TL;DR: The ability to design COFs and to adjust their pore metrics using the principles of reticular synthesis has given rise to frameworks with ultralow densities, which has resulted in the first implementation of the concept of molecular weaving.
Abstract: Just over a century ago, Lewis published his seminal work on what became known as the covalent bond, which has since occupied a central role in the theory of making organic molecules. With the advent of covalent organic frameworks (COFs), the chemistry of the covalent bond was extended to two- and three-dimensional frameworks. Here, organic molecules are linked by covalent bonds to yield crystalline, porous COFs from light elements (boron, carbon, nitrogen, oxygen, and silicon) that are characterized by high architectural and chemical robustness. This discovery paved the way for carrying out chemistry on frameworks without losing their porosity or crystallinity, and in turn achieving designed properties in materials. The recent union of the covalent and the mechanical bond in the COF provides the opportunity for making woven structures that incorporate flexibility and dynamics into frameworks.
TL;DR: This review focuses on the likely mechanisms of action of ruthenium(ii)-based anticancer drugs and the relationship between their chemical structures and biological properties, and highlights the catalytic activity and the photoinduced activation of r Ruthenium (ii) complexes, their targeted delivery, and their activity in nanomaterial systems.
Abstract: Cancer is rapidly becoming the top killer in the world. Most of the FDA approved anticancer drugs are organic molecules, while metallodrugs are very scarce. The advent of the first metal based therapeutic agent, cisplatin, launched a new era in the application of transition metal complexes for therapeutic design. Due to their unique and versatile biochemical properties, ruthenium-based compounds have emerged as promising anti-cancer agents that serve as alternatives to cisplatin and its derivertives. Ruthenium(iii) complexes have successfully been used in clinical research and their mechanisms of anticancer action have been reported in large volumes over the past few decades. Ruthenium(ii) complexes have also attracted significant attention as anticancer candidates; however, only a few of them have been reported comprehensively. In this review, we discuss the development of ruthenium(ii) complexes as anticancer candidates and biocatalysts, including arene ruthenium complexes, polypyridyl ruthenium complexes, and ruthenium nanomaterial complexes. This review focuses on the likely mechanisms of action of ruthenium(ii)-based anticancer drugs and the relationship between their chemical structures and biological properties. This review also highlights the catalytic activity and the photoinduced activation of ruthenium(ii) complexes, their targeted delivery, and their activity in nanomaterial systems.
TL;DR: A machine-learning model, based on a local description of chemical environments and Bayesian statistical learning, provides a unified framework to predict atomic-scale properties and captures the quantum mechanical effects governing the complex surface reconstructions of silicon.
Abstract: Determining the stability of molecules and condensed phases is the cornerstone of atomistic modeling, underpinning our understanding of chemical and materials properties and transformations We show that a machine-learning model, based on a local description of chemical environments and Bayesian statistical learning, provides a unified framework to predict atomic-scale properties It captures the quantum mechanical effects governing the complex surface reconstructions of silicon, predicts the stability of different classes of molecules with chemical accuracy, and distinguishes active and inactive protein ligands with more than 99% reliability The universality and the systematic nature of our framework provide new insight into the potential energy surface of materials and molecules
TL;DR: A versatile modulator-induced defect-formation strategy is developed, in the presence of monocarboxylic acid as a modulator and an insufficient amount of organic ligand, successfully realizing the controllable synthesis of hierarchically porous MOFs (HP-MOFs) with high stability and tailorable pore characters.
Abstract: The pore size enlargement and structural stability have been recognized as two crucial targets, which are rarely achieved together, in the development of metal–organic frameworks (MOFs). Herein, we have developed a versatile modulator-induced defect-formation strategy, in the presence of monocarboxylic acid as a modulator and an insufficient amount of organic ligand, successfully realizing the controllable synthesis of hierarchically porous MOFs (HP-MOFs) with high stability and tailorable pore characters. Remarkably, the integration of high stability and large mesoporous property enables these HP-MOFs to be important porous platforms for applications involving large molecules, especially in catalysis.
TL;DR: This work reports ion transport through ultimately narrow slits that are fabricated by effectively removing a single atomic plane from a bulk crystal, and finds that ions with hydrated diameters larger than the slit size can still permeate through, albeit with reduced mobility.
Abstract: In the field of nanofluidics, it has been an ultimate but seemingly distant goal to controllably fabricate capillaries with dimensions approaching the size of small ions and water molecules. We report ion transport through ultimately narrow slits that are fabricated by effectively removing a single atomic plane from a bulk crystal. The atomically flat angstrom-scale slits exhibit little surface charge, allowing elucidation of the role of steric effects. We find that ions with hydrated diameters larger than the slit size can still permeate through, albeit with reduced mobility. The confinement also leads to a notable asymmetry between anions and cations of the same diameter. Our results provide a platform for studying the effects of angstrom-scale confinement, which is important for the development of nanofluidics, molecular separation, and other nanoscale technologies.
TL;DR: Observation of a network of interchain interactions, as established by NOE spectroscopy, shows the importance of Phe and Arg interactions in driving the phase separation of Ddx4, while the salt dependence of both low- and high-concentration regions of phase diagrams establishes an important role for electrostatic interactions.
Abstract: Membrane encapsulation is frequently used by the cell to sequester biomolecules and compartmentalize their function. Cells also concentrate molecules into phase-separated protein or protein/nucleic acid "membraneless organelles" that regulate a host of biochemical processes. Here, we use solution NMR spectroscopy to study phase-separated droplets formed from the intrinsically disordered N-terminal 236 residues of the germ-granule protein Ddx4. We show that the protein within the concentrated phase of phase-separated Ddx4, [Formula: see text], diffuses as a particle of 600-nm hydrodynamic radius dissolved in water. However, NMR spectra reveal sharp resonances with chemical shifts showing [Formula: see text] to be intrinsically disordered. Spin relaxation measurements indicate that the backbone amides of [Formula: see text] have significant mobility, explaining why high-resolution spectra are observed, but motion is reduced compared with an equivalently concentrated nonphase-separating control. Observation of a network of interchain interactions, as established by NOE spectroscopy, shows the importance of Phe and Arg interactions in driving the phase separation of Ddx4, while the salt dependence of both low- and high-concentration regions of phase diagrams establishes an important role for electrostatic interactions. The diffusion of a series of small probes and the compact but disordered 4E binding protein 2 (4E-BP2) protein in [Formula: see text] are explained by an excluded volume effect, similar to that found for globular protein solvents. No changes in structural propensities of 4E-BP2 dissolved in [Formula: see text] are observed, while changes to DNA and RNA molecules have been reported, highlighting the diverse roles that proteinaceous solvents play in dictating the properties of dissolved solutes.
TL;DR: In this article, the authors developed a comprehensive method to compute bond orders and the sum of bond orders for each atom across various bonding types: metallic, covalent, polar-covalent ionic, aromatic, dative, hypercoordinate, electron deficient multi-centered, agostic, and hydrogen bonding.
Abstract: Developing a comprehensive method to compute bond orders is a problem that has eluded chemists since Lewis's pioneering work on chemical bonding a century ago. Here, a computationally efficient method solving this problem is introduced and demonstrated for diverse materials including elements from each chemical group and period. The method is applied to non-magnetic, collinear magnetic, and non-collinear magnetic materials with localized or delocalized bonding electrons. Examples studied include the stretched O2 molecule, 26 diatomic molecules, 3d and 5d transition metal solids, periodic materials with 1 to 8748 atoms per unit cell, a biomolecule, a hypercoordinate molecule, an electron deficient molecule, hydrogen bound systems, transition states, Lewis acid–base complexes, aromatic compounds, magnetic systems, ionic materials, dispersion bound systems, nanostructures, and other materials. From near-zero to high-order bonds were studied. Both the bond orders and the sum of bond orders for each atom are accurate across various bonding types: metallic, covalent, polar-covalent, ionic, aromatic, dative, hypercoordinate, electron deficient multi-centered, agostic, and hydrogen bonding. The method yields similar results for correlated wavefunction and density functional theory inputs and for different SZ values of a spin multiplet. The method requires only the electron and spin magnetization density distributions as input and has a computational cost scaling linearly with increasing number of atoms in the unit cell. No prior approach is as general. The method does not apply to electrides, highly time-dependent states, some extremely high-energy excited states, and nuclear reactions.
TL;DR: Five metal pentazolate hydrate complexes are synthesized and characterized that exhibit good thermal stability with onset decomposition temperatures greater than 100 °C and the N5− ion can coordinate to the metal cation through either ionic or covalent interactions, and is stabilized through hydrogen-bonding interactions with water.
Abstract: Metal complexes of the pentazole anion exhibit multiple coordination modes, through ionic, covalent and hydrogen-bonding interactions, and good thermal stability with onset decomposition temperatures greater than 100 °C. Polynitrogen compounds can decompose to N2 with an extraordinarily large energy release, which makes them promising candidate materials for explosives but difficult to produce in a stable form. Compounds containing five-membered all-nitrogen rings have attracted particular interest in the search for a stable polynitrogen molecule. Yuangang Xu et al. report five metal complexes containing the pentazole anion, cyclo--N5−, four of which exhibit good thermal stability and a range of different bonding interactions for stabilization. Given their energetic properties and stability, and the adaptability of the cyclo-N5− species in terms of its bonding interactions, these complexes might lead to the development of a new class of high-energy-density materials and of other unusual polynitrogen complexes. Singly or doubly bonded polynitrogen compounds can decompose to dinitrogen (N2) with an extremely large energy release. This makes them attractive as potential explosives or propellants1,2,3, but also challenging to produce in a stable form. Polynitrogen materials containing nitrogen as the only element exist in the form of high-pressure polymeric phases4,5,6, but under ambient conditions even metastability is realized only in the presence of other elements that provide stabilization. An early example is the molecule phenylpentazole, with a five-membered all-nitrogen ring, which was first reported in the 1900s7 and characterized in the 1950s8,9. Salts containing the azide anion (N3−)10,11,12 or pentazenium cation (N5+)13 are also known, with compounds containing the pentazole anion, cyclo-N5−, a more recent addition14,15,16. Very recently, a bulk material containing this species was reported17 and then used to prepare the first example of a solid-state metal–N5 complex18. Here we report the synthesis and characterization of five metal pentazolate hydrate complexes [Na(H2O)(N5)]·2H2O, [M(H2O)4(N5)2]·4H2O (M = Mn, Fe and Co) and [Mg(H2O)6(N5)2]·4H2O that, with the exception of the Co complex, exhibit good thermal stability with onset decomposition temperatures greater than 100 °C. For this series we find that the N5− ion can coordinate to the metal cation through either ionic or covalent interactions, and is stabilized through hydrogen-bonding interactions with water. Given their energetic properties and stability, pentazole–metal complexes might potentially serve as a new class of high-energy density materials19 or enable the development of such materials containing only nitrogen20,21,22,23. We also anticipate that the adaptability of the N5− ion in terms of its bonding interactions will enable the exploration of inorganic nitrogen analogues of metallocenes24 and other unusual polynitrogen complexes.
TL;DR: In this article, a cross-coupling of organosilicon reagents with organic halides or pseudohalides has been considered to be a useful tool for constructing the carbon frameworks of various target molecules such as pharmaceuticals and π-conjugated functional materials.
Abstract: Organosilicon compounds act as a nucleophile upon activation by an appropriate base and behave in a manner similar to main-group organometallic reagents. In the last decades, structurally divergent organosilicon reagents are available and have become more employed for synthetic transformation with the aid of transition-metal complexes, because organosilicon compounds are in general superior to other organometallic compounds in view of stability, solubility, nontoxicity, and easy-handling. Particularly, cross-coupling of organosilicon reagents with organic halides or pseudohalides has been considered to be a useful tool for constructing the carbon frameworks of various target molecules such as pharmaceuticals and π-conjugated functional materials. Perfluoroalkylsilicon compounds such as CF3SiEt3 have found use as reagents for the metal-catalyzed introduction of perfluoroalkyl groups into many substrates. In addition, functionalized organosilicon reagents are readily accessible by catalytic approach startin...
TL;DR: The authors' experimental results confirm that oleylammonium ions act as capping ligands by substituting Cs+ ions from the surface of CsPbBr3 NCs, and DFT calculations shows that the substitution mechanism does not require much energy for surface reconstruction and stabilizes the nanocrystal by the formation of three hydrogen bonds.
Abstract: Optoelectronic properties of CsPbBr3 perovskite nanocubes (NCs) depend strongly on the interaction of the organic passivating molecules with the inorganic crystal. To understand this interaction, we employed a combination of synchrotron-based X-ray photoelectron spectroscopy (XPS), nuclear magnetic resonance (NMR) spectroscopy, and first-principles density functional theory (DFT)-based calculations. Variable energy XPS elucidated the internal structure of the inorganic part in a layer-by-layer fashion, whereas NMR characterized the organic ligands. Our experimental results confirm that oleylammonium ions act as capping ligands by substituting Cs+ ions from the surface of CsPbBr3 NCs. DFT calculations shows that the substitution mechanism does not require much energy for surface reconstruction and, in contrast, stabilizes the nanocrystal by the formation of three hydrogen bonds between the −NH3+ moiety of oleylammonium and surrounding Br– on the surface of NCs. This substitution mechanism and its origin ar...
TL;DR: In this paper, a method employing MOFs as templates to hold guest nanoparticles in their channels and an encapsulation of pre-synthesized nanoparticles was proposed to obtain nanoparticle/MOF composites, which possess the advantages of both parent materials.
Abstract: Over the last twenty years, MOFs have emerged as a new promising porous material in the areas of gas sorption and separation, catalysis, drug delivery, and molecule sensing. Moreover, nanomaterials have also attracted widespread attention in recent years. Owing to the porous structure of MOFs, we can combine nanoparticles with MOFs to obtain nanoparticle/MOF composites, which possess the advantages of both parent materials. In the present study, we utilized two main methods to introduce nanoparticles into MOFs: a method employing MOFs as templates to hold guest nanoparticles in their channels and a method employing the encapsulation of pre-synthesized nanoparticles. The former includes chemical vapor deposition, solid grinding, liquid impregnation, and double solvent methods, and the latter comprises some new techniques such as the self-sacrificing template technique. Herein, we also reviewed their applications in hydrogen storage, ammonia adsorption, acidic gas adsorption, catalytic processes, and energy storage.
TL;DR: It is shown that TERS can chemically and spatially probe the site-specific chemical and physical properties of an atomically well-defined Pd(sub-monolayer)/Au(111) bimetallic model catalyst at 3 nm resolution in real space using phenyl isocyanide as a probe molecule.
Abstract: Tip-enhanced Raman spectroscopy in conjunction with scanning tunnelling microscopy can be used to correlate chemical properties and surface topography of bimetallic catalysts with high spatial resolution. An atomic- and molecular-level understanding of heterogeneous catalysis is required to characterize the nature of active sites and improve the rational design of catalysts1,2,3. Achieving this level of characterization requires techniques that can correlate catalytic performances to specific surface structures, so as to avoid averaging effects1. Tip-enhanced Raman spectroscopy4,5,6,7 combines scanning probe microscopy with plasmon-enhanced Raman scattering and provides simultaneous topographical and chemical information at the nano/atomic scale from ambient8,9,10 to ultrahigh-vacuum11,12 and electrochemical environments13,14. Therefore, it has been used to monitor catalytic reactions15,16,17,18 and is proposed to correlate the local structure and function of heterogeneous catalysts19. Bimetallic catalysts, such as Pd–Au, show superior performance in various catalytic reactions20,21, but it has remained challenging to correlate structure and reactivity because of their structural complexity. Here, we show that TERS can chemically and spatially probe the site-specific chemical (electronic and catalytic) and physical (plasmonic) properties of an atomically well-defined Pd(sub-monolayer)/Au(111) bimetallic model catalyst at 3 nm resolution in real space using phenyl isocyanide as a probe molecule (
Fig. 1a
). We observe a weakened N≡C bond and enhanced reactivity of phenyl isocyanide adsorbed at the Pd step edge compared with that at the Pd terrace. Density functional theory corroborates these observations by revealing a higher d-band electronic profile for the low-coordinated Pd step edge atoms. The 3 nm spatial resolution we demonstrate here is the result of an enhanced electric field and distinct electronic properties at the step edges.
TL;DR: In this article, an enzyme maintains its biological function under a wider range of conditions after being embedded in metal-organic framework (MOF) microcrystals via a de novo approach.
Abstract: We show that an enzyme maintains its biological function under a wider range of conditions after being embedded in metal–organic framework (MOF) microcrystals via a de novo approach. This enhanced stability arises from confinement of the enzyme molecules in the mesoporous cavities in the MOFs, which reduces the structural mobility of enzyme molecules. We embedded catalase (CAT) into zeolitic imidazolate frameworks (ZIF-90 and ZIF-8), and then exposed both embedded CAT and free CAT to a denature reagent (i.e., urea) and high temperatures (i.e., 80 °C). The embedded CAT maintains its biological function in the decomposition of hydrogen peroxide even when exposed to 6 M urea and 80 °C, with apparent rate constants kobs (s–1) of 1.30 × 10–3 and 1.05 × 10–3, respectively, while free CAT shows undetectable activity. A fluorescence spectroscopy study shows that the structural conformation of the embedded CAT changes less under these denaturing conditions than free CAT.
TL;DR: Single crystal structure reveals that imidazole molecules in Im-Cu@(NENU-3a) isolate lattice water molecules and then block proton transport pathway, whereas high concentration of free imidAZole molecules within Im@ (NENu-3) significantly facilitate successive proton-hopping pathways through formation of hydrogen bonded networks.
Abstract: A one-step straightforward strategy has been developed to incorporate free imidazole molecules into a highly stable metal-organic framework (NENU-3, ([Cu12(BTC)8(H2O)12][HPW12O40])·Guest). The resulting material Im@(NENU-3) exhibits a very high proton conductivity of 1.82 × 10-2 S cm-1 at 90% RH and 70 °C, which is significantly higher than 3.16 × 10-4 S cm-1 for Im-Cu@(NENU-3a) synthesized through a two-step approach with mainly terminal bound imidazole molecules inside pores. Single crystal structure reveals that imidazole molecules in Im-Cu@(NENU-3a) isolate lattice water molecules and then block proton transport pathway, whereas high concentration of free imidazole molecules within Im@(NENU-3) significantly facilitate successive proton-hopping pathways through formation of hydrogen bonded networks.
TL;DR: By developing amorphous ZnO nanocages (a-ZnO NCs), this is the first time such remarkable SERS activity has been observed within amorphously semiconductor nanomaterials, which could open a new frontier for developing highly sensitive and stable SERS technology.
Abstract: Enhancement of the semiconductor-molecule interaction, in particular, promoting the interfacial charge transfer process (ICTP), is key to improving the sensitivity of semiconductor-based surface enhanced Raman scattering (SERS). Herein, by developing amorphous ZnO nanocages (a-ZnO NCs), we successfully obtained an ultrahigh enhancement factor of up to 6.62×105 . This remarkable SERS sensitivity can be attributed to high-efficiency ICTP within a-ZnO NC molecule system, which is caused by metastable electronic states of a-ZnO NCs. First-principles density functional theory (DFT) simulations further confirmed a stronger ICTP in a-ZnO NCs than in their crystalline counterparts. The efficient ICTP can even generate π bonding in Zn-S bonds peculiar to the mercapto molecule adsorbed a-ZnO NCs, which has been verified through the X-ray absorption near-edge structure (XANES) characterization. To the best of our knowledge, this is the first time such remarkable SERS activity has been observed within amorphous semiconductor nanomaterials, which could open a new frontier for developing highly sensitive and stable SERS technology.
TL;DR: This work reports the use of a chiral Cu(II) 3D metal-organic framework (MOF) based on the tripeptide Gly-l-His-Gly (GHG) for the enantioselective separation of metamphetamine and ephedrine, the first example of a MOF capable of separating chiral polar drugs.
Abstract: We report the use of a chiral Cu(II) 3D metal–organic framework (MOF) based on the tripeptide Gly-l-His-Gly (GHG) for the enantioselective separation of metamphetamine and ephedrine. Monte Carlo simulations suggest that chiral recognition is linked to preferential binding of one of the enantiomers as a result of either stronger or additional H-bonds with the framework that lead to energetically more stable diastereomeric adducts. Solid-phase extraction of a racemic mixture by using Cu(GHG) as the extractive phase permits isolating >50% of the (+)-ephedrine enantiomer as target compound in only 4 min. To our knowledge, this represents the first example of a MOF capable of separating chiral polar drugs.
TL;DR: The mechanisms of starch oxidation with different oxidizing agents, including sodium hypochlorite, hydrogen peroxide, ozone and sodium periodate, are described in this review and this information may facilitate the development of novel oxidized starches for both food and non-food applications.
TL;DR: This study introduces the red-, green-, and blue-emitting dyes into a MOF together for the first time, producing white-light materials with nearly ideal Commission International ed'Eclairage coordinates, high color-rendering index values, and quantum yields.
Abstract: The unique features of the metal-organic frameworks (MOFs), including ultrahigh porosities and surface areas, tunable pores, endow the MOFs with special utilizations as host matrices. In this work, various neutral and ionic guest dye molecules, such as fluorescent brighteners, coumarin derivatives, 4-(dicyanomethylene)-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran (DCM), and 4-(p-dimethylaminostyryl)-1-methylpyridinium (DSM), are encapsulated in a neutral MOF, yielding novel blue-, green-, and red-phosphors, respectively. Furthermore, this study introduces the red-, green-, and blue-emitting dyes into a MOF together for the first time, producing white-light materials with nearly ideal Commission International ed'Eclairage (CIE) coordinates, high color-rendering index values (up to 92%) and quantum yields (up to 26%), and moderate correlated color temperature values. The white light is tunable by changing the content or type of the three dye guests, or the excitation wavelength. Significantly, the introduction of blue-emitting guests in the methodology makes the available MOF host more extensive, and the final white-light output more tunable and high-quality. Such strategy can be widely adopted to design and prepare white-light-emitting materials.
TL;DR: A new emitter, composed of azatriangulene and diphenyltriazine moieties, is theoretically designed, which is coplanar due to intramolecular H-bonding interactions, and its preliminary photophysical characterizations point to HMAT-TRZ as a potential efficient TADF emitter.
Abstract: In the traditional molecular design of thermally activated delayed fluorescence (TADF) emitters composed of electron-donor and electron-acceptor moieties, achieving a small singlet-triplet energy gap (ΔEST ) in strongly twisted structures usually translates into a small fluorescence oscillator strength, which can significantly decrease the emission quantum yield and limit efficiency in organic light-emitting diode devices. Here, based on the results of quantum-chemical calculations on TADF emitters composed of carbazole donor and 2,4,6-triphenyl-1,3,5-triazine acceptor moieties, a new strategy is proposed for the molecular design of efficient TADF emitters that combine a small ΔEST with a large fluorescence oscillator strength. Since this strategy goes beyond the traditional framework of structurally twisted, charge-transfer type emitters, importantly, it opens the way for coplanar molecules to be efficient TADF emitters. Here, a new emitter, composed of azatriangulene and diphenyltriazine moieties, is theoretically designed, which is coplanar due to intramolecular H-bonding interactions. The synthesis of this hexamethylazatriangulene-triazine (HMAT-TRZ) emitter and its preliminary photophysical characterizations point to HMAT-TRZ as a potential efficient TADF emitter.
TL;DR: A many-body tensor representation that is invariant to translations, rotations and nuclear permutations of same elements, unique, differentiable, can represent molecules and crystals, and is fast to compute is introduced.
Abstract: Accurate simulations of atomistic systems from first principles are limited by computational cost. In high-throughput settings, machine learning can potentially reduce these costs significantly by accurately interpolating between reference calculations. For this, kernel learning approaches crucially require a single Hilbert space accommodating arbitrary atomistic systems. We introduce a many-body tensor representation that is invariant to translations, rotations and nuclear permutations of same elements, unique, differentiable, can represent molecules and crystals, and is fast to compute. Empirical evidence is presented for energy prediction errors below 1 kcal/mol for 7k organic molecules and 5 meV/atom for 11k elpasolite crystals. Applicability is demonstrated for phase diagrams of Pt-group/transition-metal binary systems.
TL;DR: The terms tetrel bond, pnictogen bond and chalcogen bond were coined recently to describe non-covalent interactions involving group 14, 15 and 16 atoms, respectively, acting as the electrophilic site that seeks a nucleophilic region of another molecule, for example a non-bonding electron pair or π-electron pair of a Lewis base.
Abstract: The terms tetrel bond, pnictogen bond and chalcogen bond were coined recently to describe non-covalent interactions involving group 14, 15 and 16 atoms, respectively, acting as the electrophilic site that seeks a nucleophilic region of another molecule, for example a non-bonding electron pair or π-electron pair of a Lewis base Many complexes containing these non-covalent bonds were identified and characterised in isolation in the gas phase by rotational and vibrational spectroscopy long before they were given these names In this article, the geometries so determined for selected examples of complexes of each type are rationalised in terms of the molecular electrostatic surface potentials of the component molecules Examples of chalcogen-bonded complexes considered are based mainly on sulfur dioxide, with the region near the sulfur atom as the electrophilic site that interacts with n-electron and π-electron pairs for a range of simple Lewis base molecules For tetrel bonds, the examples discussed involve the carbon atom of carbon dioxide as the electrophilic centre, while for pnictogen bonds the central nitrogen of the closely related molecule nitrous oxide is chosen Geometrical similarities within each series allow simple definitions of each type of non-covalent bond that are conformal with that recently advanced for the halogen bond, a related non-covalent interaction
TL;DR: Endohedral metallofullerenes Y2@C80 and Dy2@ C80 are obtained in the form of air-stable benzyl monoadducts, both of which feature an unpaired electron trapped between metal ions, thus forming a single-electron metal-metal bond.
Abstract: Increasing the temperature at which molecules behave as single-molecule magnets is a serious challenge in molecular magnetism. One of the ways to address this problem is to create the molecules with strongly coupled lanthanide ions. In this work, endohedral metallofullerenes Y2@C80 and Dy2@C80 are obtained in the form of air-stable benzyl monoadducts. Both feature an unpaired electron trapped between metal ions, thus forming a single-electron metal-metal bond. Giant exchange interactions between lanthanide ions and the unpaired electron result in single-molecule magnetism of Dy2@C80(CH2Ph) with a record-high 100 s blocking temperature of 18 K. All magnetic moments in Dy2@C80(CH2Ph) are parallel and couple ferromagnetically to form a single spin unit of 21 μB with a dysprosium-electron exchange constant of 32 cm−1. The barrier of the magnetization reversal of 613 K is assigned to the state in which the spin of one Dy centre is flipped. Single molecule magnets have demonstrated promise for information storage, molecular spintronics and quantum computing, but are limited by their low operational temperatures. Here, Popov and coworkers prepare a SMM with a high blocking temperature of 18 K by trapping two lanthanide ions with a single-electron bond inside a fullerene.
TL;DR: The confinement of platinum nanoparticles within the molybdenum disulfide layered structure leads to enhanced hydrogen evolution reaction activity and stability compared to catalysts dispersed on carbon support, which points a way forward for using bulk intercalated compounds for energy related applications.
Abstract: Interface confined reactions, which can modulate the bonding of reactants with catalytic centres and influence the rate of the mass transport from bulk solution, have emerged as a viable strategy for achieving highly stable and selective catalysis. Here we demonstrate that 1T′-enriched lithiated molybdenum disulfide is a highly powerful reducing agent, which can be exploited for the in-situ reduction of metal ions within the inner planes of lithiated molybdenum disulfide to form a zero valent metal-intercalated molybdenum disulfide. The confinement of platinum nanoparticles within the molybdenum disulfide layered structure leads to enhanced hydrogen evolution reaction activity and stability compared to catalysts dispersed on carbon support. In particular, the inner platinum surface is accessible to charged species like proton and metal ions, while blocking poisoning by larger sized pollutants or neutral molecules. This points a way forward for using bulk intercalated compounds for energy related applications. Interface confined reactions are a viable strategy for achieving stable and selective catalysts. Here, the authors demonstrate that 1T'-enriched lithiated MoS2 can reduce metal ions in situ, forming zero valent platinum nanoparticle-intercalated MoS2, with enhanced hydrogen evolution activity.
TL;DR: The absence of intercalating water molecules that cause the electrostatic screening (shielding) of hydrogen bonds in bulk water as the critical element for the enhanced hydrogen bonding around a hydrophobic solute is shown.
Abstract: Hydrophobicity plays an important role in numerous physicochemical processes from the process of dissolution in water to protein folding, but its origin at the fundamental level is still unclear. The classical view of hydrophobic hydration is that, in the presence of a hydrophobic solute, water forms transient microscopic “icebergs” arising from strengthened water hydrogen bonding, but there is no experimental evidence for enhanced hydrogen bonding and/or icebergs in such solutions. Here, we have used the redshifts and line shapes of the isotopically decoupled IR oxygen–deuterium (O-D) stretching mode of HDO water near small purely hydrophobic solutes (methane, ethane, krypton, and xenon) to study hydrophobicity at the most fundamental level. We present unequivocal and model-free experimental proof for the presence of strengthened water hydrogen bonds near four hydrophobic solutes, matching those in ice and clathrates. The water molecules involved in the enhanced hydrogen bonds display extensive structural ordering resembling that in clathrates. The number of ice-like hydrogen bonds is 10–15 per methane molecule. Ab initio molecular dynamics simulations have confirmed that water molecules in the vicinity of methane form stronger, more numerous, and more tetrahedrally oriented hydrogen bonds than those in bulk water and that their mobility is restricted. We show the absence of intercalating water molecules that cause the electrostatic screening (shielding) of hydrogen bonds in bulk water as the critical element for the enhanced hydrogen bonding around a hydrophobic solute. Our results confirm the classical view of hydrophobic hydration.
TL;DR: Segmented contracted Gaussian basis sets optimized at the one-electron exact two-component (X2C) level - including a finite size model for the nucleus - are presented for elements up to Rn.
Abstract: Segmented contracted Gaussian basis sets optimized at the one-electron exact two-component (X2C) level – including a finite size model for the nucleus – are presented for elements up to Rn. These basis sets are counterparts for relativistic all-electron calculations to the Karlsruhe “def2” basis sets for nonrelativistic (H–Kr) or effective core potential based (Rb–Rn) treatments. For maximum consistency, the bases presented here were obtained from the latter by modification and reoptimization. Additionally we present extensions for self-consistent two-component calculations, required for the splitting of inner shells by spin–orbit coupling, and auxiliary basis sets for fitting the Coulomb part of the Fock matrix. Emphasis was put both on the accuracy of energies of atomic orbitals and on the accuracy of molecular properties. A large set of more than 300 molecules representing (nearly) all elements in their common oxidation states was used to assess the quality of the bases all across the periodic table.
TL;DR: This biomolecule-derived binary carbon nitride polymer enables the generation of energized charge carrier with light-irradiation to induce photoredox reactions for stable hydrogen production and heterogeneous organosynthesis of C-O, C-C, C -N and N-N bonds.
Abstract: The construction of layered covalent carbon nitride polymers based on tri-s-triazine units has been achieved by using nucleobases (adenine, guanine, cytosine, thymine and uracil) and urea to establish a two-dimensional semiconducting structure that allows band-gap engineering applications. This biomolecule-derived binary carbon nitride polymer enables the generation of energized charge carrier with light-irradiation to induce photoredox reactions for stable hydrogen production and heterogeneous organosynthesis of C-O, C-C, C-N and N-N bonds, which may enrich discussion on chemical reactions in prebiotic conditions by taking account of the photoredox function of conjugated carbonitride semiconductors that have long been considered to be stable HCN-derived organic macromolecules in space.
TL;DR: A mild, efficient synthesis of sulfonyl fluorides from aryl and heteroaryl bromides utilizing palladium catalysis is described.
Abstract: A mild, efficient synthesis of sulfonyl fluorides from aryl and heteroaryl bromides utilizing palladium catalysis is described. The process involves the initial palladium-catalyzed sulfonylation of aryl bromides using DABSO as an SO2 source, followed by in situ treatment of the resultant sulfinate with the electrophilic fluorine source NFSI. This sequence represents the first general method for the sulfonylation of aryl bromides, and offers a practical, one-pot alternative to previously described syntheses of sulfonyl fluorides, allowing rapid access to these biologically important molecules. Excellent functional group tolerance is demonstrated, with the transformation successfully achieved on a number of active pharmaceutical ingredients, and their precursors. The preparation of peptide-derived sulfonyl fluorides is also demonstrated.
TL;DR: In this paper, the authors synthesized and characterized the (E)-1-(5-bromo-2-hydroxybenzylidene)semicarbazide (15BHS) by FT-IR, FT-Raman, UV, 1HNMR and 13CNMR spectral analysis.
TL;DR: A new Co(II)-based MOF, {[Co2(tzpa)(OH)(H2O)2]·DMF}n (1), was constructed by employing a tetrazolyl-carboxyl ligand H3tzpa, which possesses high CO2 adsorption capacity and significantly selective capture for CO2 over CH4 and CO in the temperature range of 298-333 K.
Abstract: A new Co(II)-based MOF, {[Co2(tzpa)(OH)(H2O)2]·DMF}n (1) (H3tzpa = 5-(4-(tetrazol-5-yl)phenyl)isophthalic acid), was constructed by employing a tetrazolyl-carboxyl ligand H3tzpa 1 possesses 1D tubular channels that are decorated by μ3–OH groups, uncoordinated carboxylate O atoms, and open metal centers generated by the removal of coordinated water molecules, leading to high CO2 adsorption capacity and significantly selective capture for CO2 over CH4 and CO in the temperature range of 298–333 K Moreover, 1 shows the chemical stability in acidic and basic aqueous solutions Grand canonical Monte Carlo simulations identified multiple CO2-philic sites in 1 In addition, the activated 1 as the heterogeneous Lewis and Bronsted acid bifunctional catalyst facilitates the chemical fixation of CO2 coupling with epoxides into cyclic carbonates under ambient conditions
TL;DR: The application of small molecules as catalysts for the diversification of natural product scaffolds is reviewed in this article, where principles that relate to the selectivity challenges intrinsic to complex molecular scaffolds are summarized.
Abstract: The application of small molecules as catalysts for the diversification of natural product scaffolds is reviewed. Specifically, principles that relate to the selectivity challenges intrinsic to complex molecular scaffolds are summarized. The synthesis of analogues of natural products by this approach is then described as a quintessential “late-stage functionalization” exercise wherein natural products serve as the lead scaffolds. Given the historical application of enzymatic catalysts to the site-selective alteration of complex molecules, the focus of this Review is on the recent studies of nonenzymatic catalysts. Reactions involving hydroxyl group derivatization with a variety of electrophilic reagents are discussed. C–H bond functionalizations that lead to oxidations, aminations, and halogenations are also presented. Several examples of site-selective olefin functionalizations and C–C bond formations are also included. Numerous classes of natural products have been subjected to these studies of site-sel...