Room Temperature Reaction Research Articles

Mild and Rapid Light-Driven Suzuki-Miyaura Reactions Catalyzed by AuPd Nanoparticles in Water at Room Temperature.

Organic reactions carried out in water under mild conditions are state-of-the-art in terms of environmentally benign chemical processes. In this direction, plasmonic catalysis can aid in accomplishing such tasks. In the present work, cyclodextrin-mediated AuPd bimetallic nanoparticles (NPs) were applied in room-temperature aqueous Suzuki-Miyaura reactions aiming at preparing biaryl products based on fluorene, isatin, benzimidazole and resorcinol, with yields of 77 % up to 95 %. AuPd NPs were revealed to be a physical mixture of Au and Pd particles circa 20 and 2 nm, respectively, through X-ray diffraction, dynamic light scattering, UV-Vis spectroscopy and transmission electron microscopy analyses.

Size Selectivity in Heterolanthanide Molecular Complexes with a Ditopic Ligand.

The similar reactivity of lanthanides generally leads to statistically populated polynuclear complexes, making the rational design of ordered hetero-lanthanide compounds extremely challenging. Here we report on the site selectivity in hetero-lanthanide tetranuclear complexes afforded by the relatively simple ditopic pyterpyNO ligand (4'-(4-pyridil)-2,2':6',2"-terpyridine N-oxide). The sequential room temperature reaction of RE2 (tta)6 (pyterpyNO)2 (where RE=Y, (1); Eu, (2), Dy, (3) Htta=2-thenoyltrifluoroacetone) with La(tta)3 dme (dme=dimethoxyethane) yielded Y2 La2 (tta)12 (pyterpyNO)2 (4), Dy2 La2 (tta)12 (pyterpyNO)2 (5) and Eu2 La2 (tta)12 (pyterpyNO)2 (6). Single crystals X-ray diffraction studies showed that 4, 5 and 6 are isostructural, featuring a tetranuclear structure with two different metal coordination sites with coordination numbers 8 (CN8) and 9 (CN9). The two smaller cations are mainly bridged by the O-donor atoms of the NO groups of two pyterpyNO ligands (CN8), while the larger lanthanum centres are bound by a terpyridine unit (CN9). Size selectivity has been studied with structural and magnetic studies in the solid state and through 19 F NMR and photoluminescence studies in solution, showing a direct dependence on the difference of ionic radii of the ions and yielding a 91 % selectivity for 4. Furthermore, 19 F NMR, X-ray and PL studies pointed out that the nature of the product is independent from the synthetic route for compound Eu2 Y2 (tta)12 (pyterpyNO)2 (7), keeping the ion selectivity also for a self-assembly reaction. Unexpectedly, these studies have evidenced that selectivity is not exclusively governed by electrostatic interactions related to size dimensions.

Synthesis of 4H-3,1-Benzothiazin-4-Ones via C-N/C-S Bond Forming Reactions

A Phosphine-free and effective process has been expressed for the formulation of N,S-heterocycles following a C-N/C-S bond forming reactions. The described process operates through EDC-HCl-mediated heterocyclization of diverse isothiocyanates and bis-nucleophiles to deliver 1,3-thiazinone derivatives, which eliminates the use of hazardous reagents. The developed protocol was found applicable over a wide range of substrates in delivering N,S-heterocycles in excellent yields at room temperature and short reaction time.

PdAu Nanosheets for Visible-Light-Driven Suzuki Cross-Coupling Reactions.

Combining a two-dimensional (2D) morphology and plasmonic photocatalysis represents an efficient design for light-driven organic transformations. We report a one-pot synthesis of surfactant templated PdAu nanosheets (NSs). Transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) analyses show the formation of 2D PdAu structures was initiated through nanoparticle seeds dispersed in the alkyl ammonium salt surfactant which acted as a template for the growth into NSs. The PdAu NSs were used for visible-light-enhanced Suzuki cross coupling. The PdAu bimetallic NSs outperformed monometallic Pd NSs and commercial Pd/C in room-temperature Suzuki cross-coupling reactions. The high catalytic activity is attributed to a combination of the 2D morphology giving rise to plasmon-enhanced catalysis and a high density of surface atoms, the electron-rich Pd surface due to alloying, and the presence of weakly bound amines. A comparative study of surfactant-assisted NSs and CO-assisted NSs was also carried out to assess the influence of surface ligands on the catalytic and photocatalytic enhancement of NSs with similar morphology. The surfactant-assisted NSs showed substantially superior performance compared to the CO-assisted for room-temperature Suzuki coupling reactions.

The chemistry of κ2-N,S-chelated Ru(II) complexes with 1,4-diethynylbenzene

The chemistry of κ2-N,S-chelated Ru(II) complexes, [Cp*RuPPh3(κ2-N,S-(NC7H4S2)] (Cp*=ƞ5-C5Me5), 1a and [PPh3{κ2-N,S-(NS2C7H4)}Ru{κ3-H,S,S-H2B(NC7H4S2)2}], 1b has been explored with a terminal alkyne 1,4-diethynylbenzene. For example, the room-temperature reaction of Cp* based κ2-N,S-chelated Ru(II) species 1a with 1,4-diethynyl-benzene yielded [RuCp*(κ1-N,S-C7H4NS2)C7H4NS2-(E)-N−C=CHC8H5], 2. On the other hand, although treatment of 1b with 1,4-diethynylbenzene at room temperature showed no reactivity, thermolysis led to the formation of two borate complexes, [PPh3{C7H4NS2-(E)-N−C=CHC8H5}Ru{κ3-H,S,Sʹ-H2B(C7H4NS2)2}], 3 and [PPh3(κ2-N,S-C7H4NS2) Ru{κ3-S,Sʹ,Sʹʹ-HB(C7H4NS2)3}], 4, albeit in poor yields. Both the Ru(II) species 2 and 3 contain a five-membered ruthenacycle with an exocyclic C=C moiety attached to carbon atom. In complex 4, the ruthenium center is stabilized by hydrotrisborate, phosphine, and hemilabile one N,S-chelating ligand. The key feature of 4 is the coordination of the boron atom to the metal center through a common sulphur atom of the 2-mercaptobenzothiazole ligand. Characterization of these Ru(II) species has been carried out by various spectroscopic techniques and single-crystal X-ray diffraction analysis for 4. In addition, Density Functional Theory (DFT) calculations were further performed to provide insight into the bonding and electronic structures of these complexes.

Versatile Inorganic Subnanometer Nanowire Adhesive.

Adhesives are applied extensively in daily life and industries, and people have developed numerous commercial polymeric adhesives. However, in most cases, these adhesives work on dry surfaces in air and form permanent bonds with the substrates, limiting the applications of adhesives. Inspired by the innate adhesive functions of some animals, such as geckos, spiders, mussels, and clingfish, scientists have developed various adhesive compositions and structures to meet various conditions. Here, we show a versatile subnanometer nanowire (SNW) adhesive with high strength and great reversibility, which could be prepared at a large scale through a facile room-temperature reaction. The SNW adhesive contacts the substrates at multiple sites due to the ultrahigh flexibility, and meanwhile, the multilevel interactions among the SNWs endow them with strong cohesion, so they exhibit good adhesive performance. This adhesive is applicable to various substrates, such as metals, polymers, and glass, and not only possesses good stability at room temperature in air but also is suitable for underwater environments and ultralow temperatures. Moreover, this adhesive could be easily recycled and removed from the substrates without any residue and damage. The SNW adhesive not only inspires the design of hierarchical adhesive structures with new contact modes but also has potential for practical applications.

Manipulating Reaction Intermediates to Aqueous-Phase ZnSe Magic-Size Clusters and Quantum Dots at Room Temperature.

It is not resolved which model describes better the aqueous-phase nucleation and growth of semiconductor quantum dots (QDs), the classical one-step one or the nonclassical multi-step one. Here, we design a room-temperature reaction to trap reaction intermediates in the prenucleation stage of ZnSe QDs (as a model system). We show that the trapped intermediate can transform to magic-size clusters (MSCs) via intra-molecular reorganization and can fragment to enable the growth of QDs. The MSCs exhibit a sharp optical absorption peaking at 299 nm, labelled MSC-299. The intermediate, the precursor compound (PC-299) of MSC-299, is optically transparent at 299 nm and to longer wavelengths. This intermediate forms in various Zn and Se reaction systems. The present study provides unambiguous evidence that the nonclassical and classical pathways are both necessary to explain the nucleation and growth of aqueous-phase QDs, with the former pathway favored more by high reaction concentrations.

Alloying Pd with Cu boosts hydrogen production via room-temperature electrochemical water-gas shift reaction

Room-temperature electrochemical water-gas shift (RT-EWGS) process provides a promising route for high purity hydrogen production under ambient conditions, in which the anodic carbon monoxide (CO) oxidation as the key and bottleneck-type reaction largely hinders the overall efficiency due to its sluggish reaction kinetics. It is of great significance to develop low cost and efficient anode electrocatalysts to enhance the hydrogen production via improving the CO oxidation activity, but it remains a great challenge. Herein, by alloying Pd with Cu, we achieve a high mass activity of 19.9 mA/mgPd for anodic CO oxidation at 0.3 V versus reversible hydrogen electrode (vs. RHE), which is over 330 times higher than that over pure Pd catalyst and significantly higher than the previously reported catalysts. Combined with density functional theory calculations, we find that the adsorbed CO (CO*) species is more likely to react with the adsorbed OH (OH*) rather than the OH- in the solution for PdCu alloy catalyst during the anodic CO oxidation process, and the introduction of Cu into Pd renders a weakened CO* adsorption along with an enhanced OH* adsorption, which significantly lower the overpotential via optimizing the anodic oxidation of CO pathway. This work provides a new direction for the design of efficient anode catalysts toward RT-EWGS with low energy input.

Constructing a defect-rich hydroxide nanoenzyme sensor based on dielectric barrier discharge microplasma etching for sensitive detection of thiamine hydrochloride and hydrogen peroxide

In this work, a novel approach was designed to fabricate a defect-rich hydroxide nanoenzyme sensor based on transition metal cobalt derived from metal-organic framework (MOF). Facile preparation was realized by room-temperature reaction and chemical etching via dielectric barrier discharge (DBD) microplasma, which possesses great chemical reactivity to obtain defect-rich and ultrathin structures. The prepared cobalt hydroxide (Co(OH)2) emerges with superior catalytic activity for thiamine hydrochloride (TCL) and hydrogen peroxide (H2O2) assay. The linear ranges were 0.0006 mM to 2.75 mM for TCL detection and 0.001 mM to 5.5 mM for H2O2 detection with low limit of detections (LODs) of 14 nM and 93 nM, respectively. Meanwhile, the as-prepared sensor provides excellent long-term durability (>25 days), as well as high sensitivity (12730 μA mM−1cm−2 and 5199.3 μA mM−1 cm−2) for TCL and H2O2 assay. TCL in serum samples has been detected with satisfactory results by the proposed material, while the H2O2 in Hela cells was also successfully measured. The developed sensor provides several advantages including simplicity, high sensitivity, and efficient preparation.

Locking volatile organic molecules by subnanometer inorganic nanowire-based organogels

The intermolecular forces among volatile organic molecules are usually weaker than water, making them more difficult to absorb. We prepared alkaline earth cations–bridged polyoxometalate nanoclusters subnanometer nanowires through a facile room-temperature reaction. The nanowires can form three-dimensional networks, trapping more than 10 kinds of volatile organic liquids effectively with the mass fraction of nanowires as low as 0.53%. A series of freestanding, elastic, and stable organogels were obtained. We prepared gels that encapsulate organic liquids at the kilogram scale. Through removing solvents in gels by means of distillation and centrifugation, the nanowires can be recycled more than 10 times. This method could be applied to the effective trapping and recovery of organic liquids.

Active sites and deactivation of room temperature CO oxidation on Co3O4 catalysts: combined experimental and computational investigations

Co3O4 is a well-known low temperature CO oxidation catalyst, but it often suffers from deactivation. We have thus examined room temperature (RT) CO oxidation on Co3O4 catalysts by operando DSC, TGA and MS measurements, as well as by pulsed chemisorption to differentiate the contributions of CO adsorption and reaction to CO2. Catalysts pretreated in oxygen at 400 °C are most active, with the initial interaction of CO and Co3O4 being strongly exothermic and with maximum amounts of CO adsorption and reaction. The initially high RT activity then levels-off, suggesting that the oxidative pretreatment creates an oxygen-rich reactive Co3O4 surface that upon reaction onset loses its most active oxygen. This specific active oxygen is not reestablished by gas phase O2 during the RT reaction. When the reaction temperature is increased to 150 °C, full conversion can be maintained for 100 h, and even after cooling back to RT. Apparently, deactivating species are avoided this way, whereas exposing the active surface even briefly to pure CO leads to immediate deactivation. Computational modeling using DFT helped to identify the CO adsorption sites, determine oxygen vacancy formation energies and the origin of deactivation. A new species of CO bonded to oxygen vacancies at RT was identified, which may block a vacancy site from further reaction unless CO is removed at higher temperature. The interaction between oxygen vacancies was found to be small, so that in the active state several lattice oxygen species are available for reaction in parallel.

Functionalization of magnetic nanoparticles by creatine as a novel and efficient catalyst for the green synthesis of 2-amino-4H-chromene derivatives

By employing the naturally-originated molecule of creatine, Fe3O4@SiO2-creatine as an environmentally benign magnetic organometallic nanobiocatalyst was successfully prepared via a convenient and green route. Then to acquire an inclusive comprehension of different properties of the catalyst, it was studied by various characterization techniques such as FT‐IR, FE-SEM, TEM, EDX, XRD, and VSM analyses. It was found that the size distribution of nanoparticles was an average diameter size of 70 nm. To examine the catalytic activity, it was applied in sequential knoevenagel condensation-Michael addition room temperature reaction of dimedone, malononitrile, and different substituted aromatic aldehydes to produce a variety of 2-amino-tetrahydro-4H-chromene-3-carbonitrile derivatives in a single step. Among the multiple outstanding advantages that can be mentioned for this work, some of the most noticeable ones include: affording the products in short reaction times with high yields, operating the reaction at ambient conditions and ease of catalyst separation.

Bimetallic Fe–Cu metal organic frameworks for room temperature catalysis

Bimetallic Fe–Cu MOF was effectively synthesized through a one‐pot solvothermal process and successfully characterized by TEM, XPS, SEM, XRD, BET, EDX, elemental mapping, and FT‐IR analysis. This bimetallic MOF was employed as a catalyst in the reduction of nitroarenes at room temperature and as well as in the reduction of dyes, for example, methyl orange (MO) and methylene blue (MB). Results pointed to Fe–Cu MOF exhibiting outstanding catalytic performance for both room temperature reactions. The catalytic activity of Fe–Cu MOF in comparison with Fe‐MOF and Cu‐MOF in the nitroarenes reduction indicated a superior activity compared with single‐metal MOFs. Activity of Fe–Cu MOF catalyst did not change after its recycling and reusing for seven consecutive cycles in nitrobenzene reduction.

Ceramic Catalysts: Materials, Synthesis, and Applications

We report a facile synthesis of nanostructured Cu-incorporated SnO2. Aggregates composed of uniform ∼ 5 nm-sized nanoparticles were obtained through a simple room-temperature reaction between CuO and SnC2O4 in aqueous solution. The material is single-phase with copper incorporated mainly as Cu+. The synthesis approach also allows mixing with CuO to prepare SnO2/CuO nanocomposites. The synthesized materials show an improved cycle performance as anode materials in lithium ion batteries due to an improved morphology and in situ formation of metallic copper upon cycling (in the voltage range 0.05–1.1 V vs. Li/Li+).

Encina slates plastics recycling plant as Brightmark cancels

We report a facile synthesis of nanostructured Cu-incorporated SnO2. Aggregates composed of uniform ∼ 5 nm-sized nanoparticles were obtained through a simple room-temperature reaction between CuO and SnC2O4 in aqueous solution. The material is single-phase with copper incorporated mainly as Cu+. The synthesis approach also allows mixing with CuO to prepare SnO2/CuO nanocomposites. The synthesized materials show an improved cycle performance as anode materials in lithium ion batteries due to an improved morphology and in situ formation of metallic copper upon cycling (in the voltage range 0.05–1.1 V vs. Li/Li+).

Ozone Decomposition below Room Temperature Using Mn-based Mullite YMn2O5.

A super-low-temperature ozone decomposition is realized without energy consumption on a ternary oxide catalyst mullite YMn2O5 for the first time. The YMn2O5 oxide catalyzed ozone decomposition from a low temperature of -40 °C with 29% conversion (reaction rate: 1534.2 μmol g-1 h-1) and quickly reached 100% (5459.5 μmol g-1 h-1) when warmed up to -5 °C. The superior low-temperature performance over YMn2O5 could surpass that of the reported ozone decomposition catalysts. The structure and element valence characterizations confirmed that YMn2O5 remained the same after 100 h of room-temperature reaction, indicating excellent durability of the catalyst. O2-TPD (O2-temperature-programmed desorption) showed that the active sites are the Mn3+ sites bonded with singly coordinated oxygen on the surface. Combined with in situ Raman measurements and density functional theory calculations, we found that the ozone decomposition reaction on YMn2O5 showed a barrier of only 0.29 eV, following the Eley-Rideal (E-R) mechanism with a rate-limiting step of intermediate O22- desorption. The low barrier minimizes the accumulation of intermediate products and realizes the fast O3 decomposition even at super-low temperatures. Fundamentally, the moderate Mn-O bonding strength in the low-symmetry ternary oxides is crucial to produce singly coordinated active species on the surface responsible for the efficient ozone degradation at low temperatures.

Reactions of a Dimethylxanthene‐Derived Frustrated Lewis Pair with Silanes and Stannanes

AbstractThe reactivity towards Si−H and Sn−H bonds of a dimethylxanthene‐based frustrated Lewis pair featuring −PiPr2 and −B(C6F5)2 functions in the 4‐, and 5‐positions is reported. In the case of silanes, greater steric bulk appears to impede reactivity, with only PhSiH3 and SiH4 showing unambiguous evidence for Si−H bond activation. In the case of PhSiH3, the silylphosphonium borohydride 1iPr(SiH2Ph)(H) is formed by Si−H bond activation across the P/B manifold. 1iPr(SiH2Ph)(H) loses PhSiH3 in hydrocarbon solution and therefore can only be crystallized from the neat silane. On heating, it undergoes a metathesis process leading to installation of the −SiH2Ph function at the 5‐position of the xanthene scaffold, with accompanying migration of the boryl group (as Piers’ borane, HB(C6F5)2) to the phosphine. Similar chemistry is observed with SiH4 (although occurring much more readily), and such processes are thought to be mechanistically similar to related rearrangements occurring with the boranes HBpin and HBcat. By contrast, the activation of the weaker Sn−H bonds found in stannanes occurs more readily, even for bulkier substrates, and the stannyl‐phosphonium borohydrides 1iPr(SnnBu3)(H) and 1iPr(SnPh3)(H) are obtained from the room temperature reactions with nBu3SnH and Ph3SnH, respectively.

Supramolecular Template-Assisted Catalytic [2+2] Photocycloaddition in Homogeneous Solution

Supramolecular Template-Assisted Catalytic [2+2] Photocycloaddition in Homogeneous Solution

Reversible polymerization of carbon dots based on dynamic covalent imine bond

Carbon dots (CDs), as new type of carbon-based nanoparticles, are considered to be an aggregate with irreversible polymerization. Achieving the reversible tunability of CDs luminescence based on their reversible polymerization is a challenging subject. Herein, we, for the first time, design and construct the blue-emitting CDs with reversible polymerization by a room-temperature Schiff base reaction between tannic acid and ethylenediamine. The formation of CDs is proven to be due to the crosslinking polymerization of precursors caused by imine bond. As a dynamic covalent bond, imine bond endows CDs with controllable structural transformation properties, and the prepared CDs can be depolymerized and polymerized reversibly by pH-controlled imine bond cleavage and re-formation. These properties of reversible fluorescence photoswitching make the CDs have a good application prospect in reversible information encryption.

Thermal annealing effects on palladium-decorated gold nanoparticle catalysts

Palladium metal supported on gold in the form of surface ensembles have enhanced catalytic properties compared to monometallic Pd, as exemplified by Pd-decorated Au nanoparticles (Pd-on-Au NPs) for various room-temperature reactions. Whereas the catalytic properties and nanostructure of Pd-on-Au NPs are not known at higher temperatures, this work focuses on thermal annealing effects on the Pd-on-Au NP nanostructure, bimetal distribution, and room-temperature water-phase trichloroethene hydrodechlorination (TCE HDC) as the model reaction. Analysis of the average coordination environment of Pd and Au atoms through x-ray absorption spectroscopy showed that as-synthesized Pd-on-Au NPs transitioned from a Au core/Pd shell structure to Au-rich core/PdAu surface alloy or PdAu mixed alloy structures depending on the Pd surface coverage (30–150 sc%) and annealing temperature (100–400 °C). The HDC activity strongly correlated with Pd ensemble size, where the as-formed Pd islands exhibited one order of magnitude enhanced activity compared to monometallic Pd. Higher annealing temperatures led to a surface/mixed alloy structure with smaller Pd ensemble size, resulting in lower activity but still ∼3 times more active than monometallic Pd. These results illustrate the importance of catalyst structure on activity and the usefulness of metal-decorated metal catalysts for higher-temperature reactions.