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排序方式: 共有670条查询结果,搜索用时 15 毫秒
31.
Dr. Martin Piesch Dr. Amélie Nicolay Dr. Maria Haimerl Dr. Michael Seidl Dr. Gábor Balázs Prof. T. Don Tilley Prof. Dr. Manfred Scheer 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(45):e202201144
The bridging MeCN ligand in the dicopper(I) complexes [(DPFN)Cu2(μ,η1 : η1-MeCN)][X]2 (X=weakly coordinating anion, NTf2 ( 1 a ), FAl[OC6F10(C6F5)]3 ( 1 b ), Al[OC(CF3)3]4 ( 1 c )) was replaced by white phosphorus (P4) or yellow arsenic (As4) to yield [(DPFN)Cu2(μ,η2 : η2-E4)][X]2 (E=P ( 2 a – c ), As ( 3 a – c )). The molecular structures in the solid state reveal novel coordination modes for E4 tetrahedra bonded to coinage metal ions. Experimental data and quantum chemical computations provide information concerning perturbations to the bonding in coordinated E4 tetrahedra. Reactions with N-heterocyclic carbenes (NHCs) led to replacement of the E4 tetrahedra with release of P4 or As4 and formation of [(DPFN)Cu2(μ,η1 : η1-MeNHC)][X]2 ( 4 a,b ) or to an opening of one E−E bond leading to an unusual E4 butterfly structural motif in [(DPFN)Cu2(μ,η1 : η1-E4DippNHC)][X]2 (E=P ( 5 a,b ), E=As ( 6 )). With a cyclic alkyl amino carbene (EtCAAC), cleavage of two As−As bonds was observed to give two isomers of [(DPFN)Cu2(μ,η2 : η2-As4EtCAAC)][X]2 ( 7 a,b ) with an unusual As4-triangle+1 unit. 相似文献
32.
E. Marin F. Boschetto M. Zanocco W. Zhu T. Adachi N. Kanamura T. Yamamoto B.J. McEntire E.N. Jones C. Powell J. Hendry R.M. Bock B.S. Bal G. Pezzotti 《Materials Today Chemistry》2021
Most structural bioceramics are comprised of metallic oxides such as alumina and zirconia. They are generally considered to be completely bioinert, but a non-oxide ceramic, silicon nitride, achieves equivalent levels of mechanical reliability while being bioactive. Silicon nitride can not only stimulate cellular proliferation but it is also antipathogenic with demonstrated efficacy against Gram-positive and Gram-negative bacteria, fungi, and viruses. In this work, three physical vapor deposition coatings with different Si:N ratios (silicon-rich, stoichiometric, and nitrogen-rich) were deposited on mirror-polished silica glass substrates. The coatings were characterized by spectroscopic and microscopic techniques and tested in vitro against E. coli and KUSA-A1 mesenchymal cells. Results showed that nitrogen-enriched SixNy has a strong antibacterial effect against E. coli and contributes to cellular proliferation while silicon-enriched SixNy stimulates the production of bone tissue, with higher indexes for mineralization and quality. These results suggest that SixNy's biological properties can be optimized for specific applications by carefully tuning its surface chemistry. 相似文献
33.
Dr. Julian Heinrich Dr. Karolina Bossak-Ahmad Mie Riisom Dr. Haleh H. Haeri Tasha R. Steel Vinja Hergl Alexander Langhans Corinna Schattschneider Jannis Barrera Dr. Stephen M. F. Jamieson Prof. Matthias Stein Prof. Dariush Hinderberger Prof. Christian G. Hartinger Prof. Wojciech Bal Prof. Nora Kulak 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(72):18093-18102
Redox-active Cu(II) complexes are able to form reactive oxygen species (ROS) in the presence of oxygen and reducing agents. Recently, Faller et al. reported that ROS generation by Cu(II) ATCUN complexes is not as high as assumed for decades. High complex stability results in silencing of the Cu(II)/Cu(I) redox cycle and therefore leads to low ROS generation. In this work, we demonstrate that an exchange of the α-amino acid Gly with the β-amino acid β-Ala at position 2 (Gly2→β-Ala2) of the ATCUN motif reinstates ROS production (•OH and H2O2). Potentiometry, cyclic voltammetry, EPR spectroscopy and DFT simulations were utilized to explain the increased ROS generation of these β-Ala2-containing ATCUN complexes. We also observed enhanced oxidative cleavage activity towards plasmid DNA for β-Ala2 compared to the Gly2 complexes. Modifications with positively charged Lys residues increased the DNA affinity through electrostatic interactions as determined by UV/VIS, fluorescence, and CD spectroscopy, and consequently led to a further increase in nuclease activity. A similar trend was observed regarding the cytotoxic activity of the complexes against several human cancer cell lines where β-Ala2 peptide complexes had lower IC50 values compared to Gly2. The higher cytotoxicity could be attributed to an increased cellular uptake as determined by ICP-MS measurements. 相似文献
34.
Bal Sydulu Singu Umashankar Male Palaniappan Srinivasan Srinivas Pabba 《Journal of Solid State Electrochemistry》2014,18(7):1995-2003
Polyaniline sulphate salt titanium dioxide composite (PANI-H2SO4·TiO2) was synthesized by chemical in situ polymerization of aniline in the presence of TiO2. The effect of anionic surfactant (sodium lauryl sulphate) in this reaction was also assessed. During the polymerization reaction, sodium lauryl sulphate (SLS) is converted to dodecyl hydrogen sulphate (DHS) in the presence of acidic medium and gets doped onto polyaniline along with sulphuric acid dopant, i.e. formation of polyaniline-sulphate-dodecyl hydrogen sulphate-titanium dioxide composite (PANI-H2SO4-DHS·TiO2). In the PANI-H2SO4-DHS·TiO2 composite, the presence of DHS is confirmed by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and energy-dispersive X-ray analysis (EDAX) and TiO2 is confirmed by XRD and EDAX results. In PANI-H2SO4-DHS·TiO2 system, the nanoparticle of TiO2 (10–20 nm) is uniformly embedded on nanofibres (20–60 nm) of PANI-H2SO4-DHS, and some part of PANI-H2SO4-DHS·TiO2 forms core–shell morphology, wherein TiO2 is in core and PANI-H2SO4-DHS in shell forms. Stability of PANI-H2SO4-DHS increases due to the incorporation of stable TiO2. Utility of PANI-TiO2 composite was carried out in supercapacitor cell system by performing cyclic voltammetry, galvanostatic charge–discharge and electrochemical impedance spectroscopic techniques in 1 M H2SO4 solution. Very low values of solution resistance, charge transfer resistance and time constant are obtained between 0.2 and 0.6 V. Initial specific capacitance values for the cell carried out at low and high current densities are found to be 280 and 205 F g?1, respectively, and after 1,700 charge–discharge cycles, its retention in the specific capacitance values is found to be the same (65–66 %) with coulombic efficiency of 98–100 %. A capacitor can work even at a high discharge rate. The efficiency of oxidizing and doping power increases with the use of a surfactant. Moreover, the use of a long chain surfactant dopant containing polyaniline as an electrode material plays an important role to increase the performance of the supercapacitor by allowing the electrolyte to easily enter and come out from PANI electrodes. 相似文献
35.
Eric Mädl Dr. Mikhail V. Butovskii Dr. Gábor Balázs Dr. Eugenia V. Peresypkina Dr. Alexander V. Virovets Michael Seidl Prof. Dr. Manfred Scheer 《Angewandte Chemie (International ed. in English)》2014,53(29):7643-7646
Unprecedented functionalized products with an η4‐P5 ring are obtained by the reaction of [Cp*Fe(η5‐P5)] ( 1 ; Cp*=η5‐C5Me5) with different nucleophiles. With LiCH2SiMe3 and LiNMe2, the monoanionic products [Cp*Fe(η4‐P5CH2SiMe3)]? and [Cp*Fe(η4‐P5NMe2)]?, respectively, are formed. The reaction of 1 with NaNH2 leads to the formation of the trianionic compound [{Cp*Fe(η4‐P5)}2N]3?, whereas the reaction with LiPH2 yields [Cp*Fe(η4‐P5PH2)]? as the main product, with {[Cp*Fe(η4‐P5)]2PH}2? as a byproduct. The calculated energy profile of the reactions provides a rationale for the formation of the different products. 相似文献
36.
37.
B. Ch. Kholkhoev A. S. Buinov S. A. Bal’zhinov I. A. Farion V. G. Makotchenko V. E. Fedorov M. N. Kozlova P. S. Timashev V. F. Burdukovskii R. K. Chailakhyan 《Polymer Science Series A》2017,59(2):223-227
Highly concentrated dispersions of polyvinylpyrrolidone-stabilized graphene were prepared. Using transmission electron microscopy, it was found that the graphene particles consisted, on average, of one to four layers, with the lateral size of 50–400 nm. From these dispersions, new film composites of chitosan with the filler content up to 4 wt % characteristic of electrical conductivity as high as 1.9 × 10–2 S/cm were formed. 相似文献
38.
Török B Szöllösi G Balázsik K Felföldi K Kun I Bartók M 《Ultrasonics sonochemistry》1999,6(1-2):97-103
Sonochemical chemo- and enantioselective hydrogenations over supported platinum catalysts are described. We disclose our results with respect to a sonochemical modification of the chemoselective hydrogenation of cinnamaldehyde over supported platinum catalysts, and the asymmetric hydrogenation of ethyl pyruvate promoted by various ultrasonic pretreatments. The ultrasonic pretreatment of the supported platinum catalysts was found to be highly beneficial in almost every case, improving both the catalytic activity and selectivity. The effect of additional experimental variables, such as hydrogen pressure, catalyst support, temperature and the ultrasonic insonation time were also studied. The enantioselectivity of the hydrogenation of ethyl pyruvate increased up to 97.1% ee. In the case of cinnamaldehyde hydrogenation, the selective preparation of cinnamyl alcohol became possible. The theoretical aspects of the working mechanisms in comparison with 'silent' reactions will also be provided. 相似文献
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