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Heterogeneous catalytic ammoxidation provides an eco‐friendly route for the cyanide‐free synthesis of nitrile compounds, which are important precursors for synthetic chemistry and pharmaceutical applications. However, in general such a process requires high pressures of molecular oxygen at elevated temperatures to accelerate the oxygen reduction and imine dehydrogenation steps, which is highly risky in practical applications. Here, we report an electric field enhanced ammoxidation system using a supported Fe clusters catalyst (Fe/NC), which enables efficient synthesis of nitriles from the corresponding aldehydes under ambient air pressure at room temperature (RT). A synergistic effect between the external electric field and the Fe/NC catalyst promotes the ammonia activation and the dehydrogenation of the generated imine intermediates and avoids the unwanted backwards reaction to aldehydes. This electric field enhanced ammoxidation system presents high efficiency and selectivity for the conversion of a series of aldehydes under mild conditions with high durability, rendering it an attractive process for the green synthesis of nitriles with fragile functional groups. [ABSTRACT FROM AUTHOR]

Two‐dimensional (2D) semiconductors including transition metal dichalcogenides (TMDCs) have gained attention in optoelectronics for their extraordinary properties. However, the large amount and locally distributed lattice defects affect the optical properties of 2D TMDCs, and the defects originate from unstable factors in the synthesis process. In this work, we develop a method of pre‐melting and resolidification of chalcogen precursors (sulfur and selenium), namely resolidified chalcogen, as precursor for the chemical vapor deposition growth of TMDCs with ultrahigh quality and uniformity. Taking WS2 as an example, the monolayer WS2 shows uniform fluorescence intensity and a small full‐width at half‐maximum of photoluminescence peak at low temperatures with an average value of 13.6±1.9 meV. The defect densities at the interior and edge region are both low and comparable, i.e., (9±3)×1012 cm−2 and (10±4)×1012 cm−2, indicating its high structural quality and uniformity. This method is universal in growing high quality monolayer MoS2, WSe2, MoSe2, and will benefit their applications. [ABSTRACT FROM AUTHOR]

Aryl fluorides are expected to be useful as radiolabeling precursors due to their chemical stability and ready availability. However, direct radiolabeling via carbon‐fluorine (C−F) bond cleavage is a challenging issue due to its significant inertness. Herein, we report a two‐phase radiosynthetic method for the ipso‐11C‐cyanation of aryl fluorides to obtain [11C]aryl nitriles via nickel‐mediated C−F bond activation. We also established a practical protocol that avoids the use of a glovebox, except for the initial preparation of a nickel/phosphine mixture, rendering the method applicable for general PET centers. This method enabled the efficient synthesis of diverse [11C]aryl nitriles from the corresponding aryl fluorides, including pharmaceutical drugs. Stoichiometric reactions and theoretical studies indicated a significant promotion effect of lithium chloride on the oxidative addition, affording an aryl(chloro)nickel(II) complex, which serves as a precursor for rapid 11C‐cyanation. [ABSTRACT FROM AUTHOR]

The aging of precursor solutions is the major stumbling block for the commercialization of perovskite solar cells (PSCs). Herein, for the first time we used the state‐of‐the‐art in situ liquid time‐of‐flight secondary ion mass spectrometry to molecularly explore the perovskite precursor solution chemistry. We identified that the methylammonium and formamidinium cations and the I− anion are the motivators of the aging chemistry. Further, we introduced two kinds of Lewis bases, triethyl phosphate (TP) and ethyl ethanesulfonate (EE), as new additives in the solution and unraveled that both of them can protect the reactive cations from aging through weak interactions. Significantly, TP is superior to EE in enhancing long‐term solution stability as it can well‐maintain the internal interaction structures within the solution phase. The PSC derived from a fresh TP‐doped solution delivered a high power conversion efficiency of 23.06 %, 92.23 % of which remained in that from a 21‐day‐old solution. [ABSTRACT FROM AUTHOR]

Metabolic theories for the origin of life posit that inorganic catalysts enabled self‐organized chemical precursors to the pathways of metabolism, including those that make genetic molecules. Recently, experiments showing nonenzymatic versions of a number of core metabolic pathways have started to support this idea. However, experimental demonstrations of nonenzymatic reaction sequences along the de novo ribonucleotide biosynthesis pathways are limited. Here we show that all three reactions of pyrimidine nucleobase biosynthesis that convert aspartate to orotate proceed at 60 °C without photochemistry under aqueous conditions in the presence of metals such as Cu2+ and Mn4+. Combining reactions into one‐pot variants is also possible. Life may not have invented pyrimidine nucleobase biosynthesis from scratch, but simply refined existing nonenzymatic reaction channels. This work is a first step towards uniting metabolic theories of life's origin with those centered around genetic molecules. [ABSTRACT FROM AUTHOR]

Wearable personal protective equipment that is decorated with photoactive self‐cleaning materials capable of actively neutralizing biological pathogens is in high demand. Here, we developed a series of solution‐processable, crystalline porous materials capable of addressing this challenge. Textiles coated with these materials exhibit a broad range of functionalities, including spontaneous reactive oxygen species (ROS) generation upon absorption of daylight, and long‐term ROS storage in dark conditions. The ROS generation and storage abilities of these materials can be further improved through chemical engineering of the precursors without altering the three‐dimensional assembled superstructures. In comparison with traditional TiO2 or C3N4 self‐cleaning materials, the fluorinated molecular coating material HOF‐101‐F shows a 10‐ to 60‐fold enhancement of ROS generation and 10‐ to 20‐fold greater ROS storage ability. Our results pave the way for further developing self‐cleaning textile coatings for the rapid deactivation of highly infectious pathogenic bacteria under both daylight and light‐free conditions. [ABSTRACT FROM AUTHOR]

Hyperpolarization‐enhanced magnetic resonance imaging can be used to study biomolecular processes in the body, but typically requires nuclei such as 13C, 15N, or 129Xe due to their long spin‐polarization lifetimes and the absence of a proton‐background signal from water and fat in the images. Here we present a novel type of 1H imaging, in which hyperpolarized spin order is locked in a nonmagnetic long‐lived correlated (singlet) state, and is only liberated for imaging by a specific biochemical reaction. In this work we produce hyperpolarized fumarate via chemical reaction of a precursor molecule with para‐enriched hydrogen gas, and the proton singlet order in fumarate is released as antiphase NMR signals by enzymatic conversion to malate in D2O. Using this model system we show two pulse sequences to rephase the NMR signals for imaging and suppress the background signals from water. The hyperpolarization‐enhanced 1H‐imaging modality presented here can allow for hyperpolarized imaging without the need for low‐abundance, low‐sensitivity heteronuclei. [ABSTRACT FROM AUTHOR]

Presented here is a concise synthesis of secu′amamine A, and fluvirosaones A and B from readily available allosecurinine and viroallosecurinine. The key C2‐enamine derivative of (viro)allosecurinine, the presumed biosynthetic precursors of these natural products, was accessed, for the first time, by a VO(acac)2‐mediated regioselective Polonovski reaction. Formal hydration and 1,2‐amine shift of this pluripotent enamine compound afforded secu′amamine A. Formal oxidative [3+2] cycloaddition reaction between this enamine and TMS‐substituted methallyl iodide reagent paved the way to the precursors of fluvirosaones A and B. The relative stereochemistry at the C2 position of these advanced intermediates governs the fate of 1,2‐amine shift leading to fluvirosaones A and B. The syntheses of potential biosynthetic precursors and investigations of their chemical reactivities have provided insights regarding the biogenesis of these natural products. [ABSTRACT FROM AUTHOR]

A rhodium‐catalyzed remote C(sp3)−H borylation of silyl enol ethers (SEEs, E/Z mixtures) by alkene isomerization and hydroboration is reported. The reaction exhibits mild reaction conditions and excellent functional‐group tolerance. This method is compatible with an array of SEEs, including linear and branched SEEs derived from aldehydes and ketones, and provides direct access to a broad range of structurally diverse 1,n‐borylethers in excellent regioselectivities and good yields. These compounds are precursors to various valuable chemicals, such as 1,n‐diols and aminoalcohols. [ABSTRACT FROM AUTHOR]

Hole or electron doping of phases prepared by topochemical reactions (e.g. anion deintercalation or anion‐exchange) is extremely challenging as these low‐temperature conversion reactions are typically very sensitive to the electron counts of precursor phases. Herein we report the successful hole and electron doping of the transition‐metal oxyhydride LaSr3NiRuO4H4 by first preparing precursors in the range LaxSr4−xNiRuO8 0.5

Hole or electron doping of phases prepared by topochemical reactions (e.g. anion deintercalation or anion‐exchange) is extremely challenging as these low‐temperature conversion reactions are typically very sensitive to the electron counts of precursor phases. Herein we report the successful hole and electron doping of the transition‐metal oxyhydride LaSr3NiRuO4H4 by first preparing precursors in the range LaxSr4−xNiRuO8 0.5

The nucleation mechanism of crystals of small organic molecules, postulated based on computer simulations, still lacks experimental evidence. In this study we designed an experimental approach to monitor the early stages of the crystallization of ibuprofen as a model system for small organic molecules. Ibuprofen undergoes liquid–liquid phase separation prior to nucleation. The binodal and spinodal limits of the corresponding liquid–liquid miscibility gap were analyzed and confirmed. An increase in viscosity sustains the kinetic stability of the dense liquid intermediate. Since the distances between ibuprofen molecules within the dense liquid phase are similar to those in the crystal forms, this dense liquid phase is identified as a precursor phase in the nucleation of ibuprofen, in which densification is followed by generation of structural order. This discovery may make it possible to enrich poorly soluble pharmaceuticals beyond classical solubility limitations in aqueous environments. [ABSTRACT FROM AUTHOR]

With the picolinyl (Pic) group as a C‐1 located directing group and N3 as versatile precursor for C5‐NH2, a novel 1‐Pic‐5‐N3 thiosialyl donor was designed and synthesized, based on which a new sialylation protocol was established. In comparison to conventional sialylation methods, the new protocol exhibited obvious advantages, including excellent α‐stereoselectivity in the absence of a solvent effect, broad substrate scope encompassing the challenging sialyl 8‐ and 9‐hydroxy groups of sialic acid acceptors, flexibility in sialoside derivative synthesis, high temperature tolerance and easy scalability. In particular, the applicability to the synthesis of complex and bioactive N‐glycan antennae when combined with the MPEP glycosylation protocol via the "latent‐active" strategy has been shown. Mechanistically, the excellent α‐stereoselectivity of the novel sialylation protocol could be attributed to the dramatic electron‐withdrawing effect of the protonated Pic groups, which was supported by control reactions and DFT calculations. [ABSTRACT FROM AUTHOR]

Small‐ to medium‐sized clusters occur in various areas of chemistry, for example, as active species of heterogeneous catalysis or as transient intermediates during chemical vapor deposition. The manipulation of stable representatives is mostly limited to the stabilizing ligand periphery, virtually excluding the systematic variation of the property‐determining cluster scaffold. We now report the deliberate expansion of a stable unsaturated silicon cluster from six to seven and finally eight vertices. The consecutive application of lithium/naphthalene as the reducing agent and decamethylsilicocene as the electrophilic source of silicon results in the expansion of the core by precisely one atom with the potential of infinite repetition. A stable unsaturated Si6R6 cluster was consecutively expanded to the stable neutral and anionic clusters Si7R6, Si7R5−, and Si8R6. Key to this method is the use of decamethylsilicocene (Cp*2Si) as the electrophile with Cp*− as the leaving group. [ABSTRACT FROM AUTHOR]

Unambiguously confirmed by low‐temperature in situ NMR experiments, X‐ray diffraction and vibrational spectroscopy, phosphonium‐carbenium superelectrophiles are shown to be generated in strong acidic conditions. Representing crucial intermediates, their exploitation allows for the synthesis of unprecedented fluorinated (cyclic) phosphine oxides. Superelectrophile: Phosphonium carbenium dications are formed by the protonation of unsaturated phosphine oxides in superacid. The superelectrophilic character of these dications is essential for the syntheses of various novel fluorinated and cyclic phosphine oxides. [ABSTRACT FROM AUTHOR]

Redox‐active esters (RAEs) as alkyl radical precursors have been extensively developed for C−C bond formations. However, the analogous transformations of fluoroalkyl radicals from the corresponding acid or ester precursors remain challenging because of the high oxidation potential of the fluoroalkyl carboxylate anions. The newly developed N‐hydroxybenzimidoylchloride (NHBC) ester provides a general leaving group assisted strategy to generate a portfolio of fluoroalkyl radicals, and can be successfully applied in photoinduced decarboxylative hydrofluoroalkylation and heteroarylation of unactivated olefins. In addition, DFT calculations revealed that the NHBC ester proceeds by the fluorocarbon radical pathway, whereas other well‐known RAEs proceed by the nitrogen radical pathway. Game of electronics: N‐hydroxybenzimidoyl chloride (NHBC) ester provides a general leaving group assisted strategy to generate a portfolio of fluoroalkyl radicals, and it can be successfully applied in photoinduced decarboxylative hydrofluoroalkylation and heteroarylation of unactivated olefins. The reaction proceeds under mild reaction conditions for both terminal and internal alkenes. [ABSTRACT FROM AUTHOR]

A one‐pot strategy for the diverse construction of a series of supermacrocycles was realized using rationally designed macrocyclic precursors. The base was found to have a significant effect not only on the size distribution but also on the structure of the supermacrocycles formed. While the use of less CsF (<4.0 equiv) afforded regular supermacrocycles containing up to four macrocyclic precursor subunits, the use of more CsF (>8.0 equiv) resulted in structurally reorganized supermacrocyles featuring oxacalix[2]arene[2]triazine motifs. Base‐mediated supermacrocycle‐to‐supermacrocycle transformations were also revealed. With large cavities and many electron‐deficient triazine moieties, the supermacrocyles can accommodate large organic anions via multiple anion–π interactions as demonstrated for two supermacrocycles, which can host 2‐carboxyacetate and represent the first crystallographic examples of sandwich‐like structures with anion–π interactions. A one‐pot strategy for the diversity‐oriented construction of multicavity‐containing supermacrocycles and their interconversion has been developed. With large cavities and multiple electron‐deficient triazines, these supermacrocycles can accommodate large organic anions through unprecedented multiple anion–π interactions. [ABSTRACT FROM AUTHOR]

Based on a terpenoid overproduction platform in yeast for genome mining, a chimeric diterpene synthase from the endophytic fungus Colletotrichum gloeosporioides ES026 was characterized as the (5R,12R,14S)‐dolasta‐1(15),8‐diene synthase. The absolute configuration was independently verified through the use of enantioselectively deuterated terpene precursors, which unequivocally established the predicted C1‐III‐IV cyclization mode for this first characterized clade II‐D enzyme. Extensive isotopic labeling experiments and isolation of the intermediate (1R)‐δ‐araneosene supported the proposed cyclization mechanism. The missing link: Fungal chimeric diterpene synthases with prenyltransferase and terpene synthase domains fall into two clades (I+II) with six subclades (A–F). The present study reports the characterization of the first clade II‐D enzyme, the structures of its products, and the cyclization mechanism. The observed 12R configuration reveals a uniform stereochemistry at this carbon for all clade II enzyme products. [ABSTRACT FROM AUTHOR]

A regioselective, nickel‐catalyzed photoredox allylation of secondary, benzyl, and α‐alkoxy radical precursors is disclosed. Through this manifold, a variety of linear allylic alcohols and allylated monosaccharides are accessible in high yields under mild reaction conditions. Quantum mechanical calculations [DFT and DLPNO‐CCSD(T)] support the mechanistic hypothesis of a Ni0 to NiII oxidative addition pathway followed by radical addition and inner‐sphere allylation. Coming to light: Report herein is a highly regioselective, intermolecular, nickel‐catalyzed photoredox allylic substitution that expands both the radical and electrophile scope of dual photoredox/Ni‐catalyzed reactions. Quantum mechanical calculations shed light on the mechanistic pathway, supporting a Ni0 to NiII oxidative addition followed by an inner‐sphere radical addition. PC=photocatalyst, RP=radical precursor. [ABSTRACT FROM AUTHOR]

We demonstrate a simple method to create a variety of silica‐based colloidal molecules through the covalent assembly of site‐specifically functionalized patchy nanoparticles with complementary nanospheres. Colloidal analogues of BeBr2, BBr3 and CBr4 are obtained from sp‐, sp2‐ and sp3‐like particles, while Br2O and NBr3 analogues can be fabricated by varying the relative amounts of both colloidal precursors. We also show that it is possible to attach covalently silica nanospheres of various sizes to one central patchy nanoparticle, which leads to the formation of more complex colloidal molecules, including chiral ones. The possibility to easily extend the strategy to other colloidal precursors which can serve as satellites, for example, ellipsoidal polymer particles or metallic nanoparticles, opens the way to a rich variety of new colloidal analogues of atoms which could serve as building blocks of next generation materials. Molecular model kit: A large variety of silica‐based colloidal molecules, including chiral ones, has been created through the covalent assembly of site‐specifically functionalized patchy nanoparticles with complementary nanospheres. [ABSTRACT FROM AUTHOR]

While bottom‐up syntheses of ordered nanostructured materials at colloidal length scales have been successful at producing close‐packed materials, it is more challenging to synthesize non‐close‐packed (ncp) structures. Here, a metal oxide nanostructure with ncp hollow sphere arrays was synthesized by combining a polymeric colloidal crystal template (CCT) with a Pechini precursor. The CCT provided defined confinement through its tetrahedral (Td) and octahedral (Oh) voids where the three‐dimensionally (3D) ordered, ncp hollow sphere arrays formed as a result of a crystallization‐induced rearrangement. This nanostructure, consisting of alternating, interconnected large and small hollow spheres, is distinct from the inverse opal structures typically generated from these CCTs. The morphology of the ncp hollow sphere arrays was retained in pseudomorphic transformations involving sulfidation and reoxidation cycling despite the segregation of zinc during these steps. Airy architecture: A new concept for the fabrication of nanostructures featuring 3D ordered, non‐close‐packed hollow sphere arrays is demonstrated through controlling dynamic changes in interfacial properties between template and precursor. The polymeric colloidal crystal provides defined confinement through its tetrahedral and octahedral voids where the arrays are formed as a result of a crystallization‐induced rearrangement. [ABSTRACT FROM AUTHOR]

Carbon aerogels that are typically prepared using sol–gel chemistry have unique three dimensional networks of interconnected nanometer‐sized particles and thus exhibit many fascinating physical properties and great application potentials in widespread fields. To boost the practical applications, it is necessary to develop efficient and low‐cost methods to produce high‐performance carbon aerogels on a large‐scale, preferably in a sustainable way. In 2012, two new classes of aerogels consisting of carbon‐nanofiber (CNF) networks were prepared from biomass‐derived precursors by chemosynthesis (i.e. template‐directed hydrothermal carbonization of carbohydrate) and biosynthesis (i.e. use of bacterial cellulose as precursor), respectively. This Review gives a critical overview of this emerging and rapidly developing field, focusing on the synthetic strategies of the carbon‐nanofiber aerogels and their outstanding physical properties. We also discuss the multifunctional application potentials of the two sorts of carbon aerogels and their nanocomposites, and highlight the challenges and future opportunities in this field. Aero smiths: Carbon aerogels exhibit many fascinating physical properties and great application potentials in widespread fields. This Review covers recent advances in synthetic strategies, physical properties, and multifunctional applications of two emerging carbon‐nanofiber aerogels derived from chemosynthesis and biosynthesis approaches in a comparative perspective. [ABSTRACT FROM AUTHOR]

Abstract: A highly efficient copper‐mediated aromatic pentafluoroethylation method using TMSCF3 as the sole fluoroalkyl source is described. The reaction proceeds by a key C1 to C2 process, that is, the generation of CuCF3 from TMSCF3, followed by a subsequent spontaneous transformation into CuC2F5. Various aryl iodides were pentafluoroethylated with the TMSCF3‐derived CuC2F5. This method represents the first practical and efficient method for pentafluoroethylation of aryl iodides using commercially available TMSCF3 as a pentafluoroethyl precursor. [ABSTRACT FROM AUTHOR]

Abstract: In analogy to the classical reaction of C−B bonds with peroxides, the first oxidative functionalization of aminoboranes through a 1,2‐N migration was realized. Readily available aliphatic nitro compounds are thereby transformed into N‐ and O‐functionalized hydroxylamines in a single synthetic operation. Addition of hazardous peroxides is avoided. Instead, the insertion of O2, as the terminal oxidant, into Zn−C bonds provides the necessary peroxides. The required zinc organyls, in turn, are formed through a boron‐to‐zinc exchange, from an organoboronic ester byproduct of the nitro‐to‐aminoborane transformation. [ABSTRACT FROM AUTHOR]

Abstract: Atomic layer deposition (ALD) of the pyrite‐type metal disulfides FeS2, CoS2, and NiS2 is reported for the first time. The deposition processes use iron, cobalt, and nickel amidinate compounds as the corresponding metal precursors and the H2S plasma as the sulfur source. All the processes are demonstrated to follow ideal self‐limiting ALD growth behavior to produce fairly pure, smooth, well‐crystallized, stoichiometric pyrite FeS2, CoS2, and NiS2 films. By these processes, the FeS2, CoS2, and NiS2 films can also be uniformly and conformally deposited into deep narrow trenches with aspect ratios as high as 10:1, which thereby highlights the broad and promising applicability of these ALD processes for conformal film coatings on complex high‐aspect‐ratio 3D architectures in general. [ABSTRACT FROM AUTHOR]

Abstract: Reactive sulfur species (RSS) are biologically important molecules. Among them, H2S, hydrogen polysulfides (H2Sn,n>1), persulfides (RSSH), and HSNO are believed to play regulatory roles in sulfur‐related redox biology. However, these molecules are unstable and difficult to handle. Having access to their reliable and controllable precursors (or donors) is the prerequisite for the study of these sulfur species. Reported in this work is the preparation and evaluation of a series of O‐silyl‐mercaptan‐based sulfur‐containing molecules which undergo pH‐ or F−‐mediated desilylation to release the corresponding H2S, H2Sn, RSSH, and HSNO in a controlled fashion. This O→S relay deprotection serves as a general strategy for the design of pH‐ or F−‐triggered RSS donors. Moreover, we have demonstrated that the O‐silyl groups in the donors could be changed into other protecting groups like esters. This work should allow the development of RSS donors with other activation mechanisms (such as esterase‐activated donors). [ABSTRACT FROM AUTHOR]

Abstract: Molecular‐level airborne sensing is critical for early prevention of disasters, diseases, and terrorism. Currently, most 2D surface‐enhanced Raman spectroscopy (SERS) substrates used for air sensing have only one functional surface and exhibit poor SERS‐active depth. “Aerosolized plasmonic colloidosomes” (APCs) are introduced as airborne plasmonic hotspots for direct in‐air SERS measurements. APCs function as a macroscale 3D and omnidirectional plasmonic cloud that receives laser irradiation and emits signals in all directions. Importantly, it brings about an effective plasmonic hotspot in a length scale of approximately 2.3 cm, which affords 100‐fold higher tolerance to laser misalignment along the z‐axis compared with 2D SERS substrates. APCs exhibit an extraordinary omnidirectional property and demonstrate consistent SERS performance that is independent of the laser and analyte introductory pathway. Furthermore, the first in‐air SERS detection is demonstrated in stand‐off conditions at a distance of 200 cm, highlighting the applicability of 3D omnidirectional plasmonic clouds for remote airborne sensing in threatening or inaccessible areas. [ABSTRACT FROM AUTHOR]

Abstract: Tetrahydroisoquinolines and tetrahydrobenzazepines were prepared by acid‐promoted ring contraction of cyclic ureas, which were themselves formed by ring expansion of indolines and tetrahydroquinolines. The consequent overall one‐carbon insertion reaction gives these 6‐ and 7‐membered heterocyclic scaffolds in three steps from readily available precursors. Other ring sizes may be formed by an alternative elimination reaction of bicyclic structures. Scalability of the method was demonstrated by operating it in a flow system. [ABSTRACT FROM AUTHOR]

Abstract: Cascade transformations forming multiple bonds and one‐pot procedures provide rapid access to natural‐product‐like scaffolds from simple precursors. These atom‐economic processes are valuable tools in organic synthesis and drug discovery. Herein, we report on ruthenium‐catalyzed cascade annulations of indole with readily available propargyl alcohols. These provide rapid access to diverse carbazoles, cyclohepta[b]indoles, and further fused polycycles with high selectivity. A bifunctional ruthenium complex featuring a redox‐coupled cyclopentadienone ligand acts as a common catalyst for the different cascade processes. [ABSTRACT FROM AUTHOR]

Abstract: Atomic layer deposition (ALD) of the pyrite‐type metal disulfides FeS2, CoS2, and NiS2 is reported for the first time. The deposition processes use iron, cobalt, and nickel amidinate compounds as the corresponding metal precursors and the H2S plasma as the sulfur source. All the processes are demonstrated to follow ideal self‐limiting ALD growth behavior to produce fairly pure, smooth, well‐crystallized, stoichiometric pyrite FeS2, CoS2, and NiS2 films. By these processes, the FeS2, CoS2, and NiS2 films can also be uniformly and conformally deposited into deep narrow trenches with aspect ratios as high as 10:1, which thereby highlights the broad and promising applicability of these ALD processes for conformal film coatings on complex high‐aspect‐ratio 3D architectures in general. [ABSTRACT FROM AUTHOR]

Abstract: A novel strategy to generate functionalized 1‐azatriene intermediates for 6π electrocyclizations was developed by using readily accessible dienyne‐imides and various terminal olefins under PdII catalysis. Taking advantage of the sequential cooperation between preloaded and incorporated functional handles at 1,3‐dien‐5‐yne skeletons, this method not only enables the selective generation of putative 1‐azatrienes but significantly accelerates their thermal 6π‐electrocyclic ring‐closure processes to a series of highly substituted furo[2,3‐b]dihydropyridine derivatives in good yields. [ABSTRACT FROM AUTHOR]

Abstract: In an effort to characterize the electronic states of ethylenedione, OCCO, photoelectron‐photofragment coincidence (PPC) spectroscopy was applied to measure anions at m/z 56 and 57 using a pulsed discharge of glyoxal vapor and N2O. PPC measurements at a photon energy of 3.20 eV yield photoelectron spectra in coincidence with either neutral photofragments or stable neutral products. The measurements showed that primarily stable neutral products were formed, with photoelectron spectra consistent with the oxyallyl diradical, C3H4O, and acetone enolate radical, C3H5O. The spectra were also found to have features nearly identical to those reported for OCCO and HOCCO by Sanov and co‐workers. The stability of the neutral products, as well as an examination of spectra reported for the oxyallyl anion and acetone enolate show that the previous assignments of OCCO and HOCCO are in error, and are instead attributed here to the oxyallyl diradical, C3H4O, and the acetone enolate radical, C3H5O. [ABSTRACT FROM AUTHOR]

Abstract: An efficient annulation involving pyrone addition to a quinone and Dieckmann condensation was developed for rapid assembly of a γ‐naphthopyrone monomeric precursor to the bis‐naphthoquinone natural product aurofusarin. Dimerization was achieved through PdII‐catalyzed dehydrogenative coupling. Further studies employing asymmetric nucleophilic epoxidation indicate that the atropisomers of aurofusarin and derivatives are not configurationally stable at ambient temperature. [ABSTRACT FROM AUTHOR]

Coupling of readily available boronic acids and diazo compounds has emerged recently as a powerful metal-free carbon-carbon bond forming method. However, the difficulty in forming the unstable diazo compound partner in a mild fashion has hitherto limited their general use and the scope of the transformation. Here, we report the application of oxadiazolines as precursors for the generation of an unstable family of diazo compounds using flow UV photolysis and their first use in divergent protodeboronative and oxidative C(sp2)−C(sp3) cross-coupling processes, with excellent functional-group tolerance. [ABSTRACT FROM AUTHOR]

Poly( ortho ester)s (POEs) are well-known for their surface-eroding properties and hence present unique opportunities for controlled-release and tissue-engineering applications. Their development and wide-spread investigation has, however, been severely limited by challenging synthetic requirements that incorporate unstable intermediates and are therefore highly irreproducible. Herein, the first catalytic method for the synthesis of POEs using air- and moisture-stable vinyl acetal precursors is presented. The synthesis of a range of POE structures is demonstrated, including those that are extremely difficult to achieve by other synthetic methods. Furthermore, application of this chemistry permits efficient installation of functional groups through ortho ester linkages on an aliphatic polycarbonate. [ABSTRACT FROM AUTHOR]

The direct observation of amorphous barium carbonate (ABC), which transforms into a previously unknown barium carbonate hydrate (herewith named gortatowskite) within a few hundred milliseconds of formation, is described. In situ X-ray scattering, cryo-, and low-dose electron microscopy were used to capture the transformation of nanoparticulate ABC into gortatowskite crystals, highly anisotropic sheets that are up to 1 μm in width, yet only about 10 nm in thickness. Recrystallization of gortatowskite to witherite starts within 30 seconds. We describe a bulk synthesis and report a first assessment of the composition, vibrational spectra, and structure of gortatowskite. Our findings indicate that transient amorphous and crystalline precursors can play a role in aqueous precipitation pathways that may often be overlooked owing to their extremely short lifetimes and small dimensions. However, such transient precursors may be integral to the formation of more stable phases. [ABSTRACT FROM AUTHOR]

Reduction of indium boryl precursors to give two- and three-dimensional M−M bonded networks is influenced by the choice of supporting ligand. While the unprecedented nanoscale cluster [In68(boryl)12]− (with an In12@In44@In12(boryl)12 concentric structure), can be isolated from the potassium reduction of a bis(boryl)indium(III) chloride precursor, analogous reduction of the corresponding (benzamidinate)InIIIBr(boryl) system gives a near-planar (and weakly aromatic) tetranuclear [In4(boryl)4]2− system. [ABSTRACT FROM AUTHOR]

Three tetrahedral organic cages have been obtained by condensing a triamino linker with a set of three ostensibly analogous triformyl precursors. Despite the large number of imine bonds formed, the corresponding cages were obtained in exceptionally high yields. Both theory and experimental results demonstrate that intramolecular CH⋅⋅⋅π interactions within all of the cage frameworks play an important role in abetting the condensations and contributing to the near-quantitative synthetic yields. The three cages of this study exhibit high thermodynamic and kinetic stability. A variety of small neutral guest molecules with complementary sizes and geometries may be used as templates in the cage forming reactions. Among the guests that may be used in this way is white phosphorus (P4), whose inherent reactivity towards oxygen is almost fully attenuated when bound within one of the cages. [ABSTRACT FROM AUTHOR]

Tri(pyrazolyl)phosphanes ( 5R1,R2) are utilized as an alternative, cheap and low-toxic phosphorus source for the convenient synthesis of InP/ZnS quantum dots (QDs). From these precursors, remarkably long-term stable stock solutions (>6 months) of P(OLA)3 (OLAH=oleylamine) are generated from which the respective pyrazoles are conveniently recovered. P(OLA)3 acts simultaneously as phosphorus source and reducing agent in the synthesis of highly emitting InP/ZnS core/shell QDs. These QDs are characterized by a spectral range between 530-620 nm and photoluminescence quantum yields (PL QYs) between 51-62 %. A proof-of-concept white light-emitting diode (LED) applying the InP/ZnS QDs as a color-conversion layer was built to demonstrate their applicability and processibility. [ABSTRACT FROM AUTHOR]

Intramolecular aryl-aryl coupling is the key transformation in the rational synthesis of nanographenes and nanoribbons. In this respect the C−F bond activation was shown to be a versatile alternative enabling the synthesis of several unique carbon-based nanostructures. Herein we describe an unprecedentedly challenging transformation showing that the C−F bond activation by aluminum oxide allows highly effective domino-like C−C bond formation. Despite the flexible nature of oligophenylene-based precursors efficient regioselective zipping to the target nanostructures was achieved. We show that fluorine positions in the precursor structure unambiguously dictate the 'running of the zipping-program' which results in rolling-up of linear oligophenylene chains around phenyl moieties yielding target nanographenes. The high efficiency of zipping makes this approach attractive for the synthesis of unsubstituted nanographenes which are difficult to obtain in pure form by other methods. [ABSTRACT FROM AUTHOR]

Rare-earth metal complexes (Flu-CH2-Py)Ln(CH2SiMe3)2(THF) n (Ln=Sc( 1), Lu( 2), Tm( 3), Y( 4) and Gd( 5)), upon the activation of [Ph3C][B(C6F5)4] and Al iBu3, were employed to catalyze the polymerization of allene derivatives under mild conditions. The Gd, Y, Tm, Lu metal based precursors exhibited distinguished 2,3-selectivity (>99.9 %) for phenylallene (PA) polymerization, whereas the smallest Sc metal based precursor showed a moderate 2,3-selectivity. The activity increased with the central metal size following the trend of Gd( 5)>Tm( 4)>Y( 3)>Lu( 2)>Sc( 1). Moreover, Gd( 5) also realized the purely 2,3-selective polymerizations of polar or nonpolar allene derivatives, para-methylphenylallene, para-flourophenylallene and para-methoxyphenylallene, regardless of electron-donating or -withdrawing substituents. Owing to the highly regular backbones, these polymers (except PPA) were crystalline, thus being the first crystalline polymers based on allene derivatives. [ABSTRACT FROM AUTHOR]

Herein a convenient synthetic method to obtain 2,2,3,3-tetrasilyltetrasilane 3 and 2,2,3,3,4,4-hexasilylpentasilane 4 on a multigram scale is presented. Proton-coupled 29Si NMR spectroscopy and single-crystal X-ray crystallography enabled unequivocal structural assignment. Owing to their unique properties, which are reflected in their nonpyrophoric character on contact with air and their enhanced light absorption above 250 nm, 3 and 4 are valuable precursors for liquid-phase deposition (LPD) and the processing of thin silicon films. Amorphous silicon (a-Si:H) films of excellent quality were deposited starting from 3 and characterized by conductivity measurements, ellipsometry, optical microscopy, and Raman spectroscopy. [ABSTRACT FROM AUTHOR]

The colloidal synthesis and assembly of semiconductor nanowires continues to attract a great deal of interest. Herein, we describe the single-step ligand-mediated synthesis of single-crystalline CsPbBr3 perovskite nanowires (NWs) directly from the precursor powders. Studies of the reaction process and the morphological evolution revealed that the initially formed CsPbBr3 nanocubes are transformed into NWs through an oriented-attachment mechanism. The optical properties of the NWs can be tuned across the entire visible range by varying the halide (Cl, Br, and I) composition through subsequent halide ion exchange. Single-particle studies showed that these NWs exhibit strongly polarized emission with a polarization anisotropy of 0.36. More importantly, the NWs can self-assemble in a quasi-oriented fashion at an air/liquid interface. This process should also be easily applicable to perovskite nanocrystals of different morphologies for their integration into nanoscale optoelectronic devices. [ABSTRACT FROM AUTHOR]

Uniform Ni3C nanodots dispersed in ultrathin N-doped carbon nanosheets were successfully prepared by carburization of the two dimensional (2D) nickel cyanide coordination polymer precursors. The Ni3C based nanosheets have lateral length of about 200 nm and thickness of 10 nm. When doped with Fe, the Ni3C based nanosheets exhibited outstanding electrocatalytic properties for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). For example, 2 at % Fe (atomic percent) doped Ni3C nanosheets depict a low overpotential (292 mV) and a small Tafel slope (41.3 mV dec−1) for HER in KOH solution. An outstanding OER catalytic property is also achieved with a low overpotential of 275 mV and a small Tafel slope of 62 mV dec−1 in KOH solution. Such nanodot-incorporated 2D hybrid structures can serve as an efficient bifunctional electrocatalyst for overall water splitting. [ABSTRACT FROM AUTHOR]

The imidazolium chloride [C3H3N(C3H6NMe2)N{C(Me)(=NDipp)}]Cl ( 1; Dipp=2,6-diisopropyl phenyl), a potential precursor to a tritopic NimineCNHCNamine pincer-type ligand, reacted with [Ni(cod)2] to give the NiI-NiI complex 2, which contains a rare cod-derived η3-allyl-type bridging ligand. The implied intermediate formation of a nickel hydride through oxidative addition of the imidazolium C−H bond did not occur with the symmetrical imidazolium chloride [C3H3N2{C(Me)(=NDipp)}2]Cl ( 3). Instead, a Ni−C(sp3) bond was formed, leading to the neutral NimineCHNimine pincer-type complex Ni[C3H3N2{C(Me)(=NDipp)}2]Cl ( 4). Theoretical studies showed that this highly unusual feature in nickel NHC chemistry is due to steric constraints induced by the N substituents, which prevent Ni−H bond formation. Remarkably, ethylene inserted into the C(sp3)−H bond of 4 without nickel hydride formation, thus suggesting new pathways for the alkylation of non-activated C−H bonds. [ABSTRACT FROM AUTHOR]

The Robinson annulation is a reaction that has been useful for numerous syntheses since its discovery in 1935, especially in the field of steroid synthesis. The products are usually obtained after three consecutive steps: the formation of an enolate (or derivative), a conjugate addition, and an aldol reaction. Over the years, several methodological improvements have been made for each individual step or alternative routes have been devised to access the Robinson annulation products. The first part of this Review outlines the most relevant developments towards the formation of monocarbonyl-derived Robinson annulation products (MRA products, MRAPs) and activated monocarbonyl-derived Robinson annulation products (AMRA products, AMRAPs). The following sections are then devoted to the diastereoselective and enantioselective synthesis of these products, while the last section describes the enantiomeric resolution of racemic mixtures. [ABSTRACT FROM AUTHOR]

Nanostructured metal sulfide-amine hybrid materials have attracted attention because of their unique properties and versatility as precursors for functional inorganic nanomaterials. However, large-scale synthesis of metal sulfide-amine hybrid nanomaterials is limited by hydrothermal and solvothermal preparative reaction conditions; consequently, incorporation of such materials into functional nanomaterials is hindered. An amine molecule-assisted refluxing method was used to synthesize highly uniform zinc sulfide⋅(diethylenetriamine)0.5 (ZnS⋅(DETA)0.5) hybrid nanosheets and nanobelts in a large scale. The obtained ZnS⋅(DETA)0.5 hybrid nanomaterials can be used as efficient precursors to fabricate functional ZnS nanomaterials and carbon encapsulated sulfur (S@C) nanocomposite cathodes for Li-S batteries. [ABSTRACT FROM AUTHOR]

Acenes are intriguing molecules with unique electronic properties. The difficulties in their preparation owing to low stability under ambient conditions are apparent because successful syntheses of long unsubstituted acenes are still scarce, in spite of the great attention they have attracted. Only unsubstituted acenes up to heptacene have been isolated in bulk, with nonacene being the largest acene detected to date. Herein we use on-surface assisted reduction of tetraepoxy decacene precursors on Au(111) as the key step to generate unprecedented decacene which is visualized and its electronic resonances studied by scanning tunneling microscopy (STM) and spectroscopy (STS). [ABSTRACT FROM AUTHOR]

We have developed a strategy to transform olefins into homoallylic nitriles through a mechanism that combines copper catalysis with alkyl nitrile radicals. The radicals are easily generated from alkyl nitriles in the presence of the mild oxidant di- tert-butyl peroxide. This cross-dehydrogenative coupling between simple olefins and alkylnitriles bears advantages over the conventional use of halides and toxic cyanide reagents. With this method, we showcase the facile synthesis of a flavoring agent, a natural product, and a polymer precursor from simple olefins. [ABSTRACT FROM AUTHOR]