Syntheses and Structures of Ruthenium(II) N,S‐Heterocyclic Carbene Diphosphine Complexes and their Catalytic Activity towards Transfer Hydrogenation

Phosphine exchange of [Ru^IIBr(MeCOO)(PPh₃)₂(3‐RBzTh)] (3‐RBzTh=3‐benzylbenzothiazol‐2‐ylidene) with a series of diphosphines (bis(diphenylphosphino)methane (dppm), 1,2‐bis(diphenylphosphino)ethylene (dppv), 1,1′‐bis(diphenylphosphino)ferrocene (dppf), 1,4‐bis(diphenylphosphino)butane (dppb), and 1,3‐(diphenylphosphino)propane (dppp)) gave mononuclear and neutral octahedral complexes [RuBr(MeCOO)(η²‐P₂)(3‐RBzTh)] (P₂=dppm ( 2 ), dppv ( 3 ), dppf ( 4 ), dppb ( 5 ), or dppp ( 6 )), the coordination spheres of which contained four different ligands, namely, a chelating diphosphine, carboxylate, N,S‐heterocyclic carbene (NSHC), and a bromide. Two geometric isomers of 6 ( 6a and 6 b ) have been isolated. The structures of these products, which have been elucidated by single‐crystal X‐ray crystallography, show two structural types, I and II, depending on the relative dispositions of the ligands. Type I structures contain a carbenic carbon atom trans to the oxygen atom, whereas two phosphorus atoms are trans to bromine and oxygen atoms. The type II system comprises a carbene carbon atom trans to one of the phosphorus atoms, whereas the other phosphorus is trans to the oxygen atom, with the bromine trans to the remaining oxygen atom. Complexes 2 , 3 , 4 , and 6a belong to type I, whereas 5 and 6 b are of type II. The kinetic product 6 b eventually converts into 6a upon standing. These complexes are active towards catalytic reduction of para‐methyl acetophenone by 2‐propanol at 82 °C under 1 % catalyst load giving the corresponding alcohols. The dppm complex 2 shows the good yields (91–97 %) towards selected ketones.     

A time-dependent density functional study on optical response in all-inorganic lead-halide perovskite nanostructures

Recently, all-inorganic perovskite nanostructures have become a hot research topic due to their unique optical response and novel properties. Here, we theoretically study the optical response in Cs₂PbX₄ and CsPb₂X₅ (X = Cl, Br, and I) nanostructures. First, to study the ground state, we calculate the band structures of the periodic system using the HSE06 method, which shows that all those periodic perovskites possess the direct band gaps, with distribution from 2.225 to 3.536 eV. Their valence band maximum are mainly contributed from both halogen and lead atoms, while the conduction band minimum are mainly contributed from lead atoms. Then, we study the excited state using the time-dependent density functional theory method and find that, with the increase of halogen atom radius, the photogenerated carrier concentrations in perovskite nanostructures become larger, while the surface plasmon resonance becomes localized rather than long-range. Moreover, through the analysis of photocurrent and local field enhancement, Cs₂PbX₄ and CsPb₂X₅ nanostructures exhibit nearly 40 μA photocurrent along the direction of optical polarization. Besides, by regulating the different anions, we predict that field enhancement in Cs₂PbI₄ and CsPb₂I₅ share a much stronger distribution at both the center and border parts of Pb-I planes due to localized plasmon resonance, while other perovskites are distributed at the edge parts of Pb-I planes, caused by long-range plasmon resonance. Our research shows that all-inorganic perovskite nanostructures are great candidate materials for developing optoelectronic devices working in high-frequency and high-energy regions and improving their application in sensitive detection and sensors.     

Structures,g-tensors,and hyperfine coupling constants of L-α-alanine radicals in radiation dosimetry: An ab initio molecular dynamics simulation study

Alanine is used as a transfer standard dosimeter for gamma ray and electron beam calibration. An important factor affecting its dosimetric response is humidity which can lead to errors in absorbed dose calculations. Ab initio molecular dynamics calculations were performed to determine the environmental effects on the electron paramagnetic resonance (EPR) parameters of L-α-alanine radicals in acidic and alkaline solutions. A new result, not dissimilar to the closed-shell amino acid molecule alanine, is that the non-zwitterionic form of the alanine radical is the stable form in the gas phase while the zwitterionic neutral alanine radical is not a stable structure in the gas phase. Geometric and EPR parameters of radicals in both gas and solution phases are found to be dependent on hydrogen bonding of water molecules with the polar groups and on dynamic solvation. Calculations on the optimized free radicals in the gas phase revealed that for the neutral radical, hydrogen bonding to water molecules drives a decrease in the magnitudes of g-tensor components g _xx and g _yy without affecting neither g _zz component nor the hyperfine coupling constants (HFCCs). The transfer from the gas to solution phase of the alanine radical anion is accompanied with an increase in the spin density on the carboxylic group's oxygen atoms. However, for the neutral radical, this transfer from gas to solution phase is accompanied with the decrease in the spin density on oxygen atoms. Calculated isotropic HFCCs and g-tensor of all radicals are in good agreement with experiment in both acidic and alkaline solutions.     

Synthesis of β-Ketoiminato Copper(II) Complexes and Their Use in Copper Deposition

The template synthesis of ethylenediamine ( 1 ) with 2-acetylcyclopentanone ( 2 ) and [Cu(OAc)₂ · H₂O] ( 5 ) produced [Cu(1-(2-cC₅H₆(O))C(Me)NCH₂)₂)] ( 6 ) in 82 % yield. Reaction of 5 with bis(benzoylacetone)diethylenetriamine ( 7 , = L H)^[1] gave [Cu(μ-OAc)( L )(H₂O)]₂ ( 8 ). The solid-state structures of 6 and 8 were determined confirming that 8 possesses intra- and intermolecular hydrogen bonds resulting in a dimer formation. The thermal behavior of 6 – 8 was studied by TG and TG-MS. Under oxygen CuO was formed, whereas under Ar Cu/Cu₂O ( 6 ) or Cu ( 8 ) was obtained. Complex 6 was used as CVD precursor for Cu and Cu-oxide deposition (substrate temp., 400–500 °C, N₂, 60 mL · min^–1; O₂, 60 mL · min^–1; pressure, 0.87–1.5 mbar). The as-obtained deposits show separated particles of different appearance at the substrate surface as evidenced by SEM. Non-volatile 8 was applied as spin-coating precursor for Cu and CuO formation [conc. 0.25 mol · L^–1; volume 0.2 mL; 3000 rpm; depos. time 2 min; heating rate 50 K · min^–1; holding time 60 min (Ar), 120 min (air) at 800 °C]. The samples on silicon consist of granulated particles (Ar) or are non-dense with a grainy topography (air). EDX and XPS measurements confirmed the formation of Cu (Ar) or CuO (O₂) with up to 13 mol-% C impurity.     

Preparation and Characterization of Protonated Fumaric Acid

Fumaric acid was reacted with the binary superacidic systems HF/SbF₅ and HF/AsF₅. The O,O'-diprotonated [C₄H₆O₄]²⁺([MF₆]^–)₂ (M = As, Sb) and the O-monoprotonated [C₄H₅O₄]⁺[MF₆]^– (M = As, Sb) species are formed depending on the stoichiometric ratio of the Lewis acid to fumaric acid. The colorless salts were characterized by low-temperature vibrational spectroscopy. In case of the hexafluoridoantimonates single-crystal X-ray structure analyses were carried out. The [C₄H₆O₄]²⁺([SbF₆]^–)₂ crystallizes in the monoclinic space group C2/c with four formula units per unit cell and [C₄H₅O₄]⁺[SbF₆]^– crystallizes in the triclinic space group P1 with one formula unit per unit cell. The protonation of fumaric acid does not cause a notable change of the C=C bond length. The experimental data are discussed together with quantum chemical calculations of the cations [C₄H₆O₄ · 4 HF]²⁺ and [C₄H₆O₄ · 2 H₂CO · 2 HF]²⁺.     

Synthesis and Single Crystal Structure Characterization of Dinuclear and Polymeric Mixed-ligand Coordination Compounds of Zinc(II) and Cadmium(II) with the Bridging Ligand 1,2-Bis(pyridin-4-ylmethylene)hydrazine

Three d¹⁰-transition-metal coordination compounds [Cd(tfpb)₂(4-bpmh)]_n ( 1 ), [Cd(9-aca)(NO₃)(OHCH₃)(4-bpmh)]_n ( 2 ) and [Zn₂(dpp)₄(4-bpmh)] ( 3 ) with the bridging ligand 4-bpmh were synthesized [4-bpmh = 1,2-bis(pyridin-4-ylmethylene)hydrazine, tfpb = 4,4,4-trifluoro-1-phenylbutane-1,3-dionate, 9-aca = anthracene-9-carboxylate, dpp = 1,3-diphenylpropane-1,3-dionate]. Compounds 1 – 3 were characterized by FT-IR spectroscopy, elemental analysis, and structurally authenticated by X-ray crystallography. Compounds 1 – 3 are constructed by an O,O'-donor ligand including chelating β-diketonates (tfpb, dpp) in 1 and 3 and a carboxylate ligand (9-aca) in 2 in combination with a linear neutral bidentate and bridging N-ligand (4-bpmh). The assembly and action of the bridging 4-bpmh ligand leads to one-dimensional coordination polymers in 1 , 2 and to a dinuclear coordination complex in 3 . The structures and the solid-state supramolecular interactions for studying the crystal packing fashions of 1 – 3 were analyzed. The supramolecular interactions including hydrogen bonding, C–H ··· π, π ··· π, and C–F ··· π in 1 , 2 , and 3 were founded.     

Carbene-Catalyzed Enantioselective Aromatic N-Nucleophilic Addition of Heteroarenes to Ketones

The aromatic nitrogen atoms of heteroarylaldehydes are activated by carbene catalysts to react with ketone electrophiles. Multi-functionalized cyclic N,O-acetal products are afforded in good to excellent yields and optical purities. Our reaction involves the formation of an unprecedented aza-fulvene-type acylazolium intermediate. A broad range of N-heteroaromatic aldehydes and electron-deficient ketone substrates works effectively in this transformation. Several of the chiral N,O-acetal products afforded through this protocol exhibit excellent antibacterial activities against Ralstonia solanacearum (Rs) and are valuable in the development of novel agrichemicals for plant protection.     

On the dynamic behavior of gas bubbles in an inhomogeneous standing wave

The motion of gas bubbles in an inhomogeneous standing wave is examined. The nonlinear system of equations is solved by the averaging method. Stationary solutions (bubble clusters) are found, and the conditions for their stability are established __________ Translated from Prikladnaya Mekhanika, Vol. 42, No. 5, pp. 88–94, May 2006.     

L p-Perturbations of Invariant Subbundles for Linear Systems

We use Riccati's equations and the ordinary and exponential dichotomies to get simple recurrent formulae for the asymptotic integration of linear systems subjected to L _p -perturbations with arbitrary p 1. Moreover, we establish conditions which are necessary and sufficient for the persistence of one-dimensional invariant subbundles for the linear system under L _p -perturbations. In this way, we prove the sharp nature of the well known Levinson and Hartman–Wintner asymptotic theorems.     

宝泉抽水蓄能电站岩体抗剪参数的选取

本文讨论了岩体抗剪参数C、f值的选取方法, 推导了C、f值的数字特征公式。通过对宝泉抽水蓄能电站工程岩体抗剪参数的选取, 结果表明：由于岩体抗剪参数具有随机性和模糊性, 采用随机-模糊法选取的C、f值要符合实际；文中给出的数字特征公式可对C、f值的波动性及相关性进行检验。