Chemistry - A European Journal
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Nitrogen Photofixation on Nanostructured Iron Titanate Films Abstract A nanostructured iron titanate thin film has been prepared by a sol–gel method from iron(III ) chloride and titanium tetraisopropylate. Energy‐dispersive X‐ray analysis and Mößbauer spectroscopy suggest the presence of a Fe2 Ti2 O7 phase, which was previously obtained as an intermediary phase upon heating ilmenite. In the presence of ethanol or humic acids and traces of oxygen, the novel film photocatalyzes the fixation of dinitrogen to ammonia (17 μM ) and nitrate (45 μM ). In the first observable reaction step, hydrazine is produced and then undergoes further photoreduction to ammonia. Oxidation of the latter by oxygen affords nitrate as the final product. Since the reaction occurs also in air and with visible light (λ >455 nm), and since the iron titanate phase may be formed by the weathering of ilmenite minerals, it may be a model for mutual nonenzymatic nitrogen fixation in nature.
Chemistry - A European Journal - Tập 9 Số 2 - Trang 561-565 - 2003
Efficient Solar‐Driven Nitrogen Fixation over Carbon–Tungstic‐Acid Hybrids Abstract Ammonia synthesis under mild conditions is of supreme interest. Photocatalytic nitrogen fixation with water at room temperature and atmospheric pressure is an intriguing strategy. However, the efficiency of this method has been far from satisfied for industrialization, mainly due to the sluggish cleavage of the N≡N bond. Herein, we report a carbon–tungstic‐acid (WO3 ⋅ H2 O) hybrid for the co‐optimization of N2 activation as well as subsequent photoinduced protonation. Efficient ammonia evolution reached 205 μmol g−1 h−1 over this hybrid under simulated sunlight. Nitrogen temperature‐programmed desorption revealed the decisive role of carbon in N2 adsorption. Photoactive WO3 ⋅ H2 O guaranteed the supply of electrons and protons for subsequent protonation. The universality of carbon modification for enhancing the N2 reduction was further verified over various photocatalysts, shedding light on future materials design for ideal solar energy utilization.
Chemistry - A European Journal - Tập 22 Số 39 - Trang 13819-13822 - 2016
Electric Double‐Layer Capacitors Based on Highly Graphitized Nanoporous Carbons Derived from ZIF‐67 Abstract Nanoporous carbons (NPCs) have large specific surface areas, good electrical and thermal conductivity, and both chemical and mechanical stability, which facilitate their use in energy storage device applications. In the present study, highly graphitized NPCs are synthesized by one‐step direct carbonization of cobalt‐containing zeolitic imidazolate framework‐67 (ZIF‐67). After chemical etching, the deposited Co content can be completely removed to prepare pure NPCs with high specific surface area, large pore volume, and intrinsic electrical conductivity (high content of sp 2 ‐bonded carbons). A detailed electrochemical study is performed using cyclic voltammetry and galvanostatic charge–discharge measurements. Our NPC is very promising for efficient electrodes for high‐performance supercapacitor applications. A maximum specific capacitance of 238 F g−1 is observed at a scan rate of 20 mV s−1 . This value is very high compared to previous works on carbon‐based electric double layer capacitors.
Chemistry - A European Journal - Tập 20 Số 26 - Trang 7895-7900 - 2014
Toward the Complete Prediction of the <sup>1</sup>H and <sup>13</sup>C NMR Spectra of Complex Organic Molecules by DFT Methods: Application to Natural Substances Abstract The NMR parameters (1 H and 13 C chemical shifts and coupling constants) for a series of naturally occurring molecules have been calculated mostly with DFT methods, and their spectra compared with available experimental ones. The comparison includes strychnine as a test case, as well as some examples of recently isolated natural products (corianlactone, daphnipaxinin, boletunone B) featuring unusual and/or crowded structures and, in the case of boletunone B, being the subject of a recent revision. Whenever experimental spectra were obtained in polar solvents, the calculation of NMR parameters was also carried out with the Integral Equation‐Formalism Polarizable Continuum Model (IEF‐PCM) continuum method. The computed results generally show a good agreement with experiment, as judged not only by statistical parameters but also by visual comparison of line spectra. The origin of the remaining discrepancies is attributed to the incomplete modeling of conformational and specific solvent effects.
Chemistry - A European Journal - Tập 12 Số 21 - Trang 5514-5525 - 2006
Porphyrin/Platinum(II) C^N^N Acetylide Complexes: Synthesis, Photophysical Properties, and Singlet Oxygen Generation Abstract A new class of substituted porphyrins has been developed in which a different number of cyclometalated PtII C^N^N acetylides and polyethylene glycol (PEG) chains are attached to the meso positions of the porphyrin core, which are meant for photophysical, electrochemical, and in vitro light‐induced singlet oxygen (1 O2 ) generation studies. All of these ZnII porphyrin–PtII C^N^N acetylide conjugates show moderate to high (Φ Δ II C^N^N antenna units to the ZnII porphyrin core, which shows sensitized luminescence, as shown by quenching of PtII C^N^N‐based luminescence. Electrochemical measurements show a set of redox processes that are approximately the sum of what is observed for the PtII C^N^N acetylide and ZnII porphyrin units. UV/Vis spectroscopic properties are supported by DFT calculations.
Chemistry - A European Journal - Tập 22 Số 12 - Trang 4164-4174 - 2016
Structure‐Based Design of Platinum(II) Complexes as c‐<i>myc</i> Oncogene Down‐Regulators and Luminescent Probes for G‐Quadruplex DNA Abstract A series of platinum(II) complexes with tridentate ligands was synthesized and their interactions with G‐quadruplex DNA within the c‐myc gene promoter were evaluated. Complex 1 , which has a flat planar 2,6‐bis(benzimidazol‐2‐yl)pyridine (bzimpy) scaffold, was found to stabilize the c‐myc G‐quadruplex structure in a cell‐free system. An in silico G‐quadruplex DNA model has been constructed for structure‐based virtual screening to develop new PtII ‐based complexes with superior inhibitory activities. By using complex 1 as the initial structure for hit‐to‐lead optimization, bzimpy and related 2,6‐bis(pyrazol‐3‐yl)pyridine (dPzPy) scaffolds containing amine side‐chains emerge as the top candidates. Six of the top‐scoring complexes were synthesized and their interactions with c‐myc G‐quadruplex DNA have been investigated. The results revealed that all of the complexes have the ability to stabilize the c‐myc G‐quadruplex. Complex 3 a ([PtII L2R ]+ L2 =2,6‐bis[1‐(3‐piperidinepropyl)‐1H ‐enzo[d ]imidazol‐2‐yl]pyridine, R =Cl) displayed the strongest inhibition in a cell‐free system (IC50 =2.2 μM ) and was 3.3‐fold more potent than that of 1 . Complexes 3 a and 4 a ([PtII L3R ]+ ; L3 =2,6‐bis[1‐(3‐morpholinopropyl)‐1H ‐pyrazol‐3‐yl]pyridine, R =Cl) were found to effectively inhibit c‐myc gene expression in human hepatocarcinoma cells with IC50 values of ≈17 μM , whereas initial hit 1 displayed no significant effect on gene expression at concentrations up to 50 μM . Complexes 3 a and 4 a have a strong preference for G‐quadruplex DNA over duplex DNA, as revealed by competition dialysis experiments and absorption titration; 3 a and 4 a bind G‐quadruplex DNA with binding constants (K ) of approximately 106 –107 dm3 mol−1 , which are at least an order of magnitude higher than the K values for duplex DNA. NMR spectroscopic titration experiments and molecular modeling showed that 4 a binds c‐myc G‐quadruplex DNA through an external end‐stacking mode at the 3′‐terminal face of the G‐quadruplex. Intriguingly, binding of c‐myc G‐quadruplex DNA by 3 b is accompanied by an increase of up to 38‐fold in photoluminescence intensity at λ max =622 nm.
Chemistry - A European Journal - Tập 16 Số 23 - Trang 6900-6911 - 2010
The Important Role of the Nuclearity, Rigidity, and Solubility of Phosphane Ligands in the Biological Activity of Gold(I) Complexes Abstract A series of 4‐ethynylaniline gold(I) complexes containing monophosphane (1,3,5‐triaza‐7‐phosphaadamantane (pta; 2 ), 3,7‐diacetyl‐1,3,7‐triaza‐5‐phosphabicyclo[3.3.1]nonane (3 ), and PR3 , with R=naphthyl (4 ), phenyl (5 ), and ethyl (6 )) and diphosphane (bis(diphenylphosphino)acetylene (dppa; 7 ), trans ‐1,2‐bis(diphenylphosphino)ethene (dppet; 8 ), 1,2‐bis(diphenylphosphino)ethane (dppe; 9 ), and 1,3‐bis(diphenylphosphino)propane (dppp; 10 )) ligands have been synthesized and their efficiency against tumor cells evaluated. The cytotoxicity of complexes 2 –10 was evaluated in human colorectal (HCT116) and ovarian (A2780) carcinoma as well as in normal human fibroblasts. All the complexes showed a higher antiproliferative effect in A2780 cells, with the cytotoxicity decreasing in the following order 5 >6 =9 =10 >8 >2 >4 >7 >3 . Complex 4 stands out for its very high selectivity towards ovarian carcinoma cells (IC50 =2.3 μm ) compared with colorectal carcinoma and normal human fibroblasts (IC50 >100 μm ), which makes this complex very attractive for ovarian cancer therapy. Its cytotoxicity in these cells correlates with the induction of the apoptotic process and an increase of intracellular reactive oxygen species (ROS). The effects of the nuclearity, rigidity, and solubility of these complexes on their biological activity were also analyzed. X‐ray crystal structure determination allowed the identification of short N−H⋅⋅⋅π contacts as the main driving forces for the three‐dimensional packing in these molecules.
Chemistry - A European Journal - Tập 24 Số 55 - Trang 14654-14667 - 2018
Polyelectrolyte‐Induced Self‐Assembly of Positively Charged Alkynylplatinum(II)–Terpyridyl Complexes in Aqueous Media Abstract Polyelectrolytes carrying multiple negative charges were found to induce the aggregation and self‐assembly of the positively charged platinum(II)–terpyridyl complexes in aqueous media. The aggregation and self‐assembly of the complexes were driven by electrostatic interactions between the polymer and the complex, and by terpyridine ligand π–π stacking and platinum–platinum (metal–metal) interactions. As a result, remarkable UV/Vis and emission spectral changes were observed. The spectroscopic property changes were related to the structural properties of the metal complexes as well as the polyelectrolytes. The induced self‐assembly of the platinum complexes was also strongly affected by the solution properties of the aqueous media, for example, the solution pH, ionic strength, and the percentage of organic solvent added.
Chemistry - A European Journal - Tập 14 Số 15 - Trang 4577-4584 - 2008
NIR‐Emissive Alkynylplatinum(II) Terpyridyl Complex as a Turn‐On Selective Probe for Heparin Quantification by Induced Helical Self‐Assembly Behaviour
Chemistry - A European Journal - Tập 17 Số 43 - Trang 11987-11990 - 2011
Functionalized Fe<sub>3</sub>O<sub>4</sub> Nanoparticles for Detecting Zinc Ions in Living Cells and Their Cytotoxicity
Chemistry - A European Journal - Tập 18 Số 19 - Trang 5843-5847 - 2012
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