Interaction Of Pd Research Articles

Enhanced active site extraction from perovskite LaCoO3 using encapsulated PdO for efficient CO2 methanation

The extraction of metallic nanoparticles from perovskite-type oxides (ABO3) under mild reducing conditions is a novel way to prepare well-dispersed supported catalysts (B/AOδ). Herein, we found that the encapsulated PdO in perovskite LaCoO3 ([email protected]3) could facilitate the phase transformation of the perovskite structure at a low temperature owing to both strong H2 spillover of Pd and intimate interaction between the encapsulated PdO and LaCoO3. The pure LaCoO3 without PdO was relatively inert to CO2 hydrogenation (CO2 conversion <4%). In contrast, [email protected]3 exhibited excellent CO2 methanation performance with 62.3% CO2 conversion and >99% CH4 selectivity. The characterization results demonstrated that the catalytically active Co2C was in-situ formed by carburization of the extracted Co0 during CO2 methanation for the [email protected]3 sample. Whereas, the LaCoO3 with surface supported PdO (PdO/LaCoO3) showed a weak interaction and remained a perovskite structure with few Co2C active centers after the catalytic reaction, which was similar to the parent LaCoO3. Accordingly, the PdO/LaCoO3 showed an inferior catalytic performance with 31.8% CO2 conversion and 87.4% CH4 selectivity. Therefore, the designed encapsulation structure of PdO within perovskite is critical to extract metallic NPs from perovskite-type oxides, which has the potential to prepare other integrated nanocatalysts based on perovskite-type oxides.

Spectrophotometric Determination of Palladium(II) Ions Using a New Reagent: 4-(N’-(4-Imino-2-oxo-thiazolidine-5-ylidene)-hydrazino)-benzoic Acid (p-ITYBA)

The simple, rapid spectrophotometric method for palladium(II) ions determination using a new analytical reagent is described. The interaction of Pd(II) ions with a reagent, of the class of azolidones, 4-(N′-(4-imino-2-oxo-thiazolidine-5-ylidene)-hydrazino)-benzoic acid, in water medium results in the formation of a complex. The Pd(II)-p-ITYBA complex shows maximum absorbance at a wavelength of 450 nm. The molar absorptivity is 4.30 × 103 L·mol−1·cm−1. The optimal pH for complex formation is 7.0. The developed method has a wide linearity range of 0.64–10.64 µg·mL−1 for Pd(II). The detection limit is 0.23 µg·mL−1. It was found that Co(II), Ni(II), Zn(II), Fe(III), Cu(II), Al(III), and many anions do not interfere with the Pd(II) determination. The proposed method was tested in the analysis of model solutions and successfully applied for the determination of palladium in catalyst. The obtained results show that this method can be used for serial determinations of palladium in various objects.

The Self-Assembly of a Cyclometalated Palladium Photosensitizer into Protein-Stabilized Nanorods Triggers Drug Uptake In Vitro and In Vivo.

Enhanced passive diffusion is usually considered to be the primary cause of the enhanced cellular uptake of cyclometalated drugs because cyclometalation lowers the charge of a metal complex and increases its lipophilicity. However, in this work, monocationic cyclometalated palladium complexes [1]OAc (N^N^C^N) and [2]OAc (N^N^N^C) were found to self-assemble, in aqueous solutions, into soluble supramolecular nanorods, while their tetrapyridyl bicationic analogue [3](OAc)2 (N^N^N^N) dissolved as isolated molecules. These nanorods formed via metallophilic Pd···Pd interaction and π–π stacking and were stabilized in the cell medium by serum proteins, in the absence of which the nanorods precipitated. In cell cultures, these protein-stabilized self-assembled nanorods were responsible for the improved cellular uptake of the cyclometalated compounds, which took place via endocytosis (i.e., an active uptake pathway). In addition to triggering self-assembly, cyclometalation in [1]OAc also led to dramatically enhanced photodynamic properties under blue light irradiation. These combined penetration and photodynamic properties were observed in multicellular tumor spheroids and in a mice tumor xenograft, demonstrating that protein-stabilized nanoaggregation of cyclometalated drugs such as [1]OAc also allows efficient cellular uptake in 3D tumor models. Overall, serum proteins appear to be a major element in drug design because they strongly influence the size and bioavailability of supramolecular drug aggregates and hence their efficacy in vitro and in vivo.

Citrus Postharvest Green Mold: Recent Advances in Fungal Pathogenicity and Fruit Resistance.

As the major postharvest disease of citrus fruit, postharvest green mold is caused by the necrotrophic fungus Penicillium digitatum (Pd), which leads to huge economic losses worldwide. Fungicides are still the main method currently used to control postharvest green mold in citrus fruit storage. Investigating molecular mechanisms of plant–pathogen interactions, including pathogenicity and plant resistance, is crucial for developing novel and safer strategies for effectively controlling plant diseases. Despite fruit–pathogen interactions remaining relatively unexplored compared with well-studied leaf–pathogen interactions, progress has occurred in the citrus fruit–Pd interaction in recent years, mainly due to their genome sequencing and establishment or optimization of their genetic transformation systems. Recent advances in Pd pathogenicity on citrus fruit and fruit resistance against Pd infection are summarized in this review.

One-Pot Cross-Coupling/C-H Functionalization Reactions: Quinoline as a Substrate and Ligand through N-Pd Interaction.

Herein, we report a one-pot process that marries mechanistically distinct, traditional cross-coupling reactions with C-H functionalization using the same precatalyst. The reactions proceed in yields of up to 95%, in air, and require no extraneous ligand. The reactions are thought to be facilitated by harnessing the substrate quinoline as an N-ligand, and evidence of the palladium-quinoline interaction is provided by 1H-15N HMBC NMR spectroscopy and X-ray crystallographic structures. Application of the methodology is demonstrated by the quick formation of fluorescent, π-extended frameworks.

Interaction of Pd and Rh with ZrCeYLaO2 support during thermal aging and its effect on the CO oxidation activity

A commercial ceria–zirconia composition modified with yttrium and lanthanum oxides was studied as a support for palladium- and rhodium-containing three-way catalysts. The most attention was paid to an interaction of the supported active metals with the support under high-temperature conditions. It was found that both the metals affect noticeably the porous structure of the support and the loading of metal plays a role in this process. Moreover, oxygen storage capacity of the oxide composition was also influenced by the supported metals. Hydrothermal aging of the metal-loaded samples has decreased the oxygen storage capacity values in more than 2 times. The thermal stability of the monometallic samples was compared with bimetallic Pd–Rh catalysts prepared using a “single-source precursor” approach. The experiments were performed under prompt thermal aging conditions. It was found that monometallic Pd-only samples and bimetallic Pd–Rh samples exhibit excellent stability, while monometallic Rh-only catalysts undergo deactivation being heated up to 800 °C due to diffusion of rhodium into the bulk of the support. All the samples were additionally characterized by a diffuse reflectance UV–vis spectroscopy and a testing reaction of ethane hydrogenolysis. According to the results obtained, the character of the metal-support interaction was found to be strongly affected by the catalyst’s composition. Application of the bimetallic Pd–Rh particles of alloyed type was shown to result in the preferable location of the active components on the support’s surface, thus facilitating high activity and stability of the catalyst.

Gamma-induced changes in the optical and structural properties of palladium/polycarbonate nanocomposite membrane

Makrofol Polycarbonate (PC) is a polymeric solid-state nuclear track detector (SSNTD) by which various applications can be used in several dosimetric and industrial fields. In this work, nano-sized palladium Pd was prepared and mixed with PC (5 wt.%) to produce nanocomposite films. Samples from the Pd/PC nanocomposite films have been irradiated with gamma doses 20–300 kGy. The modification induced in the optical properties and structure of the Pd/PC nanocomposite samples due to gamma irradiation has been investigated. The increase of Urbach energy, accompanied by a decrease in energy band gap, with the gamma dose indicated that the gamma irradiation up to 300 Gy increases the intermolecular interaction of PC chains and Pd leading to an increase in the disorder in the naocomposite samples. It is well known that the nano-palladium is effective in stabilizing the PC, resulting in the enhancement in both refractive index and intrinsic viscosity with the gamma dose. This leads to a more compact structure of PC due to crosslinking. Additionally, the color sensitivity for the non-irradiated Pd/PC nanocomposite sample showed a significant behavior toward gamma radiation. The color intensity ΔE is the difference in the color between non-irradiated samples and the samples irradiated with various gamma doses. ΔE is increased by increasing the dose till 300 kGy, accompanied by an increase in the yellow color component. Finally, FTIR spectroscopy was performed on the non-irradiated and irradiated samples to correlate the induced changes in Pd/PC nanocomposite with the changes in the function groups.

Potent cyclometallated Pd(II) antitumor complexes bearing α-amino acids: synthesis, structural characterization, DNA/BSA binding, cytotoxicity and molecular dynamics simulation.

A rational approach was adopted to design high-potential metal-based antitumor agents. A series of organometallic Pd(ii) complexes with a general formula of [Pd{κ2(C,C)-[(C6H4-2)PPh2]CH(CO)C6H4Ph-4}{κ2(N,O)}] (N,O = alanine (Pd-A), valine (Pd-V), leucine (Pd-L), l-isoleucine (Pd-I) and phenylalanine (Pd-F)) were prepared by cyclopalladation of the phosphorus ylide, bridge cleavage reaction and subsequent chelation of natural α-amino acids. The complexes were fully identified using IR and multinuclear 1H, 13C, 31P NMR spectroscopic methods. X-ray crystallography exhibited that the Pd(ii) atom is located in a slightly distorted square-planar environment surrounded by C,C-orthometallated phosphorus ylide as well as NO-pendant amino acid functionality. In vitro cytotoxicity evaluation of new cyclometallated Pd(ii) complexes toward a human leukemia (K562) cancer cell line indicated promising results. The highest cytotoxic activity was discovered in the case of phenylalanine (CH2C6H5). IC50 values of this complex on a panel of human tumor cell lines representative of liver (HepG2), breast (SKBR-3), and ovarian (A2780-Resistance/Sensitive) cancers also indicated promising antitumor effects in comparison with standard cisplatin. The binding interaction ability of the phenylalanine-containing orthopalladated complex, as the most efficient compound, with calf-thymus deoxyribonucleic acid (CT-DNA) and bovine serum albumin (BSA) was investigated. UV-Vis spectroscopy, competitive emission titration, and circular dichroism (CD) techniques demonstrated the intercalative binding of the Pd(ii) complex with DNA. Molecular docking studies also fully agreed with the experimental data. Examination of the reactivity towards the protein BSA revealed that the static quenching mechanism of BSA intrinsic fluorescence by the Pd(ii) complex with a binding constant (Kb) of ∼105 is indicative of the high affinity of the complex. The competitive binding experiment using site markers with definite binding sites demonstrated that the hydrophobic cavities of site I (subdomain IIA) are responsible for the bimolecular interaction between protein BSA and the complex. Molecular docking studies effectively confirmed the significance of hydrophobic interactions in Pd(ii)-BSA binding. The results of this study could greatly contribute to exploring new potent metal-based anticancer drugs.

Investigation of the Interaction of Palladium with Potassium Tetrafluorobromate

In this investigation, the interaction of metallic palladium with potassium tetrafluorobromate was examined in open system, the reaction products were identified using X-ray phase analysis. A thermogram of the interaction of Pd with KBrF4 was obtained, the temperature range of the reaction (187.9-328°C) and the thermal effect (431.31 J/g) were determined. It was found that the fluorination process is a multi-stage process. The solubility of the obtained K2PdF6 compound in nitric and hydrochloric acids was investigated. The process of extraction of palladium from nitric acid solutions with tributyl phosphate was carried out and the influence of the concentration of palladium and the acidity of the initial solution on the distribution coefficient was investigated.

The 1,10-Phenanthroline Ligand Enhances the Antiproliferative Activity of DNA-Intercalating Thiourea-Pd(II) and -Pt(II) Complexes Against Cisplatin-Sensitive and -Resistant Human Ovarian Cancer Cell Lines.

Ovarian cancer is the most lethal gynecological malignancy, often because of the frequent insurgence of chemoresistance to the drugs currently used. Thus, new therapeutical agents are needed. We tested the toxicity of 16 new DNA-intercalating agents to cisplatin (cDDP)-sensitive human ovarian carcinoma cell lines and their resistant counterparts. The compounds were the complexes of Pt(II) or Pd(II) with bipyridyl (bipy) and phenanthrolyl (phen) and with four different thiourea ancillary ligands. Within each of the four series of complexes characterized by the same thiourea ligand, the Pd(phen) drugs invariably showed the highest anti-proliferative efficacy. This paralleled both a higher intracellular drug accumulation and a more efficient DNA intercalation than all the other metal-bidentate ligand combinations. The consequent inhibition of topoisomerase II activity led to the greatest inhibition of DNA metabolism, evidenced by the inhibition of the expression of the folate cycle enzymes and a marked perturbation of cell-cycle distribution in both cell lines. These findings indicate that the particular interaction of Pd(II) with phenanthroline confers the best pharmacokinetic and pharmacodynamic properties that make this class of DNA intercalators remarkable inhibitors, even of the resistant cell growth.

Boosting Hydrogen Production from Formic Acid over Pd Catalysts by Deposition of N-Containing Precursors on the Carbon Support

Formic acid is a promising liquid organic hydrogen carrier (LOHC) since it has relatively high hydrogen content (4.4 wt%), low inflammability, low toxicity and can be obtained from biomass or from CO2. The aim of the present research was the creation of efficient 1 wt% Pd catalysts supported on mesoporous graphitic carbon (Sibunit) for the hydrogen production from gas-phase formic acid. For this purpose, the carbon support was modified by pyrolysis of deposited precursors containing pyridinic nitrogen such as melamine (Mel), 2,2′-bipyridine (Bpy) or 1,10-phenanthroline (Phen) at 673 K. The following activity trend of the catalysts Pd/Mel/C &gt; Pd/C ~ Pd/Bpy/C &gt; Pd/Phen/C was obtained. The activity of the Pd/Mel/C catalyst was by a factor of 4 higher than the activity of the Pd/C catalyst at about 373 K and the apparent activation energy was significantly lower than those for the other catalysts (32 vs. 42–46 kJ/mol). The high activity of the melamine-based samples was explained by a high dispersion of Pd nanoparticles (~2 nm, HRTEM) and their strong electron-deficient character (XPS) provided by interaction of Pd with pyridinic nitrogen species of the support. The presented results can be used for the development of supported Pd catalysts for hydrogen production from different liquid organic hydrogen carriers.

Long-range order imposed by short-range interactions in methylammonium lead iodide: Comparing point-dipole models to machine-learning force fields

The crystal structure of the ${\mathrm{MAPbI}}_{3}$ hybrid perovskite forms an intricate electrostatic puzzle with different ordering patterns of the MA molecules at elevated temperatures. For this perovskite three published model Hamiltonians based on the point-dipole (pd) approximation combined with short-range effective interactions are compared to a recently developed machine-learning force field. A molecular order parameter is used to consistently compare the transformation of the antiferroelectric ordering in the orthorhombic phase upon raising the temperature. We show that the ground states and the order-disorder transition of the three models are completely different. Our analysis indicates that the long-range order in the low-temperature orthorhombic phase can be captured by pd-based models with a short cutoff radius, including the nearest and next-nearest neighbor molecules. By constructing effective atomic interactions the ordering can already be described within a 6 \AA{} radius. By extracting the coupling energetics of the molecules from density functional theory calculations on ${\mathrm{MA}}_{x}{\mathrm{Cs}}_{1\ensuremath{-}x}{\mathrm{PbI}}_{3}$ test systems, we show that the pd approximation holds at least for static structures. To improve the accuracy of the pd interaction an Ewald summation is applied combined with a distance dependent electronic screening function.

Black Phosphorus/Palladium Nanohybrid: Unraveling the Nature of P-Pd Interaction and Application in Selective Hydrogenation.

The burgeoning interest in two-dimensional (2D) black phosphorus (bP) contributes to the expansion of its applications in numerous fields. In the present study, 2D bP is used as a support for homogeneously dispersed palladium nanoparticles directly grown on it by a wet chemical process. Electron energy loss spectroscopy–scanning transmission electron microscopy analysis evidences a strong interaction between palladium and P atoms of the bP nanosheets. A quantitative evaluation of this interaction comes from the X-ray absorption spectroscopy measurements that show a very short Pd–P distance of 2.26 Å, proving for the first time the existence of an unprecedented Pd–P coordination bond of a covalent nature. Additionally, the average Pd–P coordination number of about 1.7 reveals that bP acts as a polydentate phosphine ligand toward the surface of the Pd atoms of the nanoparticles, thus preventing their agglomeration and inferring with structural stability. These unique properties result in a superior performance in the catalytic hydrogenation of chloronitroarenes to chloroanilines, where a higher chemoselectivity in comparison to other heterogeneous catalyst based on palladium has been observed.

From Palladium Clusters in Solutions to Supported Nanocatalysts for Hydrocarbon Synthesis

Literature data on palladium clusters obtained by the interaction of Pd(II) compounds in solutions with hydrogen are summarized and analyzed. The conclusion is drawn on the influence of ligands and reduction conditions on the polynuclearity of clusters and on the autocatalytic nature of their formation. Palladium clusters become active in the selective hydrogenation of alkynes and dienes only after their treatment with hydrogen containing traces of oxygen or hydrogen peroxide. Clusters containing phosphide ligands are active in the homogeneous hydrogenation of unsaturated hydrocarbons with a high selectivity being of a thermodynamic nature. Most of the distinctive features of nanocluster synthesis in solution are also observed in the synthesis of metal-containing nanoparticles on the support surface from precursors. Catalysts for the liquid-phase selective hydrogenation of phenylacetylene on the Pd supported on coal with a nanoparticle size of 2.8 ± 0.2 nm are obtained. This size is comparable with the size of clusters in solution. The mechanism for the reduction of palladium acetate on carbon is also autocatalytic and is similar to the same process in solutions. A kinetic study of the selective hydrogenation of phenylacetylene to styrene in the presence of Pd supported on coal shows that it is impossible to adequately describe the experimental data in the framework of the Langmuir, Hinshelwood, or Eley–Rideal mechanisms. It is proposed to use this mechanism in the framework of cluster (polynuclear) active sites on the surface of Pd particles capable of adsorbing more than one substrate molecule or its fragments on the same site. This approach makes it possible to describe the mechanisms of other reactions occurring in the presence of nanoscale heterogeneous supported catalysts: deoxygenation of fatty acids obtained from renewable raw materials to paraffins on supported palladium catalysts and olefins on supported nickel sulfide catalysts.

Self-Limiting Growth of Two-Dimensional Palladium between Graphene Oxide Layers.

The ability of different materials to display self-limiting growth has recently attracted an enormous amount of attention because of the importance of nanoscale materials in applications for catalysis, energy conversion, (opto)electronics, and so forth. Here, we show that the electrochemical deposition of palladium (Pd) between graphene oxide (GO) sheets result in the self-limiting growth of 5-nm-thick Pd nanosheets. The self-limiting growth is found to be a consequence of the strong interaction of Pd with the confining GO sheets, which results in the bulk growth of Pd being energetically unfavorable for larger thicknesses. Furthermore, we have successfully carried out liquid exfoliation of the resulting Pd-GO laminates to isolate Pd nanosheets and have demonstrated their high efficiency in continuous flow catalysis and electrocatalysis.

Palladium-Ceria Nanocatalyst for Hydrogen Oxidation in Alkaline Media: Optimization of the Pd-CeO2 Interface

The development of Pt-free catalyst for anion exchange membrane fuel cells is limited by the sluggish hydrogen oxidation reaction (HOR) at the anode. Previously, the use of CeO2 as a catalyst promoter facilitated drastic ennoblement of Pd for the HOR kinetics in base media. the use of CeO2 in Pd-based electrocatalysts on the anode of H2-AEMFC has led to a 5-fold improvement of power density compared to the undoped Pd/C (1). A maximum power density of 1 W cm-2 was recently demonstrated using Pd-CeO2/C catalyst, with 85% reduction of anode catalyst loading (2). The catalytic promotion of the HOR kinetics of the Pd-CeO2/C composite was ascribed to the OH- donor effect of CeO2 (1). Furthermore, CeO2 could stabilize the surface PdO species (3), which has been shown to promote the HOR kinetics on Pd (4). Although the positive catalytic effect of ceria on the electrocatalytic activity of the metal-ceria composite has clear experimental evidence, the knowledge about the optimal Pd-ceria interface is still lacking. In the present work, Pd-CeO2/C composite electrocatalysts are synthesized using three different synthetic approaches based on the flame-based reactive spray deposition technology (RSDT) as a flexible technique enabling the regulation of the particle sizes and providing more instruments to optimize the Pd-CeO2 interface. The correlation between the Pd-CeO2 interaction and the HOR activity is established through comparisons of three types of Pd-CeO2/C synthesized catalysts using electrochemical techniques and X-ray photoelectron spectroscopy (XPS). The distribution of Pd, Ce and carbon species in all the three types of catalysts is illustrated using scanning transmission electron microscopy (STEM) and elemental mapping (Figure 1). Comparing to previous works on Pd-CeO2/C catalysts (1, 5), the RSDT process improves the mixing and interface between Pd and Ce with all three types of catalysts. Particularly, the Type 1 catalyst shows the most homogeneous contact between Pd and Ce. The Pd-CeO2 chemical interaction results in partial charge transfer from metallic Pd atoms to CeO2 particles and thus, higher concentration of Pd (II) suggests stronger interaction of Pd and CeO2 (1). Based on XPS results, the Type 1 catalyst shows the highest Pd (II)/Pd (0) of 82/18 compared to the Type 2 (59/41) and Type 3 (47/53), which is in line with STEM observations (Figure 1). The HOR activity for RSDT-derived catalysts follows the trend of Type 1 > Type 2 > Type 3. This trend corroborates well with the degree of Pd oxidation state (Pd (II)/Pd (0) ratio) and Pd-CeO2 interaction. The specific activity of Type 1 catalyst surpasses the reported activity achieved by wet-chemistry based method. The RSDT technique has shown its feasibility for the development of Pd-CeO2/C composite HOR catalysts. Further implementation of the RSDT process for the optimization of Pd-CeO2/C catalyst design should concentrate on obtaining homogeneous composites with the lowest particle sizes, intimate contact between ceria and Pd, and the optimal Pd-to-Ce ratio. Application of these optimized HOR catalysts in AEMFC testing is the subject of ongoing work in our laboratories. Figure 1. HAADF images and elemental mapping of three types of Pd-CeO2/C catalysts using XEDS. The elemental maps correspond to the square region in the HAADF images. Figure 2. Mass-normalized exchange current densities for three types of RSDT-derived Pd-CeO2/C catalysts compared with the state-of-the-art Pd-CeO2/C electrocatalyst. (1) References H. A. Miller, A. Lavacchi, F. Vizza, M. Marelli, F. Di Benedetto, F. D'Acapito, Y. Paska, M. Page and D. R. Dekel, Angew.Chem.Int.Ed., 55, 20 (2016).T. J. Omasta, X. Peng, H. A. Miller, F. Vizza, L. Wang, J. R. Varcoe, D. R. Dekel and W. E. Mustain, Journal of The Electrochemical Society., 165, 15 (2018).S. Gil, M. Garcia-Vargas, F. L. Liotta, G. Pantaleo, M. Ousmane, L. Retailleau and A. Giroir-Fendler, Catalysts., 5, 2 (2015).P. L. Cabot, E. Guezala, J. C. Calpe, M. T. García and J. Casado, Journal of The Electrochemical Society., 147, 1 (2000).H. A. Miller, F. Vizza, M. Marelli, A. Zadick, L. Dubau, M. Chatenet, S. Geiger, S. Cherevko, H. Doan, R. K. Pavlicek, S. Mukerjee and D. R. Dekel, Nano Energy., 33 (2017). Figure 1

Structures, metallophilic interactions and electronic excitation energy of linear metal chain complexes PdmPtn[PH2(CH2PH)m+n-2CH2PH2]3, a theoretical investigation

The structures, metallophilic interactions and electronic excitation energy of linear metal chain complexes PdmPtn[PH2(CH2PH)m+n-2CH2PH2]3 (m + n = 2–5) (1–18) have been investigated by using MP2 and density functional theory (DFT) methods. Calculated results indicated that geometries of PdmPtn(PH2CH2PH2)3 (m + n = 2) (1–3) optimized by SVWN5 method are well consistent with those by MP2 method and experiment. Then, SVWN5 functional was used to the investigation of the large system of PdmPtn[PH2(CH2PH)m+n-2CH2PH2]3 complexes. The lowest energy structures of complexes 1–18 optimized by SVWN5 method are singlet. The lengths of Pd∙∙∙Pd and Pt∙∙∙Pt of Pdm[PH2(CH2PH)m-2CH2PH2]3 (m > 2) and Ptn[PH2(CH2PH)n-2CH2PH2]3 (n > 2) complexes at SVWN5 level are shorter than those of Pd2(PH2CH2PH2)3 and Pt2(PH2CH2PH2)3, indicating the interactions of Pd∙∙∙Pd and Pt∙∙∙Pt increase with the increase of the size of Pdm[PH2(CH2PH)m-2CH2PH2]3 and Ptn[PH2(CH2PH)n-2CH2PH2]3 complexes. Pd atoms in the mixed PdmPtn[PH2(CH2PH)m+n-2CH2PH2]3 complexes are favorable to locate at the ends of the metal chain. The lengths of Pd∙∙∙Pd and Pt∙∙∙Pt bonds in the mixed metal chain of PdmPtn[PH2(CH2PH)m+n-2CH2PH2]3 complexes have no significantly variation compared with those of the Pdm+n[PH2(CH2PH)m+n-2CH2PH2]3 and Ptm+n[PH2(CH2PH)m+n-2CH2PH2]3. But, the distances of Pd∙∙∙Pt of the mixed metal chain of PdmPtn[PH2(CH2PH)m+n-2CH2PH2]3 (m + n > 2) complexes are shorter than those of PdPt(PH2CH2PH2)3, showing the interaction between Pd and Pt increases as the increase of m + n. The WBIs of Pd∙∙∙Pd, Pd∙∙∙Pt and Pt∙∙∙Pt of complexes 1–18 are in the range of 0.22–0.25, 0.27–0.29 and 0.31–0.35, respectively, thus, there are weak interactions between adjacent transition metals in complexes 1–18. QTAIM analysis indicates that the interactions of Pd∙∙∙Pd, Pd∙∙∙Pt and Pt∙∙∙Pt of complexes 1–18 are not covalent, ionic or charge-shift bond. The gradient isosurfaces of complexes 1–18 show that the interaction between the adjacent transition metals is metallophilic interactions. The first electronic excitation energy of complexes 1–18 associated with HOMO → LUMO transition nonlinearly increases with m+n. In addition, the first electronic excitation energies of PdmPtn[PH2(CH2PH)m+n-2CH2PH2]3 complexes follow the order of Pdm+n[PH2(CH2PH)m+n-2CH2PH2]3 < PdmPtn[PH2(CH2PH)m+n-2CH2PH2]3 < Ptm+n[PH2(CH2PH) m+n-2CH2PH2]3.

An amorphous nanoporous PdCuNi-S hybrid electrocatalyst for highly efficient hydrogen production

A novel amorphous nanoporous PdCuNi-S electrocatalyst is synthesized by a two-step dealloying method. The as-formed nanoporous PdCuNi-S catalyst exhibits excellent catalytic activity for the hydrogen evolution reaction (HER) in acidic media, which is very close to commercial Pt/C catalyst. The overpotential at 10 mA cm−2 and Tafel slope are 48 mV and 35 mV dec−1, respectively. In addition, the catalyst shows good electrochemical stability in HER. The outstanding property of PdCuNi-S catalyst for hydrogen generation is attributed to the bicontinuous nanoporous structure, improved charge transfer, more bridging S22- and/or apical S2- in amorphous state and synergetic interactions of Pd, Cu, Ni and S.

Different Triple-Negative Breast Cancer Tumor Cell Lysates (TCLs) Induce Discrepant Anti-Tumor Immunity by PD1/PDL-1 Interaction.

BackgroundTCL-based immunotherapy has been applied in the field cancer therapy. However, it is un clear whether this therapy can be used to treat triple-negative breast cancer (TNBC), and different TNBC cells have distinct responses to this therapy.Material/MethodsIn the present work, we conducted 2 different TCL-based immunotherapies to treat TNBC and compared their anti-tumor effect on 4 TNBC cell lines: MDA-MB-231, MDA-MB-436, HCC1937, and HCC1187.ResultsPeripheral blood mononuclear cells (PBMC) activated by TCL and peripheral blood lymphocytes (PBL) stimulated with TCL-loaded DC demonstrated the ability to kill TNBC cells in vitro, but the killing efficiency of PBL was much higher than that of PBMC. In vivo, PBL stimulated with TCL-loaded DC can also stop the growth of TNBC tumors in mice. HCC1187 and MDA-MD-231 best respond to TCL-based immunotherapy both in vitro and in vivo. The response of HCC1937 was weaker, and that of MDA-MB-436 was lowest among the 4 cell lines. Total mRNA microarray analysis of TNBC cells showed that PDL-1 mRNA expression in HCC1937 and MDA-MD-436 cells was higher than in the other 2 TNBC cell lines, and that of MDA-MB-436 was higher than that of HCC1937. PD1 blocking can decrease the apoptosis rate. These results show that different contents of PDL-1 in TCL, by interacting with PD expression on lymphocytes, can induce different ratios of lymphocyte apoptosis, and then result in distinct response of the 4 TNBC cell lines to TCL-based immunotherapy.ConclusionsTCL-based immunotherapy has discrepant anti-tumor efficiency in different TNBC cell lines by PDL-1/PD interaction, providing the theoretical basis of TCL-based immunotherapy in TNBC.

Organocopper cross-coupling reaction for C-C bond formation on highly sterically hindered structures.

We describe a powerful, broadly applicable cross-coupling protocol that enables carbon-carbon bond formation at highly sterically hindered carbon centers (both sp2 and sp3) by employing organocopper reagents under palladium catalysis. Experimental studies and theoretical calculations indicated that the key to the unique reactivity of copper is the relatively low activation energy of the compact transmetalation transition state, due to Cu(i)-Pd(ii) interaction, which is associated with small values of deformation energy of the reactants. This reaction is applicable to a variety of bulky substrates, including compounds inert to previous cross-coupling chemistry and has high functional group tolerance.