Search

Comprehensive Summary: To understand the effects of chalcogen atoms on the crystal structure of the series of 3,7‐bis(methylchalcogeno)benzo[1,2‐b:4,5‐b′]dichalcogenophene‐based organic semiconductors, three benzodifuran derivatives (1—3) and dimethoxy derivatives of benzodithiophene and benzodiselenophene (4 and 7) were newly synthesized to complete the "3 × 3 matrix" of the oxygen‐, sulfur‐, and selenium‐derivatives (1—9). The crystal structures of 1—9 were classified into four classes, sandwich pitched π‐stack (1), dimeric (2 and 3), pitched π‐stack (4, 5, 7, 8, 9), and brickwork structure (6 and 9). The causes for the different crystal structures depending on the chalcogen atoms were investigated by the theoretical calculations, indicating that the chalcogen atoms in the core and substituents primarily affected the packing structures. Although the crystal growth in the vapor phase afforded different polymorphs, the relationship between the crystal structure and the carrier transport property was carefully investigated. With these comprehensive evaluations, we conclude that; i) methylchalcogenolation is a powerful tool to alter the packing structure, ii) each methylchalcogeno group has its features that largely influence the intermolecular interaction and electronic structure in the solid state, and iii) organic semiconductors being crystallizable into appropriate pitched π‐stack structures are promising as high‐performance active materials for FET applications. [ABSTRACT FROM AUTHOR]

Integration of electronic and strain effects with tailored structures is significant to tuning the electrocatalytic activity and stability of the electrocatalysts for the oxygen reduction reaction (ORR). In this study, one‐dimensional PtFe hollow nanochains are synthesized by a facile and effective method, which exhibit a highly open and porous structure. The modulated electronic and strain effects of Pt atoms are verified by extensive structural characterizations, and the mass and specific activities of the prepared catalyst are roughly 7.45 and 12.44 times higher than those of the commercial Pt/C catalyst, respectively. Remarkably, the catalyst demonstrates robust performance with negligible activity decay after an accelerated durability test for 30,000 cycles. The high activity of the catalyst is probably due to the optimized absorption affinity of Pt‐O accelerating the reaction kinetics induced by the cooperation of Fe atoms as well as the unique hollow and curved structures. This study provides new insights into the rational design of high‐performance ORR catalysts with considerable durability. [ABSTRACT FROM AUTHOR]

Fabricating single‐atom electrodes via atomic dispersion of active metal atoms into monolithic metal supports is of great significance to advancing the lab‐to‐fab translation of the electrochemical technologies. Here, we report an inherent oxide anchoring strategy to fasten ligand‐free isolated Ru atoms on the amorphous layer of monolithic Ti support by regulating the electronic metal‐support interactions. The prepared Ru single atom electrode exhibited exceptional electrochemical chlorine evolution activity, three orders of magnitude higher mass activity than that of commercial dimensionally stable anode, and also selectively reduced nitrate to ammonia with an unprecedented ammonia yield rate of 22.2 mol g−1 h−1 at −0.3 V. Furthermore, the Ru single atom monolithic electrode can be scaled up from 2×2 cm to 25×15 cm at least, thus demonstrating great potential for industrial electrocatalytic applications. [ABSTRACT FROM AUTHOR]

The electronic energy and the polarizability of a confined hydrogen molecular ion in the ground state and the first excited state, for cavities of different volumes, are calculated using the variational method. In the treatment adopted an alternative molecular wave function is introduced with only one variational parameter and based on wave functions used for confined atoms. © 2016 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Nitrogen-containing polycyclic aromatic hydrocarbons are very attractive compounds for organic electronics applications. Their low-lying LUMO energies points towards a potential use as n-type semiconductors. Furthermore, they are expected to be more stable under ambient conditions, which is very important for the formation of semiconducting films, where materials with high purity are needed. In this study, the syntheses of naphtho[2,3- g]quinoxalines and pyrazino[2,3- b]phenazines is presented by using reaction conditions, that provide the desired products in high yields, high purity and without time-consuming purification steps. The HOMO and LUMO energies of the compounds are investigated by cyclic voltammetry and UV/Vis spectroscopy and their dependency on the nitrogen content and the terminal substituents are examined. The photostability and the degradation pathways of the naphtho[2,3- g]quinoxalines and pyrazino[2,3- b]phenazines are explored by NMR spectroscopy of irradiated samples affirming the large influence of the nitrogen atoms in the acene core on the degradation process during the irradiation. Finally, by identifying the degradations products of 2,3-dimethylnaphtho[2,3- g]quinoxaline it is possible to track down the most reactive position in the compound and, by blocking this position with nitrogen, to strongly increase the photostability. [ABSTRACT FROM AUTHOR]

The most intriguing feature of metal-metal bonds in inorganic compounds is an apparent lack of correlation between the bond order and the bond length. In this study, we combine a variety of literature data obtained by quantum chemistry and our results based on the empirical bond valence model (BVM), to confirm for the first time the existence of a normal exponential correlation between the effective bond order (EBO) and the length of the metal-metal bonds. The difference between the EBO and the formal bond order is attributed to steric conflict between the (TM) n cluster (TM=transition metal) and its environment. This conflict, affected mainly by structural type, should cause high lattice strains, but electron redistribution around TM atoms, evident from the BVM calculations, results in a full or partial strain relaxation. [ABSTRACT FROM AUTHOR]

Single-crystal X-ray diffraction of Cs3ScSi6O15 shows the presence of main reflections and satellite reflections up to the fourth order along the c* direction. The (3+1)-dimensional incommensurately modulated structure was solved in superspace group [ a = 13.861 (1), c = 6.992 (1) Å, V = 1163.4 (2) Å3] with a modulation wavevector q = 0.14153 (2) c*. Refinement of three modulation waves for positional and anisotropic displacement parameter values for all atoms converged to Robs values for all, main and satellite reflections of first, second and third order of 0.0200, 0.0166, 0.0181, 0.0214 and 0.0303, respectively. Cs3ScSi6O15 forms a mixed tetrahedral-octahedral framework with prominent six-membered rings of [SiO4]-tetrahedra interconnected by [ScO6]-octahedra. Apart from Sc, all atoms are strongly affected by positional modulation with maximum atomic displacements of up to 0.93 Å causing rigid polyhedral arrangements to perform tilt and twist movements relative to each other, such as a rotation of the Sc-octahedra around the -axis by over 38°. Cs has an irregular coordination environment; however, considering distances up to 3.5 Å, the bond-valence sum changes by no more than 0.02 as a function of t and thus overall kept at a level of ca 1.075. [ABSTRACT FROM AUTHOR]

A sterically strained 32π‐electron antiaromatic bis‐BODIPY macrocycle in which two BODIPY fragments are linked by p‐divinylbenzene groups was prepared and characterized. Unlike regular BODIPYs, the fluorescence in this macrocycle is quenched. The broad signals in the NMR spectra of the macrocycle were explained by the vibronic freedom of the p‐divinylbenzene fragments. The possible diradicaloid nature of the macrocycle was excluded on the basis of variable‐temperature EPR spectra in solution and in solid state, which is indicative of its closed‐shell quinoidal structure. The meso‐C−H bond in the macrocycle and its precursor BODIPY dialdehyde 3 forms a weak hydrogen bond with THF and is susceptible for the nucleophilic attack by organic amines and cyanide anion. The reaction products of such a nucleophilic attack have meso‐sp3 carbon atoms and were characterized by NMR, mass spectrometry and, in one case, X‐ray crystallography. Unlike the initial bis‐BODIPY macrocycle, the adducts have strong fluorescence in the 400 nm region. The electronic structure and spectroscopic properties of new chromophores were probed by density functional theory (DFT) and time‐dependent DFT (TDDFT) calculations and correlate well with the experimental data. [ABSTRACT FROM AUTHOR]

A new copper/I2‐catalyzed hydroxyamination of alkenes of unsaturated keto oximes with DMSO as the hydroxy oxygen atom source and medium for assembling 2‐(2‐hydroxyalkyl)‐3,4‐dihydro‐2H‐pyrrole 1‐oxides is described. Mechanistic studies suggest that the reaction is terminated by a single electron oxidation and subsequent nucleophilic reaction. [ABSTRACT FROM AUTHOR]

Graphene edges exhibit a highly localized density of states that result in increased reactivity compared to its basal plane. However, exploiting this increased reactivity to anchor and tune the electronic states of single atom catalysts (SACs) remains elusive. To investigate this, a method to anchor Pt SACs with ultra‐low mass loadings at the edges of edge‐rich vertically aligned graphene (as low as 0.71 µg Pt cm–2) is developed. Angle‐dependent X‐ray absorption spectroscopy and density‐functional theory calculations reveal that edge‐anchored Pt SACs has a robust coupling with the π‐electrons of graphene. This interaction results in a higher occupancy of the Pt 5d orbital, shifting the d‐band center toward the Fermi level, improving the adsorption of *H for the hydrogen evolution reaction (HER). Pt primarily coordinated to the graphene edge shows improved alkaline HER performance compared to Pt coordinated in mixed environments (turnover frequencies of 22.6 and 10.9 s–1 at an overpotential of 150 mV, respectively). This work demonstrates an effective route to engineering the coordination environment of Pt SACs by using the graphene edge for enhanced energy conversion reactions. [ABSTRACT FROM AUTHOR]

A novel neutral diradical of π‐extended phenalenyl derivative having three oxo‐groups, tri‐tert‐butyl‐1,4,7‐trioxophenalenyl, and two types of the corresponding σ‐dimers were investigated. Quantum chemical calculations showed that the neutral diradical is in triplet ground state having doubly degenerate singly occupied molecular orbitals. The neutral diradical undergoes a σ‐dimerization, generating two types of σ‐dimers immediately after the preparation. One of the σ‐dimers, which was selectively generated in the crystalline state, was a close‐shell dimer linked through double‐σ‐bonds on the phenalenyl skeleton with a long C−C bond length of 1.66 Å. The other σ‐dimer, which existed only in the solution state, was a peroxy‐linked open‐shell dimer in which one σ‐bond was formed between two oxygen atoms. Furthermore, the temperature‐dependent 1H NMR and ESR spectra revealed that these σ‐dimers are in equilibrium in the solution state by the reversible σ‐bond formation/cleavage via the neutral diradical as a key intermediate. [ABSTRACT FROM AUTHOR]

The development of new approaches to installing diverse carbon fragments to a nitrogen atom has attracted considerable attention in chemical science. While numerous strategies have been devised to forge C(sp3)−N bonds, one conceptually powerful and straightforward approach is to insert a transformable sp3‐carbon unit onto a nitrogen atom for modular diversification. Here we describe the successful synthesis of halo‐diborylmethanes and their applications to the preparation of nitrogen‐substituted diborylmethanes through their homologative coupling with a variety of nitrogen nucleophiles including biologically relevant molecules. This process exhibits a remarkably broad substrate scope, and the usefulness of the obtained compounds is demonstrated by the modular diversification of the diborylmethyl group to access various nitrogen‐containing molecules. [ABSTRACT FROM AUTHOR]

Herein, we report a method that provides an array of benzocyclobutanol and benzocyclobutylamine derivatives with broad substrate scope and good functional group tolerance under mild reaction conditions. The reaction proceeds by engaging triplet biradical atom transfer of olefinic compounds in the activation of remote C(sp3)−H bonds upon visible‐light irradiation. The reaction mechanism involves the generation of triplet excited state of diarylethylene derivative and subsequent HAT process, and then the further ring‐closing reaction affording the product via an electrocyclization process. The plausible mechanism is supported by control and deuterium labeling experiments, kinetic analysis, and DFT calculations. [ABSTRACT FROM AUTHOR]

Here, we studied two different 2D monolayer systems (i.e., h‐BN and SiC), which exhibit unique electronic and magnetic properties. We analyzed the effects of Transition Methods (TM) doped atoms (i.e., Mn, Ni, and Sc) on the single vacancy (SV) h‐BN and SiC systems using first principles calculations. Through comparison we found that Mn substitution in SV h‐BN and SiC can modify their electronic and magnetic properties having larger magnetic moment as compared to other dopants (i.e., Ni and Sc.). Band structure and PDOS plots confirmed that TM doping in SV h‐BN can convert the pure h‐BN (insulator) to semiconductor, metal, or semi‐metal, it is also observed from the results that Mn‐doped h‐BN has higher band gap approximately equal to Eg ~ 2.7 eV during the negative spin and has smaller band gap, that is, (Eg ~ 1.1 eV) during the positive spin. Similarly doping with the TM atoms on the SV SiC monolayer system can convert pure SiC to metal or half metal. In addition, Mn‐doped SiC showed semimetal property having 0 eV band gap. These finding will help us to vary the electronic and magnetic properties of the pure h‐BN and SiC sheets which can be used for the opto‐electronic and spintronic applications. [ABSTRACT FROM AUTHOR]

Closing both the carbon and nitrogen loops is a critical venture to support the establishment of the circular, net‐zero carbon economy. Although single atom catalysts (SACs) have gained interest for the electrochemical reduction reactions of both carbon dioxide (CO2RR) and nitrate (NO3RR), the structure–activity relationship for Cu SAC coordination for these reactions remains unclear and should be explored such that a fundamental understanding is developed. To this end, the role of the Cu coordination structure is investigated in dictating the activity and selectivity for the CO2RR and NO3RR. In agreement with the density functional theory calculations, it is revealed that Cu‐N4 sites exhibit higher intrinsic activity toward the CO2RR, whilst both Cu‐N4 and Cu‐N4−x‐Cx sites are active toward the NO3RR. Leveraging these findings, CO2RR and NO3RR are coupled for the formation of urea on Cu SACs, revealing the importance of *COOH binding as a critical parameter determining the catalytic activity for urea production. To the best of the authors' knowledge, this is the first report employing SACs for electrochemical urea synthesis from CO2RR and NO3RR, which achieves a Faradaic efficiency of 28% for urea production with a current density of −27 mA cm–2 at −0.9 V versus the reversible hydrogen electrode. [ABSTRACT FROM AUTHOR]

The development of a mild and general method for C(sp3)−H functionalization of cyclic amines has been an ongoing challenge. In this work, we describe the copper‐catalyzed enantioselective C(sp3)−H alkynylation of unactivated cyclic 2‐iodo‐benzamide under photo‐irradiation by intramolecular 1,5‐hydrogen atom transfer (HAT). The employment of a new bisoxazoline diphenylamine ligand, in conjunction with 1,1′‐bi‐2‐naphthol, which significantly improved the reduction potential of the copper complex, was the key to success of this chemistry. Mechanistic and computational studies supported that the new copper complex served the dual role as a photoredox and coupling catalyst, the reaction went through a radical process, and the intramolecular 1,5‐HAT process was involved in the rate‐limiting step. Apart from the broad substrate scope including unprecedented benzocyclic amines, this method also showed excellent diastereoselectivity in 2‐monosubstituted cyclic amines via substrate control. [ABSTRACT FROM AUTHOR]

A novel Ag doped Au44(C10H9)28 nanocluster (C10H10=1‐ethynyl‐2,4‐dimethylbenzene) was synthesized, that is, Ag4+xAu40‐x(C10H9)28 (x≤6), where four Ag positions located in the surface staple of the cluster have been determined, while six Au/Ag co‐occupying positions have been found in the metal core of the cluster. The electronic configuration of Au44(C10H9)28 cluster is significantly disturbed by doping Ag atoms, hence promoting the electron transport capability. For the two‐electron conversion reaction of CO2 to CO in electrochemical reduction of CO2, Ag doped Ag4+xAu40‐x(C10H9)28 catalyst exhibited higher effective activity and long‐term stability than its counterpart Au44(C10H9)28 catalyst. [ABSTRACT FROM AUTHOR]

The silanide [Si4{N(SiMe3)Dipp}3]− (1) transforms into the anionic siliconoid cluster [Si7{N(SiMe3)Dipp}3]− (2) with four unsubstituted silicon atoms as a contact ion pair with [K([18]crown‐6)] in C6D6 at room temperature within five weeks. Anion 2 was investigated by natural population analysis and visualization of intrinsic atomic orbitals. Magnetically induced current‐density calculations of 2 revealed two distinct strong diatropic vortices that sum up in one direction and create a strongly shielded apical silicon atom in 2. [ABSTRACT FROM AUTHOR]

Accurate prediction of binding poses is crucial to structure‐based drug design. We employ two powerful artificial intelligence (AI) approaches, data‐mining and machine‐learning, to design artificial neural network (ANN) based pose‐scoring function. It is a simple machine‐learning‐based statistical function that employs frequent geometric and chemical patterns of interacting atoms at protein‐ligand interfaces. The patterns are derived by mining interfaces of "native" protein‐ligand complexes. Each interface is represented by a graph where nodes are atoms and edges connect protein‐ligand interfacial atoms located within certain cutoff distance of each other. Applying frequent subgraph mining to these interfaces provides "native" frequent patterns of interacting atoms. Subsequently, given a pose for a protein‐ligand complex of interest, the pose‐scoring function (the information‐processing unit or neuron) calculates the degree of matching between the interaction patterns present at the pose's interface and the native frequent patterns. The pose‐scoring function takes into account the frequency of occurrence of the matching native patterns, the size of the match, and the degree of geometrical similarity between pose‐specific and matching native frequent patterns. This novel "multi‐body interaction" pose‐scoring function (MBI‐Score) was validated using two databases, PDBbind and Astex‐85, and it outperformed seven commonly used commercial scoring functions. MBI‐Score is available at www.khashanlab.org/mbi‐score. [ABSTRACT FROM AUTHOR]

The modification of Pd cocatalysts is considered to be an effective strategy to improve H2O2 production of photocatalysts because it can accelerate the reaction rate of O2 reduction. However, the strong adsorption between O2 molecules and Pd atoms is not conducive to the formation of intermediate HOO* and leads to the further reduction of H2O2 to H2O, thus limiting the improvement of H2O2 production. To solve the issue, in this work, Cu–Pd alloy cocatalysts are selectively modified on the electron‐rich facets of BiVO4 via facile photoinduced deposition and subsequent galvanic displacement. DFT calculations indicate that the incorporation of Cu atoms to Pd atoms weakens the oxygen adsorption energy and HOO* binding energy on Pd atom surfaces, thus increasing the activity and selectivity of O2 reduction to H2O2. Further experimental results show that the optimized Cu‐Pd/BiVO4(5:1) photocatalyst exhibits markedly boosted activity for H2O2 production (2189 µmol L‐1), which is 3.2‐fold higher than that of BiVO4 with modification of 0.3 wt% Pd cocatalyst (675 µmol L‐1). Additionally, the incorporation of metal Cu enables the economic utilization of Pd atoms and reduces the expense of the Pd cocatalyst. [ABSTRACT FROM AUTHOR]

It is an obstacle to precisely manipulate a doped heteroatom into a desired position in a metal nanocluster. Herein, we overcome this difficulty to obtain Pt1Au37(SCH2PhtBu)24 and Pt2Au36(SCH2PhtBu)24 nanoclusters via controllably doping Pt atoms into the kernels of Au38(SCH2PhtBu)24. We reveal that asymmetrical doping of one Pt atom into either of the cores of Au38(SCH2PhtBu)24 elevates the relative energy of the HOMO (highest occupied molecular orbital) accompanied by one valence electron loss of Pt1Au37(SCH2PhtBu)24, compared to Au38(SCH2PhtBu)24 with 14 electrons, while symmetrical doping of two Pt atoms into the cores of Au38(SCH2PhtBu)24 narrows the HOMO–LUMO gap (LUMO: lowest unoccupied molecular orbital) of Pt2Au36(SCH2PhtBu)24 with two valence electrons less. Consequently, Pt1Au37(SCH2PhtBu)24 shows an electron‐spin‐induced high activity for CO2 electroreduction, whereas Pt2Au36(SCH2PhtBu)24 is least efficient and Au38(SCH2PhtBu)24 has a decent performance. [ABSTRACT FROM AUTHOR]

Many chemicals known today are partially or fully aromatic, since a ring framework experiences additional stabilization through the delocalization of π‐electrons. While aromatic rings with equal numbers of π‐electrons and ring atoms such as benzene are particularly stable, those with the minimally required two π‐electrons are very rare and yet remain limited to three‐ and four‐membered rings if not stabilized in the coordination sphere of heavy metals. Here we report the facile synthesis of a dipotassium cyclopentagallene, a unique example of a five‐membered aromatic ring stabilized by only two π‐electrons. Single‐crystal X‐ray diffraction revealed a planar Ga5 ring with almost equal gallium–gallium bond lengths, which together with computational and spectroscopic data confirm its aromatic character. Our results prove that aromatic stabilization goes far beyond what has previously been assumed as minimum π‐electron count in a five‐atom ring fragment. [ABSTRACT FROM AUTHOR]

The growth of (semi‐)metal clusters is pivotal for nucleation processes in gaseous and condensed phases. We now report the isolation of intermediates during the expansion of a stable unsaturated silicon cluster (siliconoid) by a single germanium atom through a sequence of substitution, rearrangement and reduction. The reaction of ligato‐lithiated hexasilabenzpolarene LiSi6Tip5 (1Li⋅(thf)2, Tip=2,4,6‐triisopropylphenyl) with GeCl2⋅NHC (NHC=1,3‐diisopropyl‐4,5‐dimethylimidazol‐2‐ylidene) initially yields the product with exohedral germanium(II) functionality, which then inserts into an Si−Si bond of the Si6 scaffold. The concomitant transfer of the chloro functionality from germanium to an adjacent silicon preserves the electron‐precise nature of the formed endohedral germylene. Full incorporation of the germanium heteroatom to the Si6Ge cluster core is finally achieved either by reduction under loss of the coordinating NHC or directly by reaction of 1Li⋅(thf)2 with GeCl2⋅1,4‐dioxane. [ABSTRACT FROM AUTHOR]

The reactivity of ferrocene‐based N‐heterocyclic tetrylenes [{Fe(η5−C5H4−NSitBuMe2)2}E] (E=Ge, Sn, Pb) towards mesityl azide (MesN3) is compared with that of PPh2‐functionalised congeners exhibiting two possible reaction sites, namely the EII and PIII atom. For E=Ge and Sn the reaction occurs at the EII atom, leading to the formation of N2 and an EIV=NMes unit. The germanimines are sufficiently stable for isolation. The stannanimines furnish follow‐up products, either by [2+3] cycloaddition with MesN3 or, in the PPh2‐substituted case, by NMes transfer from the SnIV to the PIII atom. Whereas [{Fe(η5−C5H4−NSitBuMe2)2}Pb] and other diaminoplumbylenes studied are inert even under forcing conditions, the PPh2‐substituted congener forms an addition product with MesN3, thus showing a behaviour similar to that of frustrated Lewis pairs. The germylenes of this study afford copper(I) complexes with CuCl, including the first structurally characterised linear dicoordinate halogenido complex [CuX(L)] with a heavier tetrylene ligand L. [ABSTRACT FROM AUTHOR]

We developed time‐atom economic regio‐ and chemoselective sulfonyl radical triggered 5‐exo‐dig cyclization of unactivated 1,6‐enynes with sulfonyl halides under metal, additive‐free reaction conditions to achieve highly substituted five‐membered heterocyclic compounds. This transformation creates three new bonds, such as C−SO2, C−C, and active C−I/Br bonds. Importantly, one‐pot protocols produce desired products directly from sodium sulfinates and have an additional advantage such as minimising chemical waste, saving time, and simplifying practical aspects compared to existing protocols. [ABSTRACT FROM AUTHOR]

Realizing the synergy between active site regulation and rational structural engineering is essential in the electrocatalysis community but still challenging. Here, a matrix‐confined co‐pyrolysis strategy based on molecular bridging is demonstrated to realize highly dispersed Fe atoms on stereoassembled carbon framework. Both polyacrylonitrile matrix and organic linker from metal–organic frameworks (MOFs) provide sufficient N‐anchoring sites for the generation of Fe−N4 moieties. A high Fe loading of 2.9 wt.% is readily achieved based on the scalable approach without post‐treatment. Owing to the presence of highly exposed Fe−N−C sites and well‐tuned pore structures, isolated Fe atoms on porous carbon nanofiber framework (Fe−SA/NCF) exhibits decent oxygen reduction activity and stability in alkaline conditions via a near four‐electron path, demonstrating superior performance as air cathode for zinc‐air batteries (ZABs) to commercial Pt/C catalyst. [ABSTRACT FROM AUTHOR]

Reversible‐deactivation radical polymerizations (RDRPs) have revolutionized synthetic polymer chemistry. Nowadays, RDRPs facilitate design and preparation of materials with controlled architecture, composition, and functionality. Atom transfer radical polymerization (ATRP) has evolved beyond traditional polymer field, enabling synthesis of organic–inorganic hybrids, bioconjugates, advanced polymers for electronics, energy, and environmentally relevant polymeric materials for broad applications in various fields. This review focuses on the relation between ATRP technology and the 12 principles of green chemistry, which are paramount guidelines in sustainable research and implementation. The green features of ATRP are presented, discussing the environmental and/or health issues and the challenges that remain to be overcome. Key discoveries and recent developments in green ATRP are highlighted, while providing a perspective for future opportunities in this area. [ABSTRACT FROM AUTHOR]

Single‐atom catalysts (SACs) with a maximum atom utilization efficiency have received growing attention in heterogeneous catalysis. The supporting substrate that provides atomic‐dispersed anchoring sites and the local electronic environment in these catalysts is crucial to their activity and stability. Here, inspired by N‐doped graphene substrate, the role of N is explored in transition metal nitrides for anchoring single metal atoms toward single‐atom catalysis. A pore‐rich metallic vanadium nitride (VN) nanosheet is fabricated as one supporting‐substrate example, whose surface features abundant unsaturated N sites with lower binding energy than that of widely used N‐doped graphene. Impressively, it is found that this support can anchor nearly all platinum‐group single atoms (e.g., platinum, palladium, iridium, and ruthenium), and even be extendable to multiple SACs, i.e., binary (Pt/Pd) and ternary (Pt/Pd/Ir). As a proof‐of‐concept application for hydrogen production, Pt‐based SAC (Pt1‐VN) performs excellently, exhibiting a mass activity up to 22.55 A mg−1Pt at 0.05 V and a high turnover frequency value close to 0.350 H2 s−1, superior to commercial platinum/carbon catalyst. The catalyst's durability can be further improved by using binary (Pt1Pd1‐VN) SAC. This work provides inexpensive and durable nitride‐based support, giving a possible pathway for universally constructing platinum‐group SACs. [ABSTRACT FROM AUTHOR]

Atomic systems with exponential-cosine-screened Coulomb (ECSC) or static screened Coulomb (SSC) potentials have drawn considerable attention recently due to the possible applications to atoms in plasma environments. In this work, we develop a computing scheme to deal with the electron-electron correlation terms with the screened Coulomb interactions instead of the conventional expansion method using the Gegenbauer's addition theorem. Based on this approach, we investigate the helium atom with the ECSC potentials. Bypassing the complex expansion functions for electron-electron interactions, the proposed approach simplifies the calculations greatly and provides an advantage on programming. The results are found to be in good agreement with the existing data. Bound-state energies, oscillator strengths, and multipole polarizabilities varying with the screening parameters are presented. Comparisons of the ECSC potentials are made with the SSC potentials. The influence of screening effect on the energies, oscillator strengths, and polarizabilities is discussed. © 2015 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Quantum effects in hybrid atomic optomechanics in a system comprising a cloud of atoms and a mobile mirror mediated by a single-mode cavity are studied. Tripartite nonlocality is observed in the atom-light-mirror system, as demonstrated by the violation of the Mermin-Klyshko (MK) inequality. It has been shown [C. Genes, et al., PRA 77, 050307 (R) (2008)] that tripartite entanglement is optimized when the cavity is resonant with the anti-Stokes sideband of the driving laser and the atomic frequency matches the Stokes one. However, we show that this is not the case for the nonlocality. The MK function achieves minima when the atoms are resonant with both the Stokes and anti-Stokes sidebands, and unexpectedly, we find violation of the MK inequality only in a parameter region where entanglement is far from being maximum. A negative relation exists between nonlocality and entanglement with consideration of the possibility of bipartite nonlocality in the violation of the MK inequality. We also study the non-classicality of the mirror by post-selected measurements, e.g. Geiger-like detection, on the cavity and/or the atoms. We show that with feasible parameters Geiger-like detection on the atoms can effectively induce mechanical non-classicality. [ABSTRACT FROM AUTHOR]

An unusual phase transition P4/ mnc→ has been detected after cooling the (NH4)3TiF7 compound. Some TiF6 octahedra, which are disordered in the room-temperature tetragonal structure, become ordered in the low-temperature cubic phase due to the disappearance of the fourfold axis. Other TiF6 octahedra undergo large rotations resulting in huge displacements of the F atoms by 1.5-1.8 Å that implies a reconstructive phase transition. It was supposed that phases P4/ mbm and could be a high-temperature phase and a parent phase, respectively, in (NH4)3TiF7. Therefore, the sequence of phase transitions can be written as → P4/ mbm→ P4/ mnc→. The interrelation between (NH4)3TiF7, (NH4)3GeF7 and (NH4)3PbF7 is found, which allows us to suppose phase transitions in relative compounds. [ABSTRACT FROM AUTHOR]

This work extends previous efforts to model diffuse scattering from PZN (PbZn1/3Nb2/3O3). Earlier work [Welberry et al. (2005). J. Appl. Cryst. 38, 639-647; Welberry et al. (2006). Phys. Rev. B, 74, 224108] is highly prescriptive, using Monte Carlo simulation with very artificial potentials to induce short-range-order structures which were deduced as necessary from inspection of the data. While this gives valid results for the nature of the local structure, it does not strongly relate these structures to underlying crystal chemistry. In that work, the idea of the bond-valence sum was used as a guide to the expected behaviour of the atoms. This paper extends the use of the bond-valence sum from a qualitative guide to becoming a key aspect of the potential experienced by the atoms, through the idea of the global instability index, whose square has been shown to be proportional to the density functional theory energy of some systems when close to the minimum energy configuration. [ABSTRACT FROM AUTHOR]

Analysis of EXAFS data measured on a material with a disordered local configuration environment around the absorbing atom can be challenging owing to the proliferation of photoelectron scattering paths that must be considered in the analysis. In the case where the absorbing atom exists in multiple inequivalent sites, the problem is compounded by having to consider each site separately. A method is proposed for automating the calculation of theory for inequivalent sites, then averaging the contributions from sufficiently similar scattering paths. With this approach, the complexity of implementing a successful fitting model on a highly disordered sample is reduced. As an example, an analysis of Ti K-edge data on zirconolite, CaZrTi2O7, which has three inequivalent Ti sites, is presented. [ABSTRACT FROM AUTHOR]

An efficient procedure and computer program are outlined for fitting numerical X-ray and electron scattering factors with the correct inclusion of all physical constraints. The numerical electron scattering factors have been parameterized using five analytic non-relativistic hydrogen electron scattering factors as basis functions for 103 neutral atoms of the periodic table. The inclusion of the correct physical constraints in the electron scattering factor and its derived quantities allows the use of the new parameterization in different fields. In terms of quality of the fit, the proposed parameterization of the electron scattering factor is one order of magnitude better than the previous analytic fittings. [ABSTRACT FROM AUTHOR]

We present the analytical theory for the second derivative of the electronic energy with respect to the scaling factor of the compression cavity within the eXtreme pressure polarizable continuum model (XP‐PCM) for the study of compressed atomic and molecular systems. The theory has been exploited to study compression response functions describing how the atomic/molecular properties are effected by an external pressure. The response functions considered include the atomic compressibility and the pressure coefficients of the ionization energy (IE) and electron affinity (EA). The theory has been validated by numerical application to compressed neon, argon, and krypton atoms. [ABSTRACT FROM AUTHOR]

A solvent‐free method for the synthesis of quaternary ammonium salts (QAS) by iodoquaternization of alkenes with N‐heteroarenes was reported. Its advantages lie in energy‐saving and clean production by using iodine as the oxidant and manual grinding the starting materials, together with the complete atom economy and low process mass intensity (PMI) value. Demonstrated by 50 examples, the generated QAS was proved to be able to produce valuable chemicals, such as biological protease inhibitors, anti‐cancer agents, and organic fluorescent materials. [ABSTRACT FROM AUTHOR]

Herein, we report a polar‐radical relay strategy for α‐C−H amination of cyclic amines with N‐chloro‐N‐sodio‐carbamates. The relay is initiated by in situ generation of cyclic iminium intermediate using N‐iodosuccinimide (NIS) oxidant as an initiator, which then operates through a series of polar (addition and elimination) and radical (homolysis, hydrogen‐ and halogen atom transfer) reactions to enable the challenging C−N bond formation in a controlled manner. A broad range of α‐amino cyclic amines were readily accessed with excellent regioselectivity, and the superb applicability was further demonstrated by functionalization of biologically relevant compounds. [ABSTRACT FROM AUTHOR]

An approach is developed for the fast calculation of the interacting quantum atoms energy decomposition (IQA) from the information contained in the first order reduced density matrix only. The proposed methodology utilizes an approximate exchange‐correlation density from Density Matrix Functional Theory without the need to evaluate the correlation‐exchange contribution directly. Instead, weight factors are estimated to decompose the exact Vxc into atomic and pairwise contributions. In this way, the sum of the IQA contributions recovers the energy obtained from the electronic structure calculation. This method can, hence, be applied to obtain atomic contributions in excited states on the same footing as in their ground states using any method that delivers the reduced first‐order density matrix. In this way, one can locate chromophores from first principles quantum chemical calculations. Test calculations on the ground and excited states of a set of small molecules indicate that the scaled atomic contributions reproduce vertical electronic transition energies calculated exactly. This approach may be useful to extend the applicability of the IQA approach in the study of large photochemical systems especially when the calculations of the second order reduced density matrices is prohibitive or not possible. [ABSTRACT FROM AUTHOR]

The fundamental relationship between structure and properties, which is called "structure‐property", plays a vital role in the rational designing of high‐performance catalysts for diverse electrocatalytic applications. Low‐dimensional (LD) nanomaterials, including 0D, 1D, 2D materials, combined with low‐nuclearity metal atoms, ranging from single atoms to subnanometer clusters, are currently emerging as rising star nanoarchitectures for heterogeneous catalysis due to their well‐defined active sites and unbeatable metal utilization efficiencies. In this work, a comprehensive experimental and theoretical review is provided on the recent development of single atom and atomic cluster‐decorated LD platforms towards some typical clean energy reactions, such as water‐splitting, nitrogen fixation, and carbon dioxide reduction reactions. The upmost attractive structural properties, advanced characterization techniques, and theoretical principles of these low‐nuclearity electrocatalysts as well as their applications in key electrochemical energy devices are also elegantly discussed. [ABSTRACT FROM AUTHOR]

Organic compounds with tunable structures and high capacities are promising electrode materials for batteries. Cyclic organosulfide (i. e., lenthionine), as a natural material that can provide excellent ratio of effective atoms (S) and non‐efficient atoms (C, H, and others), has a high theoretical specific capacity of 853.6 mAh g−1. However, the multiphase transformation causes rapid capacity decay and hysteresis of charge/discharge voltage plateaus. To overcome these issues, a receptor, phenyl disulfide (PDS), was introduced to truncate subsequent transformations directly from the source and change the reaction path, inhibit the capacity decay, and improve the cycling stability. After 500 cycles, the capacity retention was 81.1 % with PDS, which was in sharp contrast to that (35.6 %) of the control cell. This study helps to understand the electrochemistry mechanism of biomass‐derived lenthionine used as a high‐capacity cathode material for rechargeable lithium batteries, also offering a strategy to overcome its inherent issues. [ABSTRACT FROM AUTHOR]

The use of single atoms (SAs) has become a highly investigated topic in heterogeneous catalysis, electrocatalysis, and most recently also in photocatalysis. In the field of photocatalysis, Pt SAs on TiO2 have been reported to be a highly efficient co‐catalyst in solar H2 production. Herein, the deposition of Pt SAs and nanoparticles on titania nanosheets is investigated. In particular, the Pt species responsible for the high co‐catalytic activity using a cyanide leaching process is elucidated. It is shown that neither Pt0 species nor the majority of Pt SAs do significantly contribute to the co‐catalytic activity of platinum on TiO2. In fact, >90% of the Pt of a standard deposition are non‐active and can be removed by cyanide leaching without activity loss—as a consequence, the remaining Pt SAs amount to a remarkable turnover frequency of 4.87 × 105 h−1 for H2 evolution. [ABSTRACT FROM AUTHOR]

An experimental scheme for the measurement of entanglement between two two‐level atoms is proposed. This scheme requires one of the two entangled atoms to interact with a cavity field dispersively, and it is shown that by measuring the zero time‐delay second‐order coherence function of the cavity field, one can measure the concurrence of an arbitrary Bell‐like atomic two‐qubit state. As this scheme requires only one of the atoms to interact with the measured cavity, the entanglement quantification becomes independent of the location of the other atom. Therefore, this scheme can have important implications for entanglement quantification in distributed quantum systems. [ABSTRACT FROM AUTHOR]

The new phase Be3Ru crystallizes with TiCu3‐type structure (space group Pmmn (59), a=3.7062(1) Å, b=4.5353(1) Å, c=4.4170(1) Å), a coloring variant of the hexagonal closest packing (hcp) of spheres. The electronic structure revealed that Be3Ru has a pseudo‐gap close to the Fermi level. A strong charge transfer from Be to Ru was observed from the analysis of electron density within the Quantum Theory of Atoms in Molecules (QTAIM) framework and polar three‐ and four‐atomic Be−Ru bonds were observed from the ELI−D (electron localizability indicator) analysis. This situation is very similar to the recently investigated Be5Pt and Be21Pt5 compounds. The unusual crystal chemical feature of Be3Ru is that different charged species belong to the same closest packing, contrary to typical inorganic compounds, where the cationic components are located in the voids of the closest packing formed by anions. Be3Ru is a diamagnet displaying metallic electrical resistivity. [ABSTRACT FROM AUTHOR]

Buckybowls have unique properties that can be tailored by embedding main‐group elements into their π‐scaffolds. Herein, a synthetic approach is developed for producing monoazadichalcogenasumanenes (4 a/4 b, 6 a/6 b, 7 a/7 b) derived from sumanene by replacing its three benzylic carbons with one nitrogen and two chalcogen atoms (S for 4 a/4 b, Se for 6 a/6 b, Te for 7 a/7 b). Monoazadichalcogenasumanenes are deeper π‐bowls than trichalcogensumanenes as the C−N bond is much shorter than C−X (X=S, Se, Te). The bowl‐depth of 4 b (0.95 Å) is greater than that of corannulene (0.85 Å). The nitrogen atom donates electron density to the entire π‐system that makes monoazadichalcogenasumanenes electron‐rich. They undergo ring reconstruction of chalcogenophene ring via transferring a chalcogen atom from one molecule to another under acidic conditions. The nitrogen and chalcogen atoms play crucial role on this reaction. [ABSTRACT FROM AUTHOR]

Herein, we report a novel method for the synthesis of metallabenzenes by swapping the phosphorus atom in an aromatic phosphinine ring with transition metal fragments. The oxidation of a phosphine‐phosphinine‐phosphine pincer iridium complex by O2 triggered the replacement of the phosphorus atom of the phosphinine ring by an iridium fragment to afford iridabenzene. Dianionic rhodabenzene was also synthesized from a phosphinine rhodium complex by oxidation of the phosphorus atom, followed by subsequent reduction using metallic potassium. The aromaticity of the newly synthesized irida‐ and rhoda‐benzenes was evaluated both experimentally and theoretically. [ABSTRACT FROM AUTHOR]

The coordination chemistry of Fe2+ ions in combination with a monodentate siloxide ligand Ph3SiO− (L) was investigated. Using a Fe/L stoichiometry of 1 : 3 the complex [Na(DME)][FeL3], 2, with the iron center in a trigonal ligand environment was isolated and through decreasing the siloxide amount fraction 2 was shown to form via a unique example of a dinuclear complex, where one of the iron ions has a quasi‐trigonal and the other one a tetrahedral coordination sphere, namely [Na(DME)][Fe2L5], 1. If, however, 4 equivalents of L are employed, the tetrasiloxido ferrate(II) anion with a tetrahedral structure is generated, so that the product [Na(DME)]2[FeL4], 3, can be isolated. 2 reacts instantly with O‐atom transfer reagents, also at low temperatures, but no reaction intermediate could be identified. From the product mixture the iron(III) siloxide complex [Na(DME)3][FeL4], 4, could isolated by crystallization as the main product. Likewise, the reaction with dioxygen proceeded rather fast and added substrates did not intercept any intermediate upon its formation. However, in the presence of cyclohexene oxidation products were observed. They correspond to the typical radical‐chain‐derived products of cyclohexene suggesting, that initially a reactive FeOx species is generated that via an H atom abstraction from cyclohexene triggers its autoxidation. [ABSTRACT FROM AUTHOR]

The electrochemical performance of lithium‐sulfur (Li‐S) batteries is severely hindered by the sluggish sulfur redox kinetics and the shuttle effect of lithium polysulfides (LiPSs). Herein, an integrated composite catalyst consisting of Co nanoparticles and single‐atom (SA) Zn co‐implanted in nitrogen‐doped porous carbon nanosheets grafted with carbon nanotubes (Co/SA‐Zn@N‐C/CNTs) is rationally developed toward this challenge. Experimental and theoretical investigations indicate that the synergistically dual active sites of Co and atomic Zn‐N4 moieties with an optimal charge redistribution not only strongly confine the LiPSs but also effectively catalyze its conversion reactions by lowering the energy barrier from Li2S2 to Li2S while the N‐doped porous carbon‐grafted CNTs enables a large surface area for more active site exposure and provides a fast electron/ion pathway. Benefiting from synergies, Li‐S batteries equipped with the Co/SA‐Zn@N‐C/CNTs‐based sulfur cathode exhibit a high reversible capacity of 1302 mAh g−1 at 0.2 C and a low capacity fading rate of 0.033% per cycle over 800 cycles at 1 C. Moreover, a high areal capacity of 4.5 mAh cm−2 at 0.2 C with the sulfur loading of 5.1 mg cm−2 can be achieved. The present work may provide new insight into the design of high‐performance sulfur‐based cathodes for Li‐S batteries. [ABSTRACT FROM AUTHOR]

The rational design of single‐atom catalysts featuring excellent conductivity, highly accessible discrete active sites and favorable mass transfer is crucial for electrocatalysis but remains challenging. In this study, a reliable Ni‐catalyzed and Ni‐templated strategy is developed to synthesize a single‐atom catalyst by transforming metallic Ni into single‐Ni atoms anchored on hollow porous urchin‐like (HPU) N‐doped carbon (NC) (designated as Ni‐NC(HPU)), which possesses high crystallinity and sufficient Ni‐N4 moiety (2.4 wt %). The unique hollow thorns on the surface, good conductivity and large external surface area facilitate electron/mass transfer and exposure of single‐Ni sites. As a result, the Ni‐NC(HPU) catalyst exhibits remarkable activity and high stability for CO2 electroreduction. Moreover, this synthetic strategy can also be facilely extended to prepare distinct hollow porous architectures with similar components, such as the wire‐ and sphere‐like ones. [ABSTRACT FROM AUTHOR]

Controlling the location of aluminum atoms in a zeolite framework is critical for understanding structure–performance relationships of catalytic reaction systems and tailoring catalyst design. Herein, we report a strategy to preferentially relocate mordenite (MOR) framework Al atoms into the desired T3 sites by low‐pressure SiCl4 treatment (LPST). High‐field 27Al NMR was used to identify the exact location of framework Al for the MOR samples. The results indicate that 73 % of the framework Al atoms were at the T3 sites after LPST under optimal conditions, which leads to controllably generating and intensifying active sites in MOR zeolite for the dimethyl ether (DME) carbonylation reaction with higher methyl acetate (MA) selectivity and much longer lifetime (25 times). Further research reveals that the Al relocation mechanism involves simultaneous extraction, migration, and reinsertion of Al atoms from and into the parent MOR framework. This unique method is potentially applicable to other zeolites to control Al location. [ABSTRACT FROM AUTHOR]

Relativistic effects are known to alter the chemical bonds and spectroscopic properties of heavy‐element compounds. In this work, we introduce the concept of spin–orbit (SO) electronegativity of a heavy atom, as reflected by an SO‐induced change in the interatomic distance between the heavy atom (HA) and a neighboring light atom (LA). We provide a transparent interpretation of these SO effects by using the concept of spin–orbit electron deformation density (SO‐EDD). Spin–orbit coupling at the HA induces rearrangement of the electron density for the scalar‐relativistically optimized geometry that, in turn, exerts a new force on the LA. The resulting expansion or contraction of the HA−LA bond depends on the nature and electron configuration of the HA. In addition, we quantify the change in atomic electronegativity induced by SO coupling for a series of hydrides, thereby complementing the SO‐EDD picture. The trends in the SO‐induced electronegativity and the HA−LA bond length across the periodic table of elements are demonstrated and interpreted, and also linked, intuitively, with the SO‐induced NMR shielding at the LA. [ABSTRACT FROM AUTHOR]