Selective Hydrogenations and Dechlorinations in Water Mediated by Anionic Surfactant Stabilized Pd Nanoparticles

We report a facile, inexpensive and green method for the preparation of Pd nanoparticles in aqueous medium stabilized by anionic sulfonated surfactants sodium 1-dodecanesulfonate 1a, sodium dodecylbenzenesulfonate 1b, dioctyl sulfosuccinate sodium salt 1c and poly(ethylene glycol) 4-nonylphenyl-3-sulfopropyl ether potassium salt 1d simply obtained by stirring aqueous solutions of Pd(OAc)2 with the commercial anionic surfactants further treated under hydrogen atmosphere for variable times. The aqueous Pd nanoparticles solutions were tested in the selective hydrogenation reactions of aryl-alcohols, -aldehydes and -ketones leading to complete conversion to the deoxygenated products even in the absence of strong Brønsted acids in the reduction of aromatic aldehydes and ketones, in the controlled semi-hydrogenation of alkynes leading to alkenes and in the efficient hydro-dechlorination of aromatic substrates. In all cases the micellar media were crucial to stabilize the metal nanoparticles, to dissolve substrates, to steer product selectivity and to enable recycling. What is interesting is also that a benchmark catalyst like Pd/C can be often surpassed in activity and/or selectivity in the reactions tested by simply switching to the appropriate commercially available surfactant, thereby providing an easy to use, flexible and practical catalytic system capable of efficiently addressing a variety of synthetically significant hydrogenation reactions

Hydration of aromatic alkynes catalyzed by a self-assembled hexameric organic capsule

The combination of a Bronsted acid catalyst and a supramolecular organic capsule formed by the self-assembly of six resorcin[ 4] arene units efficiently promotes the mild hydration of aromatic alkynes to their corresponding ketones. The capsule provides a suitable nanoenvironment that favors protonation of the substrate and addition of water

Aqueous biphasic treatment of some nitrocompounds with hydrogen in the presence of a biogenerated Pd-polysaccharide

A strain of Klebsiella oxytoca BAS-10, known to produce a specific exopolysaccharide (EPS), when grown aerobically in static mode in the presence of Pd(NO3)(2), generated the species Pd-EPS that was used as catalyst precursor in the aqueous biphasic treatment of some nitrocompounds with hydrogen. Nitrobenzene was hydrogenated to aniline with almost quantitative yields and the catalyst, embedded in the aqueous phase, was used with success and with near the same efficiency in three recycling experiments. In the case of 1-iodo-4-nitrobenzene only nitrobenzene was obtained while the unsaturated nitro compound beta-methyl-beta-nitrostyrene afforded both the corresponding oxime and the saturated nitro derivative

Magnetic Properties of Ab initio Model for Iron-Based Superconductors LaFeAsO

By using variational Monte Carlo method, we examine an effective low-energy model for LaFeAsO derived from an ab initio downfolding scheme. We show that quantum and many-body fluctuations near a quantum critical point largely reduce the antiferromagnetic (AF) ordered moment and the model not only quantitatively reproduces the small ordered moment in LaFeAsO, but also explains the diverse dependence on LaFePO, BaFe2As2 and FeTe. We also find that LaFeAsO is under large orbital fluctuations, sandwiched by the AF Mott insulator and weakly correlated metals. The orbital fluctuations and Dirac-cone dispersion hold keys for the diverse magnetic properties.Comment: 4 pages, 4 figure

Micellar Nanoreactors

As clearly described in the series of illustrative examples reported above, the use of micellar environments in catalysis is not just a soapy version of homogeneous catalysis.71 Micelles behave much more as nanoreactors characterized by unique features with all the extra advantages intrinsic in the use of water as solvent. Micellar catalysis has been demonstrated to be suitable to almost all classes of chemical transformations, in particular for a wide range of reactions promoted by metal complexes or organometallic species, also with impressive examples in asymmetric catalysis. The great advantage of using catalysts already developed for use in organic media without the need of ligand modifications to make the catalyst compatible with water, together with the self-assembling nature of surfactants, is the key factor for the success of micellar catalysis with metal species. The surfactant is not just a spectator as usually the solvent is believed to be, rather it directs the overall system. A critical balance between catalyst, substrate, and surfactant properties must be analyzed in detail in order to ensure high yield, selectivity, and recyclability. It can be predicted that, thanks to their generally low cost, surfactants will soon find some applications in large-scale synthetic methods suitable for industrial applications

Chirality induction from a chiral guest to the hydrogen bonding network of its hexameric resorcinarene host capsule

The hexameric capsule of resorcin[4]arene 1 is capable of encapsulating tertiary amines, which has recently been used in the application of [( 1 ) 6 (H 2 O) 8 ] as (co-)catalyst in various asymmetric reactions. However, not much is known about the highly asymmetric but conformationally very dynamic structure of the capsule after uptake of chiral molecules. Therefore, in this contribution, we utilize electronic circular dichroism and vibrational circular dichroism spectroscopy to investigate how several chiral guest molecules affect the structural preferences of the capsule [( 1 ) 6 (H 2 O) 8 ]. In particular, we show that one small chiral amine encapsulated in [( 1 ) 6 (H 2 O) 8 ] is sufficient to control and dictate the stereochemical preferences of the entire capsule. Furthermore, neither strong π–π interactions nor a significant steric bulk are required for this induction. The observation of such a chiral imprint of the guest's stereochemistry onto its host molecule is expected to have implications also for other supramolecular capsules

Artificial graphene as a tunable Dirac material

Artificial honeycomb lattices offer a tunable platform to study massless Dirac quasiparticles and their topological and correlated phases. Here we review recent progress in the design and fabrication of such synthetic structures focusing on nanopatterning of two-dimensional electron gases in semiconductors, molecule-by-molecule assembly by scanning probe methods, and optical trapping of ultracold atoms in crystals of light. We also discuss photonic crystals with Dirac cone dispersion and topologically protected edge states. We emphasize how the interplay between single-particle band structure engineering and cooperative effects leads to spectacular manifestations in tunneling and optical spectroscopies.Comment: Review article, 14 pages, 5 figures, 112 Reference

Host-Catalyzed Cyclodehydration–Rearrangement Cascade Reaction of Unsaturated Tertiary Alcohols

The Brønsted acidic resorcin[4]arene hexamer can be applied as an effective catalyst in the dehydrative cyclization and subsequent rearrangement of unsaturated tertiary alcohols. This is the first report on catalyzing such a reaction with a Brønsted acid. Scope and limitations of this cyclopentene-forming reaction sequence are presented. Furthermore, substrate-selective conversion as well as competitive inhibition are described and provide evidence that the reactions proceed within the cavity of the self-assembled structure. Additionally, a cyclobutanone-forming intramolecular hydride transfer of an encapsulated cyclopropyl acetate is reported

Electronic Structure Calculation by First Principles for Strongly Correlated Electron Systems

Recent trends of ab initio studies and progress in methodologies for electronic structure calculations of strongly correlated electron systems are discussed. The interest for developing efficient methods is motivated by recent discoveries and characterizations of strongly correlated electron materials and by requirements for understanding mechanisms of intriguing phenomena beyond a single-particle picture. A three-stage scheme is developed as renormalized multi-scale solvers (RMS) utilizing the hierarchical electronic structure in the energy space. It provides us with an ab initio downfolding of the global band structure into low-energy effective models followed by low-energy solvers for the models. The RMS method is illustrated with examples of several materials. In particular, we overview cases such as dynamics of semiconductors, transition metals and its compounds including iron-based superconductors and perovskite oxides, as well as organic conductors of kappa-ET type.Comment: 44 pages including 38 figures, to appear in J. Phys. Soc. Jpn. as an invited review pape

Effect of water and lipophilic alcohols or amines on the 4-dodecylbenzenesulfonic acid-catalyzed esterifications, trans- esterifications, and amidations

4‐Dodecylbenzenesulfonic acid (DBSA) was employed in the esterification of oleic acid (OA) and the trans‐esterification of oleic oil (OO) with 1‐butanol as alcohol in the presence of various degrees of excess water. Under these conditions DBSA was found to be a highly active esterification catalyst regardless of excess water content, but was found to be a less effective for trans‐esterification reactions. Lipophilic alcohols of differing straight and branched C3‐6 chains were also tested on mixtures of OA/water (1:1) in DBSA‐catalyzed esterifications; OO/water (1:1) in trans‐esterifications; and OA/OO/water (1:1:1) in simultaneous esterifications and trans‐esterifications. While longer straight chain alcohols generally gave a two‐fold increase in yield of their corresponding alkyl oleates to 80%+, we observed a doubling from 30–50% to 60–95% of alkyl oleate yield for the OO/OA/water mixture. DBSA‐catalyzed amidations of OO and methyl oleate emulsions in water were conducted with 1‐butyl and 1‐heptyl amine where it was found that the more lipophilic the ester moiety the higher the yield of alkyl amide