Dry Inert Atmosphere Research Articles

Cu-catalyzed, ligand free syntheses of arylaminopyrimidines in aqueous solution and insilico investigation of their druglikeliness properties

A ligand free Cu(NO3)2·3H2O catalyzed synthetic protocol for arylaminopyrimidines starting from chloropyrimidines and aliphatic/aromatic amines in aqueous medium is being reported here. The procedure is quite general and was successful to deliver 22 numbers of arylaminopyrimidines including 5 novel compounds in good to excellent yield (54–97 %). The reaction protocol doesn't require dry solvents and inert atmosphere, and in comparison to existing reports, it worked under mild reaction temperature (80 °C). The developed methodology offers first application of ligand free Ullmann type coupling reactions for the synthesis of arylaminopyrimidine-2,4(1H,3H)-diones and arylaminopyrimidines. The aqueous medium containing the catalyst system can be reusable up to third run without significant decline in productivity. All the 22 synthesized compounds were computed to investigate their druglikeliness properties using SwissADME tool. 18 of those were found to obey all the criteria set for druglikeliness properties and 5 of those fulfilling completely the requirements of all the six parameters of bioavailability radar viz. lipophilicity, molecular weight, polarity, solubility, flexibility and saturation to be orally bioavailable. While all the compounds were predicted to have high gastrointestinal (GI) absorption, 16 of those have blood brain barrier (BBB) penetration ability.

Molecular and silica-supported metal complexes as new catalysts for hydrosilylation

Two disiloxanes with pyridyl or isocyanide functional groups, as well as silica materials carrying pyridyl or thiol functionalities were used as ligands for Pt(IV) and Fe(III) ions. The molecular and silica-supported metal complexes were tested in a model hydrosilylation reaction between 1,3-divinyl tetramethyldisiloxane and 1,1,3,3-tetramethyldisiloxane, conducted in (pseudo)-heterogeneous conditions. The new hydrosilylation catalysts afforded 75-100 % conversion and 87-93 % selectivity, based on NMR data, while some of them presented recyclability; they were also successful in silicones crosslinking at room temperature. In particular, the iron-isocyanide disiloxane complex is proposed as a promising, cheap, unsophisticated and stable catalyst, capable to act in heterogeneous conditions, without the need of dry solvent or inert atmosphere. Silica-supported Pt or Pt/Pd catalysts, obtained with commercial or recovered noble metals precursors, presented high conversion and increased regioselectivity in the hydrosilylation reaction, being reusable, and are efficient in other hydrosilylation reactions, useful in organic and silicon chemistry.

Synthesis and Thermal Stability of Manganese(III) Acetylacetonate

The dependence of the stability of Mn(C5H7O2)3 modifications on the properties of the solvent chosen for recrystallization is considered. Low-polarity solvents with a low dielectric permittivity enhance intermolecular interactions, which leads to the formation of the β-Mn(C5H7O2)3 modification during the synthesis of Mn(C5H7O2)3 from chloroform solutions. The use of mixtures of chloroform with petroleum ether makes it possible to control supersaturation, the rate of formation, and growth of phase nuclei due to the evaporation of chloroform under isothermal conditions. The use of polar solvents for recrystallization favors the formation of γ-Mn(C5H7O2)3. The composition of the thermal decomposition products of β‑Mn(C5H7O2)3 in a dry inert atmosphere has been determined by X-ray powder diffraction, IR spectroscopy, thermogravimetric and mass spectral analysis, and differential scanning calorimetry. In the temperature range 140–240°C, β-Mn(C5H7O2)3 melts to form Mn(C5H7O2)2. At temperatures of 500–550°С, Mn(C5H7O2)2 decomposes to a mixture of MnO, Mn3O4, Mn2O3, and carbon.

Macroscopic superlubricity enabled by the tribopair of nc-Ag/MoS2 and hydrogenated graphitic-like carbon films under high contact stress

Solid lubricants have superior environmental adaptability and can be widely used in space machinery under extreme harsh working conditions, including high contact pressure, high or cryogenic temperature, long working duration, etc. Loose-structured molybdenum disulfide (MoS2) film usually has poor load-bearing capacity, while low-hydrogenated graphitic-like carbon (GLCH) film is difficult to construct low-sheared frictional interfaces under dry inert atmosphere. In this paper, the heterogeneous interface was built up by combining nano-crystallized silver-doped MoS2 (nc-Ag/MoS2) and GLCH films to achieve superlubricity (coefficient of friction, COF = 0.006) under the ultra-high contact stress of 2.33 GPa. The results emphasize that the GLCH film with a low hydrogen content among the hydrogenated amorphous carbon (a-C:H) films is more likely to be low-friction and anti-wear when paired with nc-Ag/MoS2 film. Moreover, the nc-Ag/MoS2 film has potential to obtain the high load-bearing capacities and induce an appropriate graphitization of GLCH film in the heterogeneous interface system, obtaining superlow friction in contrast to the homogeneous self-mated GLCH tribopair. Additionally, this heterogeneous interface can achieve superlubricity (COF = 0.007) for more than 50,000 sliding cycles without failure. This study has important application significance in space machinery and can provide theoretical guidance and new paths for future solid lubrication technology.

Single nanosized graphene/TiOx multi-shells on TiO2 core via rapid-concomitant reaction pathway on metal oxide/polymer interface

A novel design has been proposed for a facile and rapid build-up of highly tailorable nanostructured multishells on metal oxide particles (graphene/TiOx@TiO2) under a dry inert atmosphere to maximize the visible-light photocatalytic performance. We also thoroughly and systematically investigated the as-prepared nanostructured particle surface and the mechanisms of the extraordinary in-situ graphene growth on the TiOx@TiO2 nanoparticles achieved by a rapid-concomitant reaction in the metal oxide (TiO2)/polymer (polymethyl methacrylate) interface under microwave irradiation. The as-prepared composite materials are also found to perform a better photocatalytic activity in comparison to the traditional synthesis pathway for degradation of organic pollutants under visible light, associated with the synergetic effects of homo-/hetero-junction on TiO2.

Quantitative amplitude-modulation scanning Kelvin probe microscopy via the second eigenmode excitation

Amplitude modulation scanning Kelvin probe microscopy (AM-SKPM) is widely used to measure the contact potential difference (CPD) between probe and samples in ambient or dry inert atmosphere. However, AM-SKPM is generally considered quantitatively inaccurate due to crosstalk between the cantilever and the sample. Here we demonstrate that the accuracy of AM-SKPM-based CPD measurements is drastically improved by exciting the SKPM probe at its second eigenmode. In the second eigenmode of oscillation, there exists a stationary node at the cantilever towards its free end, across which the displacement bears opposite signs; therefore driving the SKPM probe at its second eigenmode helps to partially cancel the virtual work done by the cantilever and reduce the crosstalk effect. The improvement in accuracy is experimentally confirmed with interdigitating electrodes calibration samples as well as practical samples such as the cross-section of wafer-bonded GaAs/GaN heterojunction.

Solar and Visible Light Assisted Peptide Coupling

AbstractAmino acid and peptide couplings are widely used in fields related to pharma and materials. Still, current peptide synthesis continues to rely on the use of expensive, water sensitive, and waste‐generating coupling reagents, which are often prepared in multi‐step sequences and used in excess. Herein is described a peptide coupling reaction design that relies mechanistically on sun‐light activation of a 4‐dimethylamino‐pyridine–alkyl halide charge‐transfer complex to generate a novel coupling reagent in situ. The resulting coupling method is rapid, does not require dry solvents or inert atmosphere, and is compatible with all the most common amino acids and protecting groups. Peptide couplings can be run on gram‐scale, without the use of special equipment. This method has a significantly reduced environmental and financial footprint compared to standard peptide coupling reactions. Experimental and computational studies support the proposed mechanism.

Solar and Visible Light Assisted Peptide Coupling.

Amino acid and peptide couplings are widely used in fields related to pharma and materials. Still, current peptide synthesis continues to rely on the use of expensive, water sensitive, and waste-generating coupling reagents, which are often prepared in multi-step sequences and used in excess. Herein is described a peptide coupling reaction design that relies mechanistically on sun-light activation of a 4-dimethylamino-pyridine-alkyl halide charge-transfer complex to generate a novel coupling reagent in situ. The resulting coupling method is rapid, does not require dry solvents or inert atmosphere, and is compatible with all the most common amino acids and protecting groups. Peptide couplings can be run on gram-scale, without the use of special equipment. This method has a significantly reduced environmental and financial footprint compared to standard peptide coupling reactions. Experimental and computational studies support the proposed mechanism.

Optical Carbon Dioxide Detection in the Visible Down to the Single Digit ppm Range Using Plasmonic Perfect Absorbers.

To tackle climate change and reduce CO2 emissions, it is important to measure CO2 output precisely. Even though there are many different techniques, no simple and cheap optical method in the visible is available. This work studies plasmonically enhanced optical carbon dioxide sensors in the visible wavelength range. The sensor samples are based on an inert plasmonic perfect absorber, which can be easily and cheaply fabricated by colloidal etching lithography. A CO2-sensitive polyethylenimine (PEI) layer is then spin-coated on top to complete the samples. The samples are examined continuously by microspectroscopy during different CO2 exposures to track spectral changes, particularly the position of the resonance centroid wavelength. The samples exhibit a resonance shift of up to 7 nm, depending on the CO2 concentration and the temperature. The temperature influences the rise time as well as the sensitive concentration range. The concentration dependence of the resonance shift overall follows the shape of a Langmuir isotherm, which includes a nearly linear relation at lower concentrations and elevated temperatures and a saturating behavior at higher concentrations and lower temperatures. The results indicate that a sensitivity in the full range from 100 vol % to below 1 ppm can be achieved. The samples degenerate in a dry inert atmosphere in a matter of days but are useable over multiple weeks when exposed to humidity and CO2. The PEI reacts very selectively to CO2, showing no response to CO, NH3, NO2, CH4, H2, and only a very small response to O2. Overall, polyethylenimine is very promising as a CO2-sensitive material for many practical sensing applications over a wide range of concentrations. An adjustment of the temperature is mandatory to control the sensitivity and response time.

Garnet-Type Li7La3Zr2O12 / Lithium Metal Interface: Microstructure and Electrochemical Properties in Solid State Batteries

All-solid-state lithium ion batteries may overcome safety issues in future energy storage systems, when a non-flammable solid electrolyte instead of a liquid electrolyte is applied. Garnet-type Li7La3Zr2O12 (LLZO) is an encouraging choice due to its high Li+ conductivity and its chemical stability against lithium metal [1]. However, low-resistance LLZO/Li interfaces are deteriorated by incomplete adhesion of lithium metal onto LLZO and by surface contamination [2]. The resulting inhomogeneous distribution of contact areas may be more prone to dendrite formation. Previous studies [3,4] indicate that LLZO/Li interface quality is significantly improved by metallic buffer layers.In this study, we aim for a reliable preparation of low-resistance interfaces between solid electrolyte and lithium metal. At first, magnetron sputtering is applied to deposit an indium buffer layer of 50 to 500 nm thickness onto the polished and cleaned electrolyte surface. For cell assembly, lithium foil is put on both sides of an In-coated LLZO pellet and the test cell is heated to 220°C in argon atmosphere. After that, microstructure and electrochemical properties of the symmetric cells are analyzed. We improved cross-section sample preparation to inspect the quality of LLZO/In/Li interfaces over hundreds of µm. Scanning electron microscopy (SEM, cf. figure 1) confirms excellent adhesion between lithium and LLZO. We use a dry inert atmosphere during preparation, handling and transfer of our samples to avoid artifacts and sample degradation. The FEI Helios G4 FX microscope enables correlative SEM imaging by simultaneous acquisition of up to four different detector signals for interface topography and material contrast. Local chemical composition at the interface is analyzed by energy dispersive X-ray spectroscopy and electron-beam damage is minimized for SEM imaging by selecting optimum electron energies.Electrochemical impedance spectroscopy (EIS) followed by data evaluation via the distribution of relaxation times (DRT) and equivalent circuit modelling [5] deliver the proportional contributions of grain, grain boundaries and interfaces to the total impedance of symmetric cells (Li/In/LLZO/In/Li). Interface microstructures and EIS measurements are correlated for samples with different buffer layer characteristics to allow targeted optimization. We compare the pristine state of the test cells to samples that have been cycled with different current densities.

Silver(I)‐Catalyzed Regioselective Synthesis of Dihydrofuro[3,4‐b]quinolines from o‐Alkynylquinoline‐MBH Adducts and Evaluation of their Photophysical Properties

AbstractA simple and facile approach is described for the regioselective synthesis of dihydrofuro[3,4‐b]quinolines from ortho‐alkynylquinoline‐Morita‐Baylis‐Hillman adducts under mild reaction conditions. Interestingly, in case of aromatic alkynes, 5‐exo‐dig cyclization was observed, while in case of aliphatic long chain alkynes, 6‐endo‐dig cyclized products were obtained. The present approach does not require any dry conditions, tedious work‐up or inert atmosphere for the production of dihydrofuro[3,4‐b]quinolines. The exact structures and stereochemistry of the synthesized molecules were assigned by NMR and X‐ray crystallographic analysis. Their photophysical properties were also evaluated.

Thermal behavior and microstructure of the Li3PS4–ZnO composite electrolyte

Li3PS4 (LPS) glasses in a Li2S–P2S5 binary system demonstrate promise as solid electrolytes for the development of all-solid-state lithium batteries due to their high electrochemical stability and ionic conductivity. However, sulfide electrolytes are hygroscopic; hence, these electrolytes are treated in a dry inert gas atmosphere, thereby increasing the process costs. To improve the chemical stability of LPS in air, in this study, composite electrolytes comprising LPS and ZnO, which is a H2S absorbent, were synthesized. In addition, the effects of the addition of ZnO on the thermal behavior and electrical properties of LPS glasses were investigated. Differential scanning calorimetry (DSC) measurements and ex situ TEM images revealed that the increase in the ZnO content significantly affects the exothermal behavior of LPS glass. In particular, LPS glasses comprising greater than 50 mol% of ZnO exhibit multiple exothermic reactions at temperatures of greater than ca. 250 °C. This result revealed that in LPS–ZnO electrolytes, 10 or 20 mol% of ZnO is an optimum additive to ensure a good balance among the thermal stability and chemical stability in air and conductivity.

Liquid window of some biologically-active ionic liquids

The liquid range of six Ionic Liquids (ILs) with potential uses in biological applications was determined. The lower limit, given by solid-liquid transitions, was determined using differential scanning calorimetry (DSC). The transitions of four ILs were reported for first time, others have shown good agreement with literature values. The upper limit of the liquid range was determined using thermogravimetric analysis (TGA). Dynamic and isothermal methods have been combined to estimate the maximum operation temperature. Dry air and inert atmosphere were attempted with no significant differences between the obtained data. Results are in good agreement with the scarce information found in literature while in most cases upper limit of the liquid range was studied for first time. Measures throw interesting information on cation and anion effect over the studied properties.

Room temperature sintering of polar ZnO nanosheets: I-evidence.

Polar ZnO nanosheets of a high specific surface area (∼120 m2 g-1) were subjected to storage under different atmospheres at room temperature and analyzed for changes in their textural and crystal properties. During their storage under laboratory conditions (in closed transparent polypropylene vials kept under the light of the laboratory on worktop tables) the nanosheets lost up to 75% of their specific surface area in approximately two months, with most of the loss occurring during the first two weeks. The narrow mesoporosity (∼5 nm pore size) became filled with ZnO during the process. No loss or gain in weight was detected. The loss of specific surface area took place under all of the atmospheres assayed, in the following order: moist air (with or without light) > moist CO2-free atmosphere (with or without light and/or oxygen) > dry CO2-free oxygen-containing atmosphere (with or without light) > dry inert atmosphere (with light) > dry inert atmosphere (in the dark). During storage the ZnO crystals grew mainly by the partial merging of their polar surfaces in a process triggered by the action of moisture, oxygen and, in the absence of these two agents, light. The mechanism of this intriguing phenomenon will be analyzed in detail in the second part of this work.

Intramolecular Csp2-Csp2 Friedel-Crafts Arylation: Substrate- and Condition-Controlled Divergent Synthesis of Fused-β-carbolines.

A triple cooperative catalysis-mediated multicomponent reaction between 1-formyl-N-substituted-β-carbolines, a terminal alkyne, and a secondary amine allows access to unprecedented polycyclic β-carbolines via sequential A3-coupling and an intramolecular Csp2-Csp2 Friedel-Crafts arylation reaction. The reaction is successful in a dry inert atmosphere only with substrates bearing a methoxy-substituted benzyl group at the indole nitrogen. Conversely, treating 3-aminoindolizino[8,7-b]indoles (obtained after A3-coupling) with acid in the presence of H2O in air offers a general route to natural-alkaloid-like products.

Introducing deep eutectic solvents to polar organometallic chemistry: chemoselective addition of organolithium and Grignard reagents to ketones in air.

Despite their enormous synthetic relevance, the use of polar organolithium and Grignard reagents is greatly limited by their requirements of low temperatures in order to control their reactivity as well as the need of dry organic solvents and inert atmosphere protocols to avoid their fast decomposition. Breaking new ground on the applications of these commodity organometallics in synthesis under more environmentally friendly conditions, this work introduces deep eutetic solvents (DESs) as a green alternative media to carry out chemoselective additions of ketones in air at room temperature. Comparing their reactivities in DES with those observed in pure water suggest that a kinetic activation of the alkylating reagents is taking place, favoring nucleophilic addition over the competitive hydrolysis, which can be rationalized through formation of halide-rich magnesiate or lithiate species.

Introducing Deep Eutectic Solvents to Polar Organometallic Chemistry: Chemoselective Addition of Organolithium and Grignard Reagents to Ketones in Air

AbstractDespite their enormous synthetic relevance, the use of polar organolithium and Grignard reagents is greatly limited by their requirements of low temperatures in order to control their reactivity as well as the need of dry organic solvents and inert atmosphere protocols to avoid their fast decomposition. Breaking new ground on the applications of these commodity organometallics in synthesis under more environmentally friendly conditions, this work introduces deep eutetic solvents (DESs) as a green alternative media to carry out chemoselective additions of ketones in air at room temperature. Comparing their reactivities in DES with those observed in pure water suggest that a kinetic activation of the alkylating reagents is taking place, favoring nucleophilic addition over the competitive hydrolysis, which can be rationalized through formation of halide‐rich magnesiate or lithiate species.

Hydrosilylation of Internal Alkynes Catalyzed by Tris‐ Imidazolium Salt‐Stabilized Palladium Nanoparticles

AbstractPalladium nanoparticles stabilized with tris‐imidazolium tetrafluoroborates catalyze the stereoselective hydrosilylation of internal alkynes in a dry inert atmosphere to give (E)‐vinylsilanes in excellent yields. In the presence of controlled amounts of water a transfer hydrogenation reaction takes place with the formation of (Z)‐alkenes or the corresponding alkanes.magnified image

CuBr-catalyzed cascade reaction of 2-substituted-3-(1-alkynyl)chromones to synthesize functionalized 3-acylfurans

Abstract A highly efficient CuBr-catalyzed domino reaction of 2-substituted-3-(1-alkynyl)chromones to synthesize functionalized 3-acylfurans has been developed. The reaction is mild, environmentally friendly and easily handled without the necessity for dry solvents and inert atmosphere.

ChemInform Abstract: Rapid, Clean and Efficient One‐Pot Synthesis of Thiopyrano[2,3‐b]quinolines via Domino Michael Addition/Cyclization Reactions.

AbstractThe sequence proceeds smoothly and does not require dry solvent or inert atmosphere.