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This work comprehensively investigated the coordination chemistry of a

Actinide (Th and U) carbides as the potential nuclear fuels in nuclear reactors require basic research in order to understand the thermodynamic stability and performance of these substances. Here we report the structural characterization and bonding analyses of [C

The separation and management of nuclear waste is one of the problems that needs to be solved urgently, so finding a new radiation-proof and durable extractant to deal with nuclear waste is a difficult but desirable task. Since the successful isolation of the first pentavalent plutonium crown ether complex recently (Wang et al.

Designing and constructing bifunctional electrocatalysts with high efficiency, high stability and low cost for overall water splitting to produce clean hydrogen fuel is attractive but highly challenging. Here we constructed puffed quaternary FexCoyNi1-x-yP nanoarrays as bifunctional electrodes for robust overall water splitting. The iron was used as the modulator to manipulate the electron density of NiCoP nanoarray, which could increase the positive charges of metal (Ni and Co) and P sites. The resultant electronic structure of FexCoyNi1-x-yP was supposed to balance the adsorption and desorption of H and accelerate the oxygen evolution reaction (OER) kinetics. Moreover, the morphological structure of FexCoyNi1-x-yP was modulated through the kinetically controlled alkaline etching by using the amphoteric features of initial FeCoNi hydroxide nanowires. The resultant puffed structure has rich porosity, cavity and defects, which benefit the exposure of more active sites and the transport of mass/ charge. As a result, the cell integrated with the puffed quaternary FexCoyNi1-x-yP nanoarrays as both the cathode and anode only requires the overpotentials of 25 and 230 mV for hydrogen evolution reaction (HER) and OER at the current density of 10 mA cm-2 in alkaline media and a cell voltage of 1.48 V to drive the overall water splitting. Moreover, the puffed FexCoyNi1-x-yP demonstrates remarkable durability for continuous electrolysis even at a large current density of 240 mA cm-2.

Studies on transuranic oxides provide a particularly valuable insight into chemical bonding in actinide compounds, in which subtle differences between metal ions and oxygen atoms are of fundamental importance for the stability of these compounds as well as their existence. In the case of neptunium, it is still mainly limited to specific Np oxide compounds without periodicity in the formation of stable structures or different oxidation states. Here, we report a systematic global minimum search of Np

The coordination number of a given element affects its behavior, and consequently, there is great interest in understanding the related chemistry, which could greatly promote the extension and development of new materials, but remains challenging. Herein, we report a new record high coordination number (CN) for actinides established in the cage-like An(BH)24 (An = Th to Cm) via using relativistic quantum chemistry methods. Analysis of U(BH)n (n = 1 to 24) confirmed these series of systems as being geometric minima, with the BH acting as a ligand located in the first shell around the uranium. In contrast, global searches revealed a low CN half-cage structure for UB24, which could be extended to the series of AnB24 materials and which prevails over the competing structural isomers, such as cages. The intrinsic geometric difference for AnB24 and An(BH)24 mainly arise from the B sp3 hybridization in borane inducing strong interactions between An 5f6d7s hybrid orbitals and B 2pz orbitals in An(BH)24 compared to that of AnB24. This fundamental trend presents a valuable insight for future experimental endeavors searching for isolable complexes with high-coordination actinide and provides details of a new structural motif of boron clusters and nanostructures.

Lanthanide oxo compounds are of vital importance in lanthanide chemistry, as well as in environmental and materials sciences. Praseodymium, as an exceptional element in lanthanides which can form a +V formal oxidation state (OSf) besides the dominant +III among the 4f-block element, displays the significant participation of the Pr 4f orbitals in bonding interactions which is commonly crucial in stabilizing the high oxidation state of Pr in PrO2+ and NPrO species. Here, we report a systematic theoretical study on the structures and stabilities of a series of XPrO (X: B, Al, C, Si, N, P, As, O, S, F, Cl) compounds along with [XPrO]+ cation (X: O, S) and [X3PrO] complexes (X: F and Cl). This work reveals that Pr is able to achieve the lowest and highest OSf and the OSf exhibits periodic variation from +I in BOPr and AlOPr to +II in SiOPr to +III in CPrO, FPrO, ClPrO and AsPrO to +IV in OPrO and SPrO and even to +V in NPrO, [OPrO]+, [SPrO]+, F3PrO and Cl3PrO. We found that the molecular structures are correlated to the Pr oxidation state due to the highly important 4f orbital in the chemical bonding of the high oxidation state compounds. Thus, not only the electronegativity of the ligand but also the quasi-degenerate Pr valence 4f orbitals, namely energetic covalency, control the oxidation state and play a fundamental role in affecting the electronic structural stability of Pr(v) compounds as well. This work demonstrates the structurally directing role of the f-orbital in the formation of the linear structure and is constructive for achieving the higher oxidation state of a given element by tuning the ligand.

Uranium(III) compounds are very reactive and exhibit a broad range of chemical-bonding tendencies owing to the spatially diffused valence orbitals of uranium. A systematic study on the geometries, electronic structures, and chemical bonding of NU-XO (X = C, N, O) is performed using relativistic quantum chemistry approaches. The NU-CO and NU-NO complexes have an end-on structure, that is, (NU) (η

As a group 12 element, mercury locating at the sixth row with a valent electronic configuration of 5 d 10 6 s 2 has been treated as a main group element featuring +I and +II oxidation states for a long time. C. K. Jorgensen conjectured the existences of HgF4 and HgF6 molecules in early 1960s, where HgF4 was first synthesized in 2007, but HgF6 as the Hg(+VI) compound was less known. In this paper we explored the electronic structure and decomposition paths of HgF6 by scalar (X1C) and 2-component relativistic (X2C) density functional calculations and more accurate multi-reference NEVPT2 calculations. It is found that the HgF6 molecule, where the mercury atom presents an extraordinary high oxidation state of +VI, is protected by a considerable barrier height of about 22 kcal/mol for the decomposition into HgF4 and two isolated fluorine atoms. The results propose that HgF6 is kinetically stable and may exist under exorbitant conditions.

Oxidation state is a key chemical quantity that allows the understanding and prediction of the majority of chemical reactions; however, the main deficiency using the formal oxidation state comes from the materials containing multivalent metals. Among them, the most complicated element plutonium (Pu) is an outstanding instance. Here, we calculate the orbital occupation numbers under the frameworks of first-principles density functional theory (DFT) + U methods to quantitatively determine the Pu-oxidation state of the recently reported complex molecular solids: [K(crypt)]Pu[C5H3(SiMe3)2]3, Pu3(DPA)5(H2O)2, and Pu3(DPA)6H. The results show that the oxidation state of Pu is an extremely low Pu2+ in the former and a mixed Pu3+/Pu4+ in the latter two compounds, which is consistent with the experimental identifications. The steric effects and the environmentally sensitive localization → delocalization transition of Pu 5f electrons can rationally elucidate the formation of the unusual oxidation states. Such atomi...

The classic Fokin mechanism of the CuAAC reaction of terminal alkynes using a variety of Cu(I) catalysts is well-known to include alkyne deprotonation involving a bimetallic σ,π-alkynyl intermediate. In this study, we have designed a CNT-supported atomically precise nanocluster Au

Actinide metal oxo clusters are of vital importance in actinide chemistry, as well as in environmental and materials sciences. They are ubiquitous in both aqueous and nonaqueous phases and play key roles in nuclear materials (e.g., nuclear fuel) and nuclear waste management. Despite their importance, our structural understanding of the actinide metal oxo clusters, particularly the transuranic ones, is very limited because of experimental challenges such as high radioactivity. Herein we report a systematic theoretical study on the structures and stabilities of seven actinide metal oxo-hydroxo clusters [An

Despite the chemistry of actinide-ligand bonding is continuing and of burgeoning interest, investigations of the chemical bonding of bimetallic complexes involving transuranics remain relatively less, and there are rarely studies on the bonding features between actinide and coinage metals (CM). We present a systematic research on the series of An@Au

Despite continuing and burgeoning interest in f-block complexes and their bonding chemistry in recent years, investigations of the electronic structures and oxidation states of heterobimetallic complexes, and their bonding features between transition-metals (TMs) and f-elements remain relatively less explored. Here, we report a quantum chemical computational study on the series of TM-actinide and -neodymium complexes [TMAn(L)] and [TMNd(L)] [An = U, Np, Pu; TM = Cr, Mn, Fe; L = {N(o-[NCH2P(CH3)2]C6H4)3}3-] in order to explore periodic trend, generalities and differences in the electronic structure and metal-metal bonding between f-block and d-block elements. Based on the calculations, we find up to five-fold covalent multiple bonding between actinide and transition metal ions, which is in sharp contrast with a single bond between neodymium and transition metals. From a comparative study, a general trend of strength of the An-TM interaction emerges in accordance with the atomic number of the actinide metal, which relates to the nature, energy level, and spatial arrangement of their frontier orbitals. The trend presents a valuable insight for future experimental endeavour searching for isolable complexes with strong and multiple An-TM bonding interactions, especially for the experimentally challenging transuranic elements that require targeted research due to their radioactive nature.

The following gas-phase uranyl/12-crown-4 (12C4) complexes were synthesized by electrospray ionization: [UO2(12C4)2]2+ and [UO2(12C4)2(OH)]+. Collision-induced dissociation (CID) of the dication resulted in [UO2(12C4-H)]+ (12C4-H is a 12C4 that has lost one H), which spontaneously adds water to yield [UO2(12C4-H)(H2O)]+. The latter has the same composition as complex [UO2(12C4)(OH)]+ produced by CID of [UO2(12C4)2(OH)]+ but exhibits different reactivity with water. The postulated structures as isomeric [UO2(12C4-H)(H2O)]+ and [UO2(12C4)(OH)]+ were confirmed by comparison of infrared multiphoton dissociation (IRMPD) spectra with computed spectra. The structure of [UO2(12C4-H)]+ corresponds to cleavage of a C–O bond in the 12C4 ring, with formation of a discrete U–Oeq bond and equatorial coordination by three intact ether moieties. Comparison of IRMPD and computed IR spectra furthermore enabled assignment of the structures of the other complexes. Theoretical studies of the chemical bonding features of the complexes provide an understanding of their stabilities and reactivities. The results reveal bonding and structures of the uranyl/12C4 complexes and demonstrate the synthesis and identification of two different isomers of gas-phase uranyl coordination complexes.

Bismuth oxyhalides (BiOX, X = Cl, Br, and I) are a new family of promising photocatalysts. BiOCl and BiOBr possess large band gaps and weak absorption in visible light regions, which limit their applications. Although the band gap of BiOI is suitable to absorb most of the visible light, its redox capability is very weak. In this work, the doping and strain effects on the electronic structures and optical properties of BiOCl are explored using first principle calculations. The results show that doping in BiOCl, especially co-doping of Sb and I atoms, can obviously decrease the band gaps along with enhancing the optical absorption coefficients of pristine BiOCl because of the electronegativity difference between Sb/I atoms and Bi/Cl atoms. Meanwhile the band gap of BiOCl can be tuned under strain. This work offers potential strategies to enhance BiOCl absorption coefficients in the visible light region and its photocatalyst activity.

© The Royal Society of Chemistry 2016. Understanding of the nature and extent of chemical bonding in uranyl coordination complexes is crucial for the design of new ligands for nuclear waste separation, uranium extraction from seawater, and other applications. We report here the synthesis, infrared spectroscopic characterization, and quantum chemical studies of a molecular uranyl-di-15-crown-5 complex. The structure and bonding of this unique complex featuring a distinctive 6-fold coplanar coordination staggered sandwich structure and an unusual non-perpendicular orientation of the uranyl moiety are evaluated using density functional theory and chemical bonding analyses. The results provide fundamental understanding of the coordination interaction of uranyl with oxygen-donor ligands.

As B12 clusters exhibit significant structural stability due to double aromaticity, metal doped-B12 clusters often prefer a half sandwich structure. Herein, we report a systematic theoretical study on the geometric and electronic structures, and chemical bonding of the half sandwich AnB12 (An = Th to Cm) clusters to explore the stability and extent of covalency of the An-B bonds of these actinide borides. We have shown that in the gas-phase clusters, the significant stability of AnB12 is determined by electrostatic and orbital interactions between the An 5f6d7s orbitals and π-type molecular orbitals from B 2p orbitals of the B12 unit. A change-over of An-B bond length from An = Th to Cm is found at An = Pa as a result of actinide contraction combined with weakening An-B bonding due to an energy decrease and orbital localization of the 5f orbitals. Consistently, the oxidation states of the An atoms at first increase from Th(f0)IV to Pa(f0)V, and then due to the 5f-AO contraction, they smoothly decline to U(f2)IV, Np(f4)III and Pu(f5)III, and then eventually to Am(f7)II but Cm(f7)III, both with a half-filled 5f shell.

The structural and electronic properties of Pu

Recently an all-metal aromatic sandwich compound of a [Sb3Au3Sb3](3-) ion has been synthesized and characterized experimentally, which indicates that there might exist a variety of stable all-metal sandwich complexes. The intralayer and interlayer chemical bonding interaction in this system plays significant roles in their stability, chemical properties and functionalities. Here we report a systematic theoretical study on the geometries, electronic structures, and chemical bonding of the [Sb3Au3Sb3](3-) ion and its congeners of [X3Au3X3](3-) (X = N, P, As, Sb, Bi, Uup) as well as [X3M3X3](3-) (M, X = Cu, As; Ag, Bi; Au, Sb; Rg, Uup) to understand the special stabilities of these species. Additional studies are also performed on the oligomers [Sb3(Au3Sb3)n](3-) (n = 1-4) to explore whether the sandwich compound can form stable extended systems. Through extensive theoretical analyses, we have shown that among the [Au3X6](3-) (X = N, P, As, Sb, Bi, Uup) species, [Sb3Au3Sb3](3-) is most stable due to superb matching of Sb3 and Au3 in both geometric size and fragment orbital energies. The significant stability of the [Au3Sb6](3-) ion is determined by the interlayer (p-d-p)σ interactions between the vertical Au 5d6s hybrid orbitals of Au3 and Sb 5pπ orbitals of the Sb3 rings. Each Sb3 ring demonstrates unique σ aromaticity, which remains when the complex is extended to oligomers. The results suggest that it is likely that there might exist other stable [ApMpAp](x-) (M = transition metals, A = main group elements, p = 3, 4, 5, …) sandwich ions and oligomers.

For further fundamental understanding of the nature and extent of covalency in actinyl-ligand bonding, and the benefits that this may have in the design of new ligands for nuclear waste separation, there is burgeoning interest in the nature of actinyl complexes with polydentate or multiple-point-donor ligands, such as crown ethers. There are few cases of structurally authenticated molecular actinyl-crown bonds under ambient conditions. We report here the computational characterization of AnO

Muscle contraction results in structural and morphologic changes of the related muscle. Therefore, finger flexion can be monitored from measurements of these morphologic changes. We used ultrasound imaging to record muscle activities during finger flexion and extracted features to discriminate different fingers' flexions using a support vector machine (SVM). Registration of ultrasound images before and after finger flexion was performed to generate a deformation field, from which angle features and wavelet-based features were extracted. The SVM was then used to classify the motions of different fingers. The experimental results showed that the overall mean recognition accuracy was 94.05% ± 4.10%, with the highest for the thumb (97%) and the lowest for the ring finger (92%) and the mean F value was 0.94 ± 0.02, indicating high accuracy and reliability of this method. The results suggest that the proposed method has the potential to be used as an alternative method of surface electromyography in differentiating the motions of different fingers.

Calculations using density functional theory were performed to explore the mechanisms for atmospheric degradation of isopropyl methyl methylphosphonate (IMMP). The potential energy surface profiles for OH-initiated reaction of IMMP were constructed, and all possible degradation channels were considered. Rate constants were further calculated using transition state theory. It was established from these calculations that H-abstractions from alkyl groups have much lower energy barriers than substitutions of alkoxyl groups, and four possible H-abstraction channels are competitive. Investigations into the secondary reactions under the presence of O2/NO were also performed. It is shown that O2 addition, reaction of peroxide radicals with NO to form RO radicals, and removal of ·RO are the major degradation pathways for alkyl radicals. Four selected products, CH3OP(O)(CH3)OC(O)CH3, CH3OP(O)(O)CH3, (CH3)2CHOP(O)(CH3)OH, and (CH3)2CHOP(O)(CH3)OCHO, are predicted to be the major products in this study. © 2013 Wiley Periodicals, Inc.

Xylenes are important constituents of many liquid fuels, as well as precursors of secondary organic aerosols (SOAs). To examine the mechanisms for formation of SOAs in the atmosphere, the abstraction reaction of p-xylene with OH and the secondary degradation channels of its intermediates were first and extensively investigated with density functional theory at the B3LYP/6-31+G (d, p) level. The result indicates that H-abstraction from methyl groups is a barrier-less path while that from phenyl groups require a free energy barrier of approximately 2.8 kcal mol−1. Upon formation of p-xylyl, further addition by O2 readily occurs to form peroxy radical. Subsequently, possible degradation channels for the formation of main products (p-tolualdehyde and p-quinone methide) have been determined in presence of NO. The free energy profile constructed shows that the entire reaction process is exothermic. In addition, the dipole moment of p-tolualdehyde is higher than that of p-xylene, consistent with their relative hygroscopic values. This indicates that the degradation products of p-xylene can readily immerse into the SOA phase, while p-xylene may be subject to further atmospheric degradation to form non-volatile compounds.