron-ruthenium nanoparticles embedded in an acidic supported ionic liquid phase (FeRu@SILP+IL-SO3 H) act as multifunctional catalysts for the selective hydrodeoxygenation of carbonyl groups in aromatic substrates. The catalyst material is assembled systematically from molecular components to combine the acid and metal sites that allow hydrogenolysis of the C=O bonds without hydrogenation of the aromatic ring. The resulting materials possess high activity and stability for the catalytic hydrodeoxygenation of C=O groups to CH2 units in a variety of substituted aromatic ketones and, hence, provide an effective and benign alternative to traditional Clemmensen and Wolff-Kishner reductions, which require stoichiometric reagents. The molecular design of the FeRu@SILP+IL-SO3 H materials opens a general approach to multifunctional catalytic systems (MM'@SILP+IL-func).

Synthesis of Water-Soluble Palladium Nanoparticles Stabilized by Sulfonated N-Heterocyclic Carbenes.

A strategy involving the decomposition of palladium(II) organometallic complexes with sulfonated N-heterocyclic carbene ligands leads to the formation of stable and water-soluble Pd nanoparticles. Three different methodologies (thermal decomposition, reduction under 13 CO atmosphere, and reduction with H2 ) gave particles with different shapes and sizes, ranging from 1.5 to 7 nm. The structures of the organometallic intermediates and organic decomposition products were elucidated by NMR spectroscopy. To check the accessibility of the surface, the nanoparticles were tested as catalysts for the chemoselective hydrogenation of styrene in water. An effect of the particle size on the catalyst activity was observed. The aqueous phase was recycled up to ten times without any precipitation of metallic palladium.

Noncontact orientation of objects in three-dimensional space using magnetic levitation.

This paper describes several noncontact methods of orienting objects in 3D space using Magnetic Levitation (MagLev). The methods use two permanent magnets arranged coaxially with like poles facing and a container containing a paramagnetic liquid in which the objects are suspended. Absent external forcing, objects levitating in the device adopt predictable static orientations; the orientation depends on the shape and distribution of mass within the objects. The orientation of objects of uniform density in the MagLev device shows a sharp geometry-dependent transition: an analytical theory rationalizes this transition and predicts the orientation of objects in the MagLev device. Manipulation of the orientation of the levitating objects in space is achieved in two ways: (i) by rotating and/or translating the MagLev device while the objects are suspended in the paramagnetic solution between the magnets; (ii) by moving a small external magnet close to the levitating objects while keeping the device stationary. Unlike mechanical agitation or robotic selection, orienting using MagLev is possible for objects having a range of different physical characteristics (e.g., different shapes, sizes, and mechanical properties from hard polymers to gels and fluids). MagLev thus has the potential to be useful for sorting and positioning components in 3D space, orienting objects for assembly, constructing noncontact devices, and assembling objects composed of soft materials such as hydrogels, elastomers, and jammed granular media.

Knight Shift in 13 C†NMR Resonances Confirms the Coordination of N-Heterocyclic Carbene Ligands to Water-Soluble Palladium Nanoparticles.

The coordination of N-heterocyclic carbene (NHC) ligands to the surface of 3.7 nm palladium nanoparticles (PdNPs) can be unambiguously established by observation of Knight shift (KS) in the 13 C resonance of the carbenic carbon. In order to validate this coordination, PdNPs with sizes ranging from 1.3 to 4.8 nm were prepared by thermal decomposition or reduction with CO of a dimethyl NHC PdII complex. NMR studies after 13 CO adsorption established that the KS shifts the 13 C resonances of the chemisorbed molecules several hundreds of ppm to high frequencies only when the particle exceeds a critical size of around 2 nm. Finally, the resonance of a carbenic carbon is reported to be Knight-shifted to 600 ppm for 13 C-labelled NHCs bound to PdNPs of 3.7 nm. The observation of these very broad KS resonances was facilitated by using Car-Purcell-Meiboom-Gill (CPMG) echo train acquisition NMR experiments.

Exploiting non-equilibrium phase separation for self-assembly.

Demixing can occur in systems of two or more particle species that experience different driving forces, e.g., mixtures of self-propelled active particles or of oppositely charged colloids subject to an electric field. Here we show with macroscopic experiments and computer simulations that the forces underlying such non-equilibrium segregation can be used to control the self-assembly of particles that lack attractive interactions. We demonstrate that, depending on the direction, amplitude and frequency of a periodic external force acting on one particle species, the structures formed by a second, undriven species can range from compact clusters to elongated, string-like patterns.

Light induced modulation of charge transport phenomena across the bistability region in [Fe(Htrz)2(trz)](BF4) spin crossover micro-rods.

We studied the effect of light irradiation on the electrical conductance of micro-rods of the spin crossover [Fe(Htrz)2(trz)](BF4) network, organized between interdigitated gold electrodes. By irradiating the sample with different wavelengths (between 295 and 655 nm) either in air or under a nitrogen atmosphere we observed both a reversible and an irreversible change of the current flowing in the device. The reversible process consists of an abrupt decrease of the current intensity (ca. 10-50%) upon light irradiation, while the irreversible process is characterized by a slow, but continuous increase in time of the current, which persists also in the dark. These photo-induced processes were only detected in the high conductance low-spin (LS) state of the complex. On switching the rods to the high spin (HS) state the conductance decreases two orders of magnitude (at the same temperature) and - as a consequence - the photo-effect vanishes.

Highly stable water-soluble platinum nanoparticles stabilized by hydrophilic N-heterocyclic carbenes.

Controlling the synthesis of stable metal nanoparticles in water is a current challenge in nanochemistry. The strategy presented herein uses sulfonated N-heterocyclic carbene (NHC) ligands to stabilize platinum nanoparticles (PtNPs) in water, under air, for an indefinite time period. The particles were prepared by thermal decomposition of a preformed molecular Pt complex containing the NHC ligand and were then purified by dialysis and characterized by TEM, high-resolution TEM, and spectroscopic techniques. Solid-state NMR studies showed coordination of the carbene ligands to the nanoparticle surface and allowed the determination of a (13)C-(195)Pt coupling constant for the first time in a nanosystem (940 Hz). Additionally, in one case a novel structure was formed in which platinum(II) NHC complexes form a second coordination sphere around the nanoparticle.

Re-appearance of cooperativity in ultra-small spin-crossover [Fe(pz){Ni(CN)4}] nanoparticles.

A reverse nanoemulsion technique was used for the elaboration of [Fe(pz){Ni(CN)4}] nanoparticles. Low-temperature micellar exchange made it possible to elaborate ultra-small nanoparticles with sizes down to 2 nm. When decreasing the size of the particles from 110 to 12 nm the spin transition shifts to lower temperatures, becomes gradual, and the hysteresis shrinks. On the other hand, a re-opening of the hysteresis was observed for smaller (2 nm) particles. A detailed (57)Fe Mössbauer spectroscopy analysis was used to correlate this unusual phenomenon to the modification of the stiffness of the nanoparticles thanks to the determination of their Debye temperature.

Water-soluble NHC Pd/Ni bimetallic nanoparticles for H/D exchange in aromatic amino-acids.

Labelling of amino-acids is important for the production of deuterated proteins. However, aromatic amino-acid reduction is a common undesired process with noble-metal nanocatalysts. In this work, we describe a new NHC-stabilized water-soluble Pd/Ni system able to perform H/D exchange reactions in an enantiospecific fashion without reducing the aromatic ring of phenylalanine and tyrosine thanks to a synergetic Pd-Ni effect.

Induction heating: an efficient methodology for the synthesis of functional core-shell nanoparticles.

Induction heating has been applied for a variety of purposes over the years, including hyperthermia-induced cell death, industrial manufacturing, and heterogeneous catalysis. However, its potential in materials synthesis has not been extensively studied. Herein, we have demonstrated magnetic induction heating-assisted synthesis of core-shell nanoparticles starting from a magnetic core. The induction heating approach allows an easy synthesis of FeNi3@Mo and Fe2.2C@Mo nanoparticles containing a significantly higher amount of molybdenum on the surface than similar materials synthesized using conventional heating. Exhaustive electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy characterization data are presented to establish the core-shell structures. Furthermore, the molybdenum shell was transformed into the Mo2C phase, and the catalytic activity of the resulting nanoparticles tested for the propane dry reforming reaction under induction heating. Lastly, the beneficial role of induction heating-mediated synthesis was extended toward the preparation of the FeNi3@WOx core-shell nanoparticles.

Magnetically Induced CO2 Methanation In Continuous Flow Over Supported Nickel Catalysts with Improved Energy Efficiency.

A new selective and efficient catalytic system for magnetically induced catalytic CO2 methanation was developed, composed of an abundant iron-based heating agent, namely a commercial iron wool, combined with supported Nickel nanoparticles (Ni NPs) as catalysts. The effect of metal oxide support was evaluated by preparing different 10 wt % Ni catalyst (TiO2 , ZrO2 , CeO2 , and CeZrO2 ) via organometallic decomposition route. As-prepared catalysts were thoroughly characterized using powder X-ray diffraction, electron microscopy, elemental analysis, vibrating sample magnetometer, and X-ray photoelectron spectroscopy techniques. High conversion and selectivity toward methane were observed at mid-temperature range, hence improving energy efficiency of the process with respect to the previous results under magnetic heating conditions. To gain further insight into the catalytic system, the effects of the synthesis method and of 0.5 wt % Ru doping were evaluated. Finally, the dynamic nature of magnetically induced heating was demonstrated through fast stop-and-go experiments, proving the suitability of this technology for the storage of intermittent renewable energy through P2G process.

Analog modeling of Worm-Like Chain molecules using macroscopic beads-on-a-string.

This paper describes an empirical model of polymer dynamics, based on the agitation of millimeter-sized polymeric beads. Although the interactions between the particles in the macroscopic model and those between the monomers of molecular-scale polymers are fundamentally different, both systems follow the Worm-Like Chain theory.

Single molecule magnet behavior of a pentanuclear Mn-based metallacrown complex: solid state and solution magnetic studies.

The magnetic behavior of the pentanuclear complex of formula Mn(II)(O(2)CCH(3))(2)[12-MC(Mn(III)(N)shi)-4](DMF)(6), 1, was investigated using magnetization and magnetic susceptibility measurements both in the solid state and in solution. Complex 1 has a nearly planar structure, made of a central Mn(II) ion surrounded by four peripheral Mn(III) ions. Solid state variable-field dc magnetic susceptibility experiments demonstrate that 1 possesses a low value for the total spin in the ground state; fitting appropriate expressions to the data results in antiferromangetic coupling both between the peripheral Mn(III) ions (J = -6.3 cm(-1)) and between the central Mn(II) ion and the Mn(III) ones (J' = -4.2 cm(-1)). In order to obtain a reasonable fit, a relatively large single ion magnetic anisotropy (D) value of 1 cm(-1) was necessary for the central Mn(II) ion. The single crystal magnetization measurements using a microsquid array display a very slight opening of the hysteresis loop but only at a very low temperature (0.04 K), which is in line with the ac susceptibility data where a slow relaxation of the magnetization occurs just around 2 K. In frozen solution, complex 1 displays a frequency dependent ac magnetic susceptibility signal with an energy barrier to magnetization reorientation (E) and relaxation time at an infinite temperature (τ(o)) of 14.7 cm(-1) and 1.4 × 10(-7) s, respectively, demonstrating the single molecule magnetic behavior in solution.