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The development of ionic conductors as solid-state electrolytes to replace the widely used liquid electrolytes could effectively solve the safety issues as well as enhance the energy density of batteries. Yet no ionic conductors to date could meet all the criteria of solid-state electrolytes for practical applications. Therefore, exploration of new materials is highly demanded. Herein, a new type of metalorganic-based materials, namely, lithium indolide and its tetrahydrofuran (THF)-coordinated derivatives, are developed and employed as fast ionic conductors. Their crystal structures are also determined. Particularly, the lithium indolide ditetrahydrofuran shows ionic conductivities of 6.28 × 10

Controlling of radical reactivity by binding a radical to the metal center is an elegant strategy to overcome the challenge that radical intermediates are "too reactive to be selective". Yet, its application has seemingly been limited to a few strained-ring substrates, azide compounds, and diazo compounds. Meanwhile, first-row transition-metal-catalyzed (mainly, Fe, Ni, Cu) transformations of oxime esters have been reported recently in which the activation processes are assumed to follow free-radical mechanisms. In this work, we show by means of density functional theory calculations that the activation of oxime esters catalyzed by Fe(II) and Cu(I) catalysts more likely affords a metal-bound iminyl radical, rather than the presumed free iminyl radical, and the whole process follows a metal-bound radical mechanism. The as-formed metal-bound radical intermediates are an Fe(III)-iminyl radical (

Selective hydrogenation of alkynes to alkenes requires a catalytic site with suitable electronic properties for modulating the adsorption and conversion of alkyne, alkene as well as dihydrogen. Here, we report a complex palladium hydride, CaPdH2, featured by electron-rich [PdH2]δ- sites that are surrounded by Ca cations that interacts with C2H2 and C2H4 via σ-bonding to Pd and unusual cation-π interaction with Ca, resulting in a much weaker chemisorption than those of Pd metal catalysts. Concomitantly, the dissociation of H2 and hydrogenation of C2Hx (x = 2-4) species experience significant energy barriers over CaPdH2, which is fundamentally different from those reported Pd-based catalysts. Such a unique catalytic environment enables CaPdH2, the very first complex transition-metal hydride catalyst, to afford a high alkene selectivity for the semihydrogenation of alkynes.

Summary Early 3d metals such as chromium can easily dissociate N2, but the subsequent hydrogenation to ammonia is difficult because they bind nitrogen too strongly. Hence, investigation of Cr-based catalysts for ammonia synthesis is very rare. Here we show that when Cr compounds with Ba, N, and H forming a nitride-hydride, effective ammonia synthesis catalysis can be achieved under mild conditions. Under 573 K and 10 bar, this catalyst has an ammonia synthesis rate (6.8 mmolNH3 gcat−1 h−1) that is about four times that of the Cs-Ru/MgO catalyst. With low apparent activation energy (50.1 kJ mol−1) and positive reaction orders of H2 and N2, it can produce observable ammonia at 373 K and 1 bar. The active phase has a Ba5CrN4H-like structure containing reactive hydrogen ( H - ) and nitrogen, which are involved in the ammonia formation. This work discloses a strategy to “activate” the inactive early transition metals for effective ammonia catalysis.

Hydrodenitrogenation (HDN) of nitrogen-containing organic compounds such as aniline and its derivatives is of scientific interest and practical importance. Major efforts have been devoted to the development and understanding of transition metal-mediated chemical processes. Herein, we report a fundamentally different strategy using a transition metal-free material, that is, lithium hydride (LiH) enabling the hydrogenolysis of aniline to benzene and ammonia via a chemical looping approach. Aniline reacts with LiH to form lithium anilide, and subsequently, the hydrogenolysis of lithium anilide yields benzene and ammonia and regenerates LiH to complete the loop. This LiH-mediated chemical looping HDN process stands in sharp contrast to the transition metal-catalyzed or -mediated processes, which commonly lead to the complete hydrogenation of aromatic rings. A highly denitrogenated product formation rate of 2623 μmol·g

In this study, we present a new hybrid functional denoted as xOPBE, which is optimized at the 6-311+G(2d,p) basis set and designed with a specific aim of providing accurate 13C chemical shifts. By mixing the Hartree-Fock exchange into the OPBE functional, xOPBE provides a significantly improved overall performance as compared to its parent OPBE functional, while OPBE was shown previously as an excellent functional for 13C chemical shifts. Even in the case of the 1-adamantyl cation, for which OPBE completely fails in reproducing the experimental results, xOPBE still performs very well with similar accuracy as the standard CCSD(T) method with a large basis set. Our results also demonstrate that xOPBE not only can improve quantitatively the description of the correct assignments given by OPBE but also can revert OPBE's incorrect assignments qualitatively. Thus, we would like to recommend the use of xOPBE for routine evaluations of 13C chemical shifts.

Storing hydrogen efficiently in condensed materials is a key technical challenge. Tremendous efforts have been given to inorganic hydrides containing B–H, Al–H and/or N–H bonds, while organic compounds with a great variety and rich chemistry in manipulating C–H and unsaturated bonds, however, are undervalued mainly because of their unfavourable thermodynamics and selectivity in dehydrogenation. Here, we developed a new family of hydrogen storage material spanning across the domain of inorganic and organic hydrogenous compounds, namely metallo-N-heterocycles, utilizing the electron donating nature of alkali or alkaline earth metals to tune the electron densities of N-heterocyclic molecules to be suitable for hydrogen storage in terms of thermodynamic properties. Theoretical calculations reveal that the enthalpies of dehydrogenation (ΔHd) of these metallo-N-heterocycles are dependent on the electronegativity of the metals. In line with our calculation results, sodium and lithium analogues of pyrrolides, imidazolides and carbazolides of distinct structures were synthesized and characterized for the first time, where the cation-π interaction was identified. More importantly, a reversible hydrogen absorption and desorption can be achieved over lithium carbazolide which has a hydrogen capacity as high as 6.5 ​wt% and a suitable enthalpy of dehydrogenation of 34.2 ​kJ ​mol−1-H2 for on-board hydrogen storage.

The natural DNA double helix consists of two strands of nucleotides that are held together by multiple hydrogen bonds. Here we propose to build an artificial double helix from fragments of two strands connected by covalent linkages therein, but with halogen bonding as the driving force for self-assembling the fragments to the double helix. We succeed in building such a double helix in both solution and solid state, by using a bilateral N-(p-iodobenzoyl)alanine based amidothiourea which in its folded cis-form allows double and crossed C−I···S halogen bonds that lead to right- or left-handed double helix when the two alanine residues are of the same L,L- or D,D-configuration. The double helix forms in dilute CH3CN solution of the micromolar concentration level, e.g., 5.6 μM from 2D NOESY experiments and exhibits a high thermal stability in solution up to 75 °C, suggesting cooperative and thereby strong intermolecular double crossed halogen bonding that makes the double helix stable. This is supported by the observed homochiral self-sorting in solution., Building an artificial double helix is a compelling challenge, and most strategies rely on the intertwining of two helical strands. Here, in a very different approach, the authors construct a supramolecular double helix from multiple synthetic small molecules chained together by double crossed halogen bonds.

Hydrogen uptake and release in arene-cycloalkane pairs provide an attractive opportunity for on-board and off-board hydrogen storage. However, the efficiency of arene-cycloalkane pairs currently is limited by unfavorable thermodynamics for hydrogen release. It is shown here that the thermodynamics can be optimized by replacement of H in the -OH group of cyclohexanol and phenol with alkali or alkaline earth metals. The enthalpy change upon dehydrogenation decreases substantially, which correlates with the delocalization of the oxygen electron to the benzene ring in phenoxides. Theoretical calculations reveal that replacement of H with a metal leads to a reduction of the HOMO-LUMO energy gap and elongation of the C-H bond in the α site in cyclohexanolate, which indicates that the cyclohexanol is activated upon metal substitution. The experimental results demonstrate that sodium phenoxide-cyclohexanolate, an air- and water-stable pair, can desorb hydrogen at ca. 413 K and 373 K in the solid form and in an aqueous solution, respectively. Hydrogenation, on the other hand, is accomplished at temperatures as low as 303 K.

Gold-catalyzed intermolecular alkyne oxidation has attracted much synthetic attention, but mostly suffering undesired over-oxidation. Recent experiments demonstrated that over-oxidation could be dramatically suppressed in zinc(II)-catalyzed intermolecular alkyne oxidation/CH functionalization. By means of first-principle density functional theory calculations, we explored the mechanism of the M-catalyzed intermolecular alkyne oxidations (M = Zn(OTf)2 and Au+ PR3 ) as well as the effects of oxidants, temperature, and metal catalysts on chemoselectivity, in an effort to disclose the origin of the extraordinary chemoselectivity pertaining to zinc catalysis. Our calculations indicate that the Zn-catalyzed intermolecular alkyne oxidation/CH functionalization proceeds by a Friedel-Crafts alkylation mechanism rather than metal carbene insertion mechanism. The chemoselectivity of CH functionalization against over-oxidation in Zn catalysis, in comparison with gold catalysis, can be jointly controlled by four factors: (1) the use of less nucleophilic N-oxide, (2) the enhanced electrophilicity and carbocationic nature of the carbenic site in the α-oxo metal carbenoid intermediate, (3) enhanced steric repulsion to incoming oxidant exerted by bulky ancillary ligand in the close nearby of the carbenic site to disfavor intermolecular over-oxidation and (4) the large negative value of activation entropy in the intermolecular over-oxidation pathway, that jointly give rise to lower activation free energy for the intramolecular cyclization/CH functionalization pathway than for the intermolecular over-oxidation pathway. © 2018 Wiley Periodicals, Inc.

Background: During the biomass-to-bio-oil conversion process, many researches focus on the study of the association between the biomass and the bio-products by using near infrared spectra (NIR) and chemical analysis method. However, the characterization of biomass pyrolysis behaviors by using thermogravimetric analysis (TGA) with support vector machine (SVM) algorithm has not been reported. In this study, tobacco was chosen as the object for biomass, because the cigarette smoke (including water, tar and gases) released by tobacco pyrolysis reactions decide the sensory quality, which is similar to the use of biomass as a renewable resource through the pyrolysis process. Results: Support vector machine (SVM) has been employed to automatically classify the planting area and growing position of tobacco leaves by using thermogravimetric analysis data as the information source for the first time. 88 single-grade tobacco samples belonging to 4 grades and 8 categories were split into the training, validation and blind testing set. Our model showed excellent performances in both the training and validation set as well as in the blind test, with accuracy over 91.67%. Throughout the whole dataset of 88 samples, our model not only provides precise results on the planting area of tobacco leave, but also accurately distinguishes the major grades among the upper, lower and middle positions. Error only occurs in the classification of subgrades of the middle position. Conclusions: Our results not only validated the feasibility of using thermogravimetric analysis with SVM algorithm as an objective and rapid method for automatic classification of tobacco planting area and growing position, but also showed this new analysis method would be a promising way to exploring bio-oil quality prior to biomass pyrolysis production.

Background During the biomass-to-bio-oil conversion process, many studies focus on studying the association between biomass and bio-products using near-infrared spectra (NIR) and chemical analysis methods. However, the characterization of biomass pyrolysis behaviors using thermogravimetric analysis (TGA) with support vector machine (SVM) algorithm has not been reported. In this study, tobacco was chosen as the object for biomass, because the cigarette smoke (including water, tar, and gases) released by tobacco pyrolysis reactions decides the sensory quality, which is similar to biomass as a renewable resource through the pyrolysis process. Results SVM algorithm has been employed to automatically classify the planting area and growing position of tobacco leaves using thermogravimetric analysis data as the information source for the first time. Eighty-eight single-grade tobacco samples belonging to four grades and eight categories were split into the training, validation, and blind testing sets. Our model showed excellent performances in both the training and validation set as well as in the blind test, with accuracy over 91.67%. Throughout the whole dataset of 88 samples, our model not only provides precise results on the planting area of tobacco leave, but also accurately distinguishes the major grades among the upper, lower, and middle positions. The error only occurs in the classification of subgrades of the middle position. Conclusions From the case study of tobacco, our results validated the feasibility of using TGA with SVM algorithm as an objective and fast method for auto-classification of tobacco planting area and growing position. In view of the high similarity between tobacco and other biomasses in the compositions and pyrolysis behaviors, this new protocol, which couples the TGA data with SVM algorithm, can potentially be extrapolated to the auto-classification of other biomass types.

In this study, we present a new hybrid functional denoted as xOPBE, which is optimized at the 6-311+G(2d,p) basis set and designed with a specific aim of providing accurate

Research on hydraulic fracture initiation and vertical propagationbehavior in laminated tight formationAnan Wu1, Bing Hou*1, Fei Gao2，Yifan Dai1，Mian Chen1(1. State Key Laboratory of Petroleum Resources and Engineering, China University of Petroleum-Beijing, Beijing, China No.1 Cementing Company, Bohai Drilling Engineering Company Limited, CNPC, China. Renqiu,062550) Abstract: The extent of hydraulic fracture vertical propagation extent is important in evaluating simulated reservoir volume for laminated tight reservoirs. Given that it is affected by the discontinuities (beddings, natural fractures, and other factors), fracture geometry is complex in the vertical plane and is different from a simple fracture in a homogeneous formation. Because the tight formation bedding is very developed, hydraulic fracture is difficult to spread vertically. Now,the propagation mechanism of hydraulic fracture in the vertical plane has not been well understood. To clarify this mechanism, several groups of large-scale tri-axial tests were deployed in this study to investigate the fracture initiation and vertical propagation behavior in laminated tight formation. The influences of multiple factors on fracture vertical propagation were studied.we carried out the indoor hadraulic fracturing physical simulation experiments of the bedding-developed rocks. Tight cores obtained from the core well were wrapped with cement into 30 cm cubes, and samples were drilled and cemented. Before the experiment ,three-dimensional axial stress was applied to simulate the stratigraphic environment. When the stress was balanced, a certain flowing rate was set for hadraulic fracturing. After the fracturing work was completed, the cement block was opened to observe the hydraulic fracture propagation pattern.The results showed that the ultimate fracture geometries could be classified into three categories: simple bedding fracture, slight turning fracture, stair-like fracture, and multilateral fishbone-like fracture network. Here comes some research knowledge:(1)When the difference between the vertical stress and the minimum horizontal principal stress is less than 12Mpa, the hydraulic fracture will only expand along the rock bedding plane Furthermore. (2)when the vertical stress difference is close to 14 MPa, hydraulic fractures will generate vertical fractures that will communicate multiple beddings of the rock. (3)Increasing flowing rate will cause a slight turning or jumping fractures and improve the complexity of fractures to a certain extent. (4)because of the influence of beddings and lithology,the fracture pressure is usually high.Key words: Hydraulic fracturing, tight reversior Bedding plane, fracture morphology.

The lack of efficient hydrogen storage material is one of the bottlenecks for the large-scale implementation of hydrogen energy. Here, a series of new hydrogen storage materials, i.e., anilinide–cyclohexylamide pairs, are proposed via the metallation of an aniline–cyclohexylamine pair. DFT calculations show that the enthalpy change of hydrogen desorption (ΔHd) can be significantly tuned from 60.0 kJ per mol-H2 for the pristine aniline–cyclohexylamine pair to 42.2 kJ per mol-H2 for sodium anilinide–cyclohexylamide and 38.7 kJ per mol-H2 for potassium anilinide–cyclohexylamide, where an interesting correlation between the electronegativity of the metal and the ΔHd was observed. Experimentally, the sodium anilinide–cyclohexylamide pair was successfully synthesised with a theoretical hydrogen capacity of 4.9 wt%, and the hydrogenation and dehydrogenation cycle can be achieved at a relatively low temperature of 150 °C in the presence of commercial catalysts, in clear contrast to the pristine aniline–cyclohexylamine pair which undergoes dehydrogenation at elevated temperatures.

Fatty acid photodecarboxylase (FAP), was reported recently that can catalyze fatty acid decarboxylation to afford n-alkanes in blue light. A trimolecular photocycle mechanism involving an unidentified proton donor HX was proposed, which is seemingly incompatible with the observed high quantum yield (>80%). Herein, we present an energetic preferred bimolecular mechanism by DFT that involves FADH-based intermediates. Our present work suggests that the light-capturing organic molecule itself, lumiflavin (FI) of FAD, may act as a metal-free photocatalyst for the photodecarboxylation of fatty acids to afford hydrocarbons in organic synthesis.

The development of cost-effective and highly efficient catalysts is of scientific importance and practical need in the conversion and utilization of clean energy. One of the strategies fulfilling that demand is to achieve high exposure of a catalytically functional noble metal to reactants to maximize its utilization efficiency. We report herein that the single-atom alloy (SAA) made of atomically dispersed Pt on the surface of Ni particles (Pt is surrounded by Ni atoms) exhibits improved catalytic activity on the hydrolytic dehydrogenation of ammonia–borane, a promising hydrogen storage method for onboard applications. Specifically, an addition of 160 ppm of Pt leads to ca. 3-fold activity improvement in comparison to that of pristine Ni/CNT catalyst. The turnover frequency based on the isolated Pt is 12000 molH2 molPt–1 min–1, which is about 21 times the value of the best Pt-based catalyst ever reported. Our simulation results indicate that the high activity achieved stems from the synergistic effect bet...

In this work, we present an alternative mechanism without the initial coordination of reactant and catalyst for the asymmetric Henry reaction over Cu(II) catalyst. Our calculations show that the re-coordination of acetate and Cu center is essential for the enantioselectivity. Thus, any effect of the re-coordination process would affect the enantioselectivity for this reaction.

A series of chiral and achiral neutral vanadyl complexes with N - heterocycle chelated ligands [V 2 O 2 ( S -lact) 2 (bpy) 2 ] ( 1 ), [V 2 O 2 ( S -lact) 2 (phen) 2 ] ( 2 ), [V 2 O 2 ( R -lact)( S -lact)(bpy) 2 ] ( 3 ), [V 2 O 2 ( R -lact)( S -lact)(phen) 2 ] ( 4 ) (H 2 lact = lactic acid, phen = 1,10-phenanthroline, and bpy = 2,2′-bipyridine) have been obtained under hydrothermal condition. The complexes feature bidentate lactate that chelates to vanadium atom through their α-alkoxido and carboxylato groups, while the other coordination sites are occupied by N - heterocycle ligand and terminal oxygen without coordinated or crystallized water molecule. Unusual short bond distances are observed for the coordinated lactates with V (IV) –O α-alkoxy and V (IV) –O carboxy 1.986(7) A in average, which imply the influence of full deprotonation in the chelated ring compared with those of 2.15 A in iron vanadium cofactor of V-nitrogenase. Enhanced activity and the red-shifts of vibrational circular dichroism (VCD) have been observed for the chiral neutral vanadyl complexes 1 and 2 and supported by B3LYP calculation. The carboxylato vibrations in VCD are observed in 1660, 1649, 1600, 1474, 1443 cm −1 and 1664, 1653, 1636, 1483, 1431 cm −1 for 1 and 2 respectively. Their absolute configurations of chiral metal center are assigned as Λ S . The EPR spectra of 1 and 3 with bpy ligands appear to be isotropic, while 2 and 4 with phen ligands display textbook rhombic EPR spectra, and the g values obtained are g xx 2.4727, g yy 1.9975, g zz 1.6456 for 2 ; and g xx 2.4585, g yy 1.9976, g zz 1.6412 for 4 respectively.

Au-catalyzed propargyl ester reactions have been investigated by a comprehensive density functional theory (DFT) study. Our calculations explain the experimental observed chemoselectivity of Au-catalyzed propargyl ester reactions very well by considering all possible pathways both in the absence and presence of 1,2,3-triazole (TA). The “X-factor” of TA is disclosed to have triple effects on this reaction. First of all, it can stabilize and prevent rapid decomposition of the Au catalyst. Secondly, the existence of TA promotes the nucleophilic attack and alters the chemoselectivity of this reaction. Moreover, TA acts as a “relay” to promote the proton transfer.

Previously, we have proposed a method, FPA-M, for focal-point analysis of magnetic parameter calculations [Sun et al., J. Chem. Phys. 138, 124113 (2013)], where the shielding constants at equilibrium geometries σe are calculated with the second order Moller-Plesset perturbation (MP2) approach, which are extrapolated to the complete basis set (CBS) limit and then augmented by the [σe(CCSD(T)) − σe(MP2)] difference at a valence triple-ζ (VTZ) basis set, where CCSD(T) stands for the coupled cluster singles and doubles model with a perturbative correction for triple excitations. This FPA-M(MP2) method provides satisfactory results to approach to the corresponding CCSD(T)/CBS values for elements of the first two rows in the periodic tables. A series of extensions have been explored here, which replace the MP2/CBS with the Hartree-Fock (HF)/CBS for efficiency. In particular, the [σe(CCSD(T)) − σe(MP2)] VTZ difference is replaced by a step-wise correction from the [σe(CCSD(T)) − σe(MP2)] difference at a valence double-ζ basis set plus the [σe(MP2) − σe(HF)] VTZ difference, leading to a new scheme, denoted here as FPA-M(HF′). A systematical comparison has demonstrated that the FPA-M(HF′) method provides an excellent balance between accuracy and efficiency, which makes routinely accurate calculations of the shielding constants for medium-sized organic molecules and biomolecules feasible.

Alkali metals have been widely employed as catalyst promoters; however, the promoting mechanism remains essentially unclear. Li, when in the imide form, is shown to synergize with 3d transition metals or their nitrides TM(N) spreading from Ti to Cu, leading to universal and unprecedentedly high catalytic activities in NH3 decomposition, among which Li2NH-MnN has an activity superior to that of the highly active Ru/carbon nanotube catalyst. The catalysis is fulfilled via the two-step cycle comprising: 1) the reaction of Li2NH and 3d TM(N) to form ternary nitride of LiTMN and H2, and 2) the ammoniation of LiTMN to Li2NH, TM(N) and N2 resulting in the neat reaction of 2 NH3⇌N2+3 H2. Li2NH, as an NH3 transmitting agent, favors the formation of higher N-content intermediate (LiTMN), where Li executes inductive effect to stabilize the TM-N bonding and thus alters the reaction energetics.

LiNH2 decomposes to NH3 rather than N2 and H2 because of a severe kinetic barrier in NHx (x = 1, 2) coupling. In the presence of Ru, however, a drastic enhancement in N2 and H2 formation is obtained, which enables the LiNH2-Ru composite to act as a highly active catalyst for NH3 decomposition. Experimental and theoretical investigations indicate that Li creates a NHx-rich environment and Ru mediates the electron transfer facilitating NHx coupling. A strategy in catalytic material design is thus proposed.

Borohydrides have been recently hightlighted as prospective new materials due to their high gravimetric capacities for hydrogen storage. It is, therefore, important to understand the underlying dehydrogenation mechanisms for further development of these materials. We present a systematic theoretical investigation on the dehydrogenation mechanisms of the Mg2(BH4)2(NH2)2 compounds. We found that dehydrogenation takes place most likely via the intermolecular process, which is favorable both kinetically and thermodynamically in comparison with that of the intramolecular process. The dehydrogenation of Mg2(BH4)2(NH2)2 initially takes place via the direct combination of the hydridic H in BH4− and the protic H in NH2−, followed by the formation of Mg—H and subsequent ionic recombination of Mg—Hδ− ··· Hδ+−N.

Calculation of large complex systems remains to be a great challenge, where there is always a trade-off between accuracy and efficiency. Recently, we proposed the extended our own n-layered integrated molecular orbital (ONIOM) method (XO) (Guo, Wu, Xu, Chem. Phys. Lett. 2010, 498, 203) which surmounts some inherited limitations of the popular ONIOM method by introducing the inclusion-exclusion principle used in the fragmentation methods. The present work sets up general guidelines for the construction of a good XO scheme. In particular, force-error test is proposed to quantitatively validate the usefulness of an XO scheme, taking accuracy, efficiency and scalability all into account. Representative studies on zeolites, polypeptides and cyclodextrins have been carried out to demonstrate how to strive for high accuracy without sacrificing efficiency. As a natural extension, XO is applied to calculate the total energy, fully optimized geometry and vibrational spectra of the whole system, where ONIOM becomes inapplicable.

Benzene dimer (bz2) is the simplest prototype of the π-π interactions. Such interactions are ubiquitous in diverse areas of science and molecular engineering. In the present work, we have made assessment on some modern density functional methods including B97-D, BLYP-D3, M06–2X, XYG3, and force field models including CHARMM, AMBER, MM3, AMOEBA on six important interaction modes of bz2. Our results not only highlight the usefulness of these cost-effective methods, which can be used as economic substitutes of the expensive CCSD(T) for complex real-world systems, but also indicate their weakness in the description of the π-π interactions, which points to the future direction for further improvements.

CAS [KGCX2-YW-806, KJCX2-YW-H21, 2009AA05Z108, 2010CB631304]; US Department of Energy, Office of Science, Office of Basic Energy Sciences [DE-AC02-06CH11357]