Triethylammonium bis(tetrafluoromethylsulfonyl)amide protic ionic liquid as an electrolyte for electrical double-layer capacitors

This study describes the preparation, characterization and application of [Et(3)NH][TFSA], either neat or mixed with acetonitrile, as an electrolyte for supercapacitors. Thermal and transport properties were evaluated for the neat [Et(3)NH][TFSA], and the temperature dependence of viscosity and conductivity can be described by the VTF equation. The evolution of conductivity with the addition of acetonitrile rendered it possible to determine the optimal mixture at 25 °C, with a weight fraction of acetonitrile of 0.5. This mixture was also evaluated for transport properties, and showed a Newtonian behavior, as the neat PIL. An electrochemical study demonstrated, at first, a passivation on Al after the second cyclic voltammogram. Subsequently, the electrochemical window was estimated using a three-electrode cell to 4 V on a platinum electrode, and to 2.5 V on activated carbon. Finally, the neat PIL was found to exhibit good performances as promising electrolyte for supercapacitor applications.     

Bioactive papaverine derivatives bind G-quadruplexes selectively

G-quadruplexes are a family of DNA secondary structures resulting from the folding of a guanine-rich sequence. Targeting quadruplexes by small molecules is an approach that is currently being studied with the aim of exploring their biological roles and developing new anti-cancer agents. There is evidence that the formation of G4 structures by telomeric DNA can be used to inhibit the enzyme activity of telomerase, and thereby to activate the pathway to senescence in tumour cells. It was previously shown that the papaverine oxidation products 6a,12a-diazadibenzo-[a,g]fluorenylium derivative (ligand I) and 2,3,9,10-tetramethoxy-12-oxo-12H-indolo[2,1-a]isoquinolinium chloride (ligand II) bind to G-quadruplex representing the human telomeric sequence. These ligands possess the ability to inhibit telomerase and polymerase action at the micromolar level. Here we report a DNA binding study on these two ligands and a new derivative 2-(2-carboxy-4,5-dimethoxyphenyl0-6,7-dimethoxyisoquiloliniuminner salt (ligand III) in order to evaluate their binding selectivity to samples of nucleic acids (ssDNA, dsDNA, triplexes, and quadruplexes). Simultaneous investigations on several DNA-ligand complexes carried out using an equilibrium dialysis approach revealed pronounced binding selectivity of ligand I and ligand II to tetraplex DNA structures over the doublestranded DNA forms.     

Collapsed Cu(II)-hydroxamate metallacrowns

Degradation of a strained, thermodynamically destabilized pentanuclear copper(II) 12-metallacrown-4 complex based on a picoline hydroxamic acid resulted in the formation of the tetranuclear compounds which are the first examples of solely hydroxamate-based Cu(II) metallacrown complexes with a collapse of the metallamacrocyclic cavity.     

Palladium-coated nickel nanoclusters: new Hiyama cross-coupling catalysts

The advantages of bimetallic nanoparticles as C-C coupling catalysts are discussed, and a simple, bottom-up synthesis method of core-shell Ni-Pd clusters is presented. This method combines electrochemical and 'wet chemical' techniques, and enables the preparation of highly monodispersed structured bimetallic nanoclusters. The double-anode electrochemical cell is described in detail. The core-shell Ni-Pd clusters were then applied as catalysts in the Hiyama cross-coupling reaction between phenyltrimethoxysilane and various haloaryls. Good product yields were obtained with a variety of iodo- and bromoaryls. We found that, for a fixed amount of Pd atoms, the core-shell clusters outperform both the monometallic Pd clusters and the alloy bimetallic Ni-Pd ones. THF is an excellent solvent for this process, with less than 2% homocoupling by-product. The roles of the stabiliser and the solvent are discussed.     

Electrodeposition of poly(N-vinylcarbazole) at the three-phase junction. Formation of very different polymer structures

Poly(N-vinylcarbazole) films can be deposited at the three-phase boundary when the organic phase contains only monomer, N-vinylcarbazole, while the aqueous phase contains supporting electrolyte. A cylindrical platinum microelectrode is immersed into the two-liquid system in such a way that a part of it is located in one liquid and the other part resides in the second liquid. The thickness of the reaction layer, or the width of the microelectrode zone where the polymer grows, depends on the kind of ions present in the aqueous phase and the time of the experiment. The structure of the deposited polymer may be very different and depends on the distance from the three-phase boundary and the type of the anion present in the aqueous phase. The key parameters here are the local electrode potential and the local concentration of the anions. The list of obtained polymer structures includes, among others, arrays of perfectly arranged deep oval channels and groups of microcrystals. The porosity of the polymer deposits increases with the distance from the aqueous phase.     

Synthesis, cytotoxic effect, and structure-activity relationship of Pd(II) complexes with coumarin derivatives

We report the influence of the substituent at the N atom of the ligands on the synthesis, biological activity, and stability of Pd(II) complexes of the general formula PdL(2). The compounds adopt a cis or trans configuration with respect to the substituent at the nitrogen atom. Sterically hindered substituents promote the formation of trans isomers, whereas when the nitrogen atom is unsubstituted, cis isomers are formed. The compounds were characterized by elemental analysis, infrared and 1H NMR spectroscopies, and electrospray mass spectrometry. The complexes were also studied using X-ray diffraction and computational DFT methods. Both complexes cis-3a and trans-3c exhibit square-planar geometries around the Pd(II) atom. The cytotoxic effects of these complexes were examined on two human leukemia cell lines, HL-60 and NALM-6. Pd complex cis-3a showed significant cytotoxic activity. The effects exhibited by this complex were comparable to those reported for carboplatin. Loigand 2a was not cytotoxic. Computational analysis carried out at the PB/B3LYP/LACVP**//mPW1PW91/LanL2DZ level showed excellent correlation between the energy difference of the cis and trans isomers and the cytotoxic activity, rendering computations a useful predictive tool for the design of new drugs.     

Fluorescence anisotropy and FRET studies of G-quadruplex formation in presence of different cations

Results of the steady-state fluorescence, anisotropy and FRET measurements of G-quadruplex formation in the presence of selected cations (Li(+), Na(+), K(+), NEt(4)(+) and Mg(2+)) are reported. Three different fluorescent oligonucleotides with human telomeric sequence labeled with fluorescein (FAM) and tetramethylrhodamine (TAMRA) were investigated: a dual-labeled 21-mer denoted as PSO (Potassium Sensing Oligonucleotide) and two 5'- and 3'- single-labeled probes, FAM-21 and 21-TAMRA, respectively. The fluorescence signal of FAM-21 increased significantly for all systems and the fluorescence enhancement was comparable in magnitude for monovalent cations but it was more pronounced for Mg(2+) cation. This phenomenon was attributed to the protolytic equilibria of FAM affected by the variation in ionic strength. On the other hand, fluorescence of TAMRA was enhanced selectively by Na(I) cation that was explained by the dequenching of TAMRA emission originated from the peculiarity of the basket-type structure of Na(I)-quadruplex. Anisotropy of FAM-21 (but not 21-TAMRA) appeared to be sensitive to the G-quadruplex formation, showing significant increase with an increase in cation concentration and indicating some restrictions in rotational depolarization of FAM. FRET experiments revealed that all tested cations caused quenching of FAM fluorescence in PSO, but only Na(+) and K(+) ions produced sensitized emission of TAMRA acceptor. Higher FRET efficiency observed in the presence of sodium ion was attributed to the specific spectral factor and steric interactions in the basket-type Na(I)-quadruplex.