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•Important contribution of Pd NPs in catalytic C–C cross-coupling reactions.•MOFs as promising supports for Pd(0) catalysts.•In situ formation of Pd NPs from well defined Pd(II) ...complexes.•The role of ligands in stabilization of Pd NPs in catalytic conditions.
This review describes the recent advances in understanding of the mechanism of palladium catalyzed C–C cross-coupling reactions. The discussion is focused on the role of palladium nanoparticles (Pd NPs) in the catalytic process. In most cases, Pd NPs are not the only form of palladium present in the system, but they contribute in product formation together with other species forming “cocktail of catalysts”. The mixture of catalytically active species can be formed from two types of precursors, namely Pd NPs or Pd(II) complexes. To characterize catalytic systems based on pre-made Pd NPs we selected catalysts immobilized of MOF materials. The other part of review is devoted to the catalytic systems in which Pd NPs are formed in situ from molecular complexes. The role of non-phosphorus ligands in stabilization of Pd NPs was presented and discussed.
A vanadium(IV) pyrazolate-based open metal-organic polyhedron of V3(μ3-O)O(OH)2(μ4-BPD)1.5(μ-HCOO)3 (BDP = benzene-1,4-bipyrazolate) formulation gives rise to a porous crystal structure exhibiting ...micro and mesoporosity which is useful for selective adsorption of gases.
Nitrogen mono-oxide and sulfur dioxide can be removed by simultaneous absorption into aqueous mixed solutions of sulfite and Fe
II
(edta)H
2
O)
2−
, ferrous ion coordinated to an anion of ...ethylene-diaminetetraacetic acid (EDTA or edta). In the industrial system with coexisting oxygen in the gas phase, Fe
II
(edta)(H
2
O)
2−
complex is oxidized to Fe
III
(edta)(H
2
O)
−
by molecular oxygen. Because the ferric complex has no capability for reaction with NO, the suppression of this undesired oxidation process is a very important technological problem to be overcome. In our preceding work, we discussed the reduction kinetics of ferric ion by metal powder on the basis of the kinetic data regarding the ferric ion reduction in aqueous solutions of Fe
III
(edta)(H
2
O)
−
containing aluminum, tin or zinc powders. Zinc powder of normal size was recognized as an effective reducing agent. In the present work, augmentation of reducing capability of zinc powder was examined more. The rate of reduction of nano-size zinc powder was found to be about 11 times higher than that of normal-size zinc one.
The Cover Feature shows a symbolical train which transports new palladium‐carbon nanocatalysts obtained by thermolysis of Pd‐MOF material. The train climbs to overcome the activation barrier of the ...catalytic phenylacetylene hydrogenation. The studies were performed in Wrocław, where the characteristic buildings shown in the picture are located. In their Full Paper, A. W. Augustyniak and A. M. Trzeciak described new opportunities to use Pd(pymo)2n MOF as a platform for the fabrication of palladium nanocatalysts, highly selective in the transfer hydrogenation of alkynes to alkenes. The Pd/CPYMO converted phenylacetylene to styrene with 99% selectivity in water at 40 °C.More information can be found in the Full Paper by A. W. Augustyniak and A. M. Trzeciak..
Exclusive Formula omitted-meson electroproduction is studied by the HERMES experiment, using the 27.6 GeV longitudinally polarized electron/positron beam of HERA and a transversely polarized hydrogen ...target, in the kinematic region 1.0 GeV Formula omitted 7.0 GeV Formula omitted, 3.0 GeV Formula omitted 6.3 GeV, and Formula omitted 0.4 GeV Formula omitted. Using an unbinned maximum-likelihood method, 25 parameters are extracted. These determine the real and imaginary parts of the ratios of several helicity amplitudes describing Formula omitted-meson production by a virtual photon. The denominator of those ratios is the dominant amplitude, the nucleon-helicity-non-flip amplitude Formula omitted, which describes the production of a longitudinal Formula omitted-meson by a longitudinal virtual photon. The ratios of nucleon-helicity-non-flip amplitudes are found to be in good agreement with those from the previous HERMES analysis. The transverse target polarization allows for the first time the extraction of ratios of a number of nucleon-helicity-flip amplitudes to Formula omitted. Results obtained in a handbag approach based on generalized parton distributions taking into account the contribution from pion exchange are found to be in good agreement with these ratios. Within the model, the data favor a positive sign for the Formula omitted transition form factor. By also exploiting the longitudinal beam polarization, a total of 71 Formula omitted spin-density matrix elements is determined from the extracted 25 parameters, in contrast to only 53 elements as directly determined in earlier analyses.
The presently world largest data sample for π0→γe+e− decays studies containing nearly 5×105 events was collected using the WASA detector at COSY. A search for a dark photon U produced in the ...π0→γU→γe+e− decay from the pp→ppπ0 reaction was carried out. An upper limit on the square of the U−γ mixing strength parameter ϵ2 of 5×10−6 at 90% CL was obtained for the mass range 20 MeV<MU<100 MeV. This result together with other recent experimental limits significantly reduces the MUvs. ϵ2 parameter space which could explain the presently seen deviation between the Standard Model prediction and the direct measurement of the anomalous magnetic moment of the muon.
A binary and ternary system of highly bioactive nanoparticles of xerogel (88SiO2–12CaO (wt.%), solvXG88, 78SiO2–16CaO–6P2O5, solvXG78P6) and glass (69SiO2–25CaO–6P2O5, solvBG69P6) were prepared ...following an unconventional solvothermal path of the synthesis. These nanosized (<50 nm), non-spherical in shape and mesoporous materials with different compositions greatly enhanced the formation process of hydroxyapatite (HA) in simulated physiological fluids compared to reference 45S5 glass, commonly used in orthopedics and dentistry. The deposition of a HA layer on the glasses was analyzed by various techniques, namely XRD, IR-ATR, 31P CP-MAS NMR, EDS analyses, SEM, and HR-TEM imaging. For both types of nanoparticles (glass and obtained at lower temperature xerogels) superior apatite-mineralization ability in time as short as 4 h in the physiological-like buffer was achieved thus, exceeded the bioactivity of the 45S5 glass. This unique bioactivity was complemented by biocompatibility with human dermal fibroblasts and MC3T3 mouse osteoblast precursors, verified in a wide range of concentrations, as well as hemocompatibility studies. The most promising candidate which can compete with clinically used Bioglass is solvXG78P6.
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A comprehensive collection of results on longitudinal double-spin asymmetries is presented for charged pions and kaons produced in semi-inclusive deep-inelastic scattering of electrons and positrons ...on the proton and deuteron, based on the full HERMES data set. The dependence of the asymmetries on hadron transverse momentum and azimuthal angle extends the sensitivity to the flavor structure of the nucleon beyond the distribution functions accessible in the collinear framework. No strong dependence on those variables is observed. In addition, the hadron charge-difference asymmetry is presented, which under certain model assumptions provides access to the helicity distributions of valence quarks.
Differential cross sections have been extracted from exclusive and kinematically complete high-statistics measurements of quasifree polarized $\vec n$p scattering performed in the energy region of ...the d* (2380) dibaryon resonance covering the range of beam energies Tn = 0.98 - 1.29 GeV (√ s = 2.32 - 2.44 GeV). The experiment was carried out with the WASA-at-COSY setup having a polarized deuteron beam impinged on the hydrogen pellet target and utilizing the quasifree process dp → np + pspectator. In this way the np differential cross section σ (Θ) was measured over a large angular range. The obtained angular distributions complement the corresponding analyzing power Ay (Θ) measurements published previously. A SAID partial-wave analysis incorporating the new data strengthens the finding of a resonance pole in the coupled 3D3 - 3G3 waves.
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