Reactions of Au+ and Au− with benzene and fluorine-substituted benzenes

Reactions of gold anions and cations generated by laser desorption/ionization were studied in the FTICR spectrometer. Au⁻ associated with C₆F₆ to give the novel Au⁻(C₆F₆) complex, whose binding energy was estimated to be 24 ± 4 kcal mol⁻¹ from analysis of the radiative association (RA) kinetics. Au⁺ associated with C₆F₅H to give Au⁺(C₆F₅H), with binding energy estimated to be 31 kcal mol⁻¹. Au⁺ reacted with C₆H₆ to form the well known Au⁺(C₆H₆) and Au⁺(C₆H₆)₂ complexes. The observation of rapid charge transfer from Au⁺(C₆H₆) to C₆H₆ was interpreted as showing that benzene binds more strongly to neutral Au than to Au⁺. The neutral Au–C₆H₆ bond is accordingly concluded to be stronger than about 70 kcal mol⁻¹.     

Development and Characterization of Liposome‐Based Formulation of Amiloride Hydrochloride

Amiloride hydrochloride, a generally used diuretic recently has been found effective in the treatment of epilepsy. The side effects of the drug, such as hyperkalemia, hypertension, and hyperaldosteronism were controlled by reducing the dose and targeting the drug to the brain. The objective of this study was to determine the factors influencing encapsulation of amiloride hydrochloride in liposomes and to demonstrate the anti‐epileptic potential of liposomal drug. A series of liposomal formulations of amiloride hydrochloride were prepared by varying the compositions of the formulations. The optimized formulation consisted of 10 mg/mL of amiloride hydrochloride, L‐phosphatidyl choline, lecithin, cholesterol, and butylated hydroxy toulene. The percentage entrapment efficiency in the optimized formulation was 44%. The drug to lipids ratio and L‐phosphatidyl choline: lecithin: cholesterol: butylated hydroxy toulene ratios were 2.0:3.0 and 5:5:5:2, respectively. The formulation showed an in vitro release of 98.17% in 8 hours, and the best fit kinetic model was Peppas model. Treatment with amiloride hydrochloride liposomes resulted in a significant increase in seizure threshold as compared to free drug in increasing current electroshock seizures in mice, which indicated an increase in CNS uptake of drug in liposome formulation.     

Rational Design of Pt−Pd−Ni Trimetallic Nanocatalysts for Room-Temperature Benzaldehyde and Styrene Hydrogenation

Nanostructures of the multimetallic catalysts offer great scope for fine tuning of heterogeneous catalysis, but clear understanding of the surface chemistry and structures is important to enhance their selectivity and efficiency. Focussing on a typical Pt−Pd−Ni trimetallic system, we comparatively examined the Ni/C, Pt/Ni/C, Pd/Ni/C and Pt−Pd/Ni/C catalysts synthesized by impregnation and galvanic replacement reaction. To clarify surface chemical/structural effect, the Pt−Pd/Ni/C catalyst was thermally treated at X=200, 400 or 600 °C in a H₂ reducing atmosphere, respectively termed as Pt−Pd/Ni/C−X. The as-prepared catalysts were characterized complementarily by XRD, XPS, TEM, HRTEM, HS-LEIS and STEM-EDS elemental mapping and line-scanning. All the catalysts were comparatively evaluated for benzaldehyde and styrene hydrogenation. It is shown that the “PtPd alloy nanoclusters on Ni nanoparticles” (PtPd/Ni) and the synergistic effect of the trimetallic Pt−Pd−Ni, lead to much improved catalytic performance, compared with the mono- or bi- metallic counterparts. However, with the increase of the treatment temperature of the Pt−Pd/Ni/C, the catalytic performance was gradually degraded, which was likely due to that the favourable nanostructure of fine “PtPd/Ni” was gradually transformed to relatively large “PtPdNi alloy on Ni” (PtPdNi/Ni) particles, thus decreasing the number of noble metal (Pt and Pd) active sites on the surface of the catalyst. The optimum trimetallic structure is thus the as synthesised Pt−Pd/Ni/C. This work provides a novel strategy for the design and development of highly efficient and low-cost multimetallic catalysts, e. g. for hydrogenation reactions.     

Low-temperature sol–gel synthesis of anatase nanoparticles modified by Au, Pd and Pt and activity of TiO2/Au, Pd, Pt photocatalysts in water splitting

Base catalyzed hydrolysis and condensation of Ti isopropoxide with water at ambient temperature and molar ratio H₂O/Ti(i-PrOH)₄ varied from 1 to 100 was studied. It was found that molar ratio H₂O/Ti(i-PrOH)₄ = 100 originated amorphous TiO₂-precursor of summary composition TiO_1.9(OH)_0.2 with a specific surface area of 354 m²/g. Low-temperature crystallization of amorphous TiO₂-precursor to nanostructured anatase at 80 °C in a slightly reducing environment of d-glucose was studied. It was found that the low-temperature nucleation and crystallization of anatase was initiated (activated) by combined effects of d-glucose and Au⁰, Pd⁰ and Pt⁰ nanoparticles, generated in situ by slow reduction of Au³⁺, Pd²⁺ and Pt⁴⁺ ions using d-glucose. Considerable photocatalytic activity of Ti-hydroxide-oxide/Au, Pd, Pt catalysts prepared at low-temperature was associated with high content of nanostructured anatase and low content of Au, Pd and Pt nanoparticles (0.02 wt.%) effectively deposited on the surface of titania particles. The maximum hydrogen evolution rates 3.4 μmol/min g at Ti-hydroxide-oxide/Au, 4.0 μmol/min g at Ti-hydroxide-oxide/Pd and 4.1 μmol/min g at Ti-hydroxide-oxide/Pt were found. The activity of all TiO₂/Au, Pd and Pt catalysts increased by calcination at 600 °C from 50 to 100 %.     

Development of Catalytic Site-Selective C−H Oxidation

Direct C−H bond oxygenation is a strong and useful tool for the construction of oxygen functional groups. After Chen and White's pioneering works, various non-heme-type iron and manganese complexes were introduced, leading to strong development in this area. However, for this method to become a truly useful tool for synthetic organic chemistry, it is necessary to make further efforts to improve site-selectivity, and catalyst durability. Recently, we found that non-heme-type ruthenium complex cis- 1 presents efficient catalysis in C(sp³)−H oxygenation under acidic conditions. cis- 1 -catalysed C−H oxygenation can oxidize various substrates including highly complex natural compounds using hypervalent iodine reagents as a terminal oxidant. Moreover, the catalyst system can use almost stoichiometric water molecules as the oxygen source through reversible hydrolysis of PhI(OCOR)₂. It is a strong tool for producing isotopic-oxygen-labelled compounds. Moreover, the environmentally friendly hydrogen peroxide can be used as a terminal oxidant under acidic conditions.     

Rational Development of Remote C−H Functionalization of Biphenyl: Experimental and Computational Studies

A simple and efficient nitrile-directed meta-C−H olefination, acetoxylation, and iodination of biaryl compounds is reported. Compared to the previous approach of installing a complex U-shaped template to achieve a molecular U-turn and assemble the large-sized cyclophane transition state for the remote C−H activation, a synthetically useful phenyl nitrile functional group could also direct remote meta-C−H activation. This reaction provides a useful method for the modification of biaryl compounds because the nitrile group can be readily converted to amines, acids, amides, or other heterocycles. Notably, the remote meta-selectivity of biphenylnitriles could not be expected from previous results with a macrocyclophane nitrile template. DFT computational studies show that a ligand-containing Pd–Ag heterodimeric transition state (TS) favors the desired remote meta-selectivity. Control experiments demonstrate the directing effect of the nitrile group and exclude the possibility of non-directed meta-C−H activation. Substituted 2-pyridone ligands were found to be key in assisting the cleavage of the meta-C−H bond in the concerted metalation–deprotonation (CMD) process.     

Development of Lactose Biosensor Based on β‐Galactosidase and Glucose Oxidase Immobilized into Gelatin

In this article, we describe the preparation of a new lactose biosensor based on electrode coating with β‐galactosidase and glucose oxidase immobilized gelatin. For this purpose, β‐galactosidase and glucose oxidase enzymes were immobilized onto gelatin by crosslinking with glutaraldehyde. Properties of the immobilized β‐galactosidase and glucose oxidase enzymes electrode have been studied. The effects of glutaraldehyde concentration, temperature and pH variations and reusability were among the subjects analyzed. Lactose biosensors were subjected to continuous repeated use in order to observe reusability and shelf life; where standard lactose and milk samples were used as substrate solutions. Continuous reuse experiments showed that most of the lactose biosensors activities were retained even after the 10th use in a period of 30 days.     

Geometrical structures of trimetallic Ag–Pd–Pt and Au–Pd–Pt clusters up to 147 atoms

Structural Chemistry - The core-shell morphologies of (PdPt)coreAgshell and (PdPt)coreAushell up to 147 atoms are investigated. The structural optimization of M–Pd–Pt (M = Ag or Au) is...     

DFT studies of the characteristics of Pd−Pt core-shell clusters

It is reported that Pd?Pt core-shell type nanoclusters in which the inner atoms of the Pd cluster are substituted by Pt significantly enhance the catalytic activity for cycloocatdiene hydrogenation. In order to discuss the electronic states of core-shell clusters, DFT calculations were carried out for Pd₁₃, Pt₁₃, Pt/Pd₁₂, Pd/Pt₁₂ Pd₃₈ and Pd₆/Pt₃₂ clusters. From these calculations, it was found that the charge transfer between the core atoms and the shell atoms played an important role for the modification of the electronic state of the surface atoms in them.     

Understanding the Surprising Oxidation Chemistry of Au−OH Complexes

Au is known to be fairly redox inactive (in catalysis) and bind oxygen adducts only quite weakly. It is thus rather surprising that stable Au−OH complexes can be synthesized and used as oxidants for both one- and two-electron oxidations. A charged Au^III−OH complex has been shown to cleave C−H and O−H bonds homolytically, resulting in a one-electron reduction of the metal center. Contrasting this, a neutral Au^III−OH complex performs oxygen atom transfer to phosphines, resulting in a two-electron reduction of the hydroxide proton to form a Au^III−H rather than causing a change in oxidation state of the metal. We explore the details of these two examples and draw comparisons to the more conventional reactivity exhibited by Au^I−OH. Although the current scope of known Au−OH oxidation chemistry is still in its infancy, the current literature exemplifies the unique properties of Au chemistry and shows promise for future findings in the field.     

Direct Trifluoromethylselenolation and Fluoroalkylselenolation of C−H Bonds: Recent Advances in Reagents Development and Reactions

Due to their high lipophilicity and strong electron-withdrawing property, more and more attention has been paid to introducing trifluoromethylseleno and fluoroalkylseleno moieties into organic molecules. In this short review, we categorize the synthesis of compounds that combine selenium and fluorinated moieties into two main types: trifluoromethylselenolation (CF₃Se) and fluoroalkylselenolation (R_fSe, except CF₃Se). This review aims to provide a summary of the recent advances in direct C−H trifluoromethylselenolation and fluoroalkylselenolation from the synthesis of trifluoromethylselenolation and fluoroalkylselenolation reagents to their application. Based on the method of how the R_fSe group was introduced, the main content is divided into three parts: transition-metal-free reactions, transition-metal-mediated/catalyzed reactions and photo-catalyzed reactions. The general substrate scope, mechanism and limitations would also be discussed so that we hope the review will serve as an inspiration for further research in this appealing research field.     

Development of sterically hindered SPOs and enantioselective Ni−Al bimetallic catalyzed C−H cyclization of 4-oxoquinazolines with tethered alkenes

The Ni−Al bimetallic catalysis of intramolecular enantioselective and regioselective C−H cyclization of 4-oxoquinazolines with tethered alkenes has been successfully developed. Some new secondary phosphine oxides (SPOs) with large steric hindrance (SPO6-11) were designed and successfully synthesized from readily available chiral amines or amino acids. The developed chiral SPOs as ligands or preligands demonstrate much higher efficiency in the asymmetric catalytic reactions than the reported traditional ones. A new class of chiral tricyclic pyrroloquinazolinones were obtained in up to 95% yield and 99% ee.     

Dual Plasmonic Au−Cu2−xS Nanocomposites: Design Strategies and Photothermal Properties

Coupling two different materials to create a hybrid nanostructured system is a powerful strategy for achieving synergistically enhanced properties and advanced functionalities. In the case of Au and Cu_2−xS, their combination on the nanoscale results in dual plasmonic Au−Cu_2−xS nanocomposites that exhibit intense photon absorption in both the visible and the near-infrared spectral ranges. Their strong light-absorbing properties translate to superior photothermal transduction efficiency, making them attractive in photothermal-based applications. There are several nanostructure configurations that are possible for the Au−Cu_2−xS system, and the successful fabrication of a particular architecture often requires a carefully planned synthetic strategy. In this Minireview, the different synthetic approaches that can be employed to produce rationally designed Au−Cu_2−xS nanocomposites are presented, with a focus on the experimental protocols that can lead to heterodimer, core–shell, reverse core–shell, and yolk–shell configurations. The photothermal behavior of these materials is also discussed, providing a glimpse of their potential use as photothermally active agents in therapeutic and theranostic applications.     

Simultaneous LC−UV Analysis of Mirodenafil and Its Two Main Metabolites in Rat Plasma and Urine, and in Tissue Homogenates

A simple, rapid, and reproducible isocratic reversed-phase LC method has been established for simultaneous analysis of mirodenafil and its two main metabolites, SK3541 and SK3544, in rat plasma, urine, and tissue homogenates. Samples were deproteinized with acetonitrile containing sildenafil (internal standard). The compounds were separated on a C₁₈ column with 52:48 (v/v) 0.02 m ammonium acetate buffer (pH 6)—acetonitrile as mobile phase at a flow rate of 1.4 mL min^?1. UV detection was at 254 nm and detection limits of mirodenafil, SK3541, and SK3544 in plasma were 0.03, 0.05, and 0.1 μg mL^?1, respectively. The method is applicable to pharmacokinetic studies of mirodenafil and its metabolites in rats.     

Controlled green synthesis of Au–Pt bimetallic nanoparticles using chlorogenic acid

Research on Chemical Intermediates - Well-dispersed Au–Pt alloyed bimetallic nanoparticles are synthesized using chlorogenic acid as the only reducing agent and stabilizer to reduce Au/Pt...     

An EQCN assessment of electrocatalytic oxidation of methanol at nanostructured Au–Pt alloy nanoparticles

Alloy nanocrystals encapsulated with alkyl dithiolates (“core-shell” nanoparticles) serve as an intriguing class of nanostructured catalysts. This paper reports the preliminary results of an electrochemical quartz-crystal nanobalance (EQCN) investigation of mass transport associated with the catalytic activation and methanol oxidation at nanostructured Au–Pt nanocrystals. It is demonstrated that the catalytic activation and oxidation of methanol are accompanied by mass fluxes across the nanostructured film. The mass transport involves oxidation–reduction of surface oxygenated species, methanol adsorption and oxidation, solvent breath and product release. The implication of the EQCN results to the understanding of the core-shell nanostructured catalytic mechanism is discussed.