Physico-chemical and thermal characterisation of new Co(II) complexes with pyrazole derivatives

Four new complexes having general formula [CoL₂(acr)₂] (L: 1H-pyrazole (Hpz) (1); 3-methyl-1H-pyrazole (3-Me-Hpz) (2); 4-methyl-1H-pyrazole (4-Me-Hpz) (3); 3,5-dimethyl-1H-pyrazole (Hdmpz) (4); acr: acrylato ion) were synthesised and characterised. The infrared and UV–vis spectral data indicate that these pyrazole derivatives act as unidentate while acrylato ions act as bidentate chelate ligands generating Co(II) complexes with octahedral stereochemistry. TG experiments revealed the nature of complex species as anhydrous and confirmed those compositions. The biological assays revealed a good activity against Bacillus subtilis for all complexes.     

THE CONDENSED PHOSPHATES AS INHIBITORS OF THE ZINC-ENZYME CARBONIC ANHYDRASE II

The mobilization of the zinc ion from the zinc enzyme BCA II by the condensed phosphates pyrophosphate (PP), tripolyphosphate (TPP), and higher polyphosphate (HPP) induces the inhibition of the enzymatic activity. The chelating capacity increases with the ligand concentration and with the length of the polyphosphatic chain. The activity is restored when the polyphosphate is hydrolyzed, becoming incapable of chelating the zinc ion, which is able to reform the zinc enzyme.     

Ground level ozone (O3) associated with radon (222Rn) and particulate matter (PM) concentrations in Bucharest metropolitan area and adverse health effects

The aim of this paper is to contribute with new information in the application of ground based radon (²²²Rn) observations to atmospheric research, namely its relation with air pollution due to ground-level ozone (O₃) and particle matter in two size fractions (PM10 and PM2.5) for Bucharest metropolitan area in Romania. During January 1–December 31, 2011, ground levels of radon, ozone and particulate matter (PM) have been continuously monitored in synergy with the main meteorological parameters (air temperature, humidity and pressure), and daily global air quality indices. A systematic analysis of surface ozone observations of ground level radon, ozone and PM is presented. Observational results indicate the following yearly daily mean ground level concentrations: 40.26 ± 7.54 Bq/m³ for radon, 90.51 μg/m³ for ozone, 35.96 μg/m³ for PM2.5, and 40.91 μg/m³ for PM10. The assessment of the results showed the influence of local and meteorological conditions on the daily mean radon, ozone and PM concentrations. However, in densely populated metropolitan area of Bucharest the mean daily values of ozone, PM2.5, PM10, and attached ²²²Rn are sometimes higher than European Community limit values leading to serious public concern during the last years. Due to the high risk of increased levels of O₃, PM2.5, PM10, and attached ²²²Rn on human health respiratory function (especially for children and older persons), and urban green, the results are very useful for atmospheric, radiological protection, epidemiological and environmental studies.     

Synthesis,physico-chemical characterization and thermal behavior of new complexes with N4O2 donor set

Three new coordinative compounds of the type [Co(en)₂CO₃]·0.75H₂O (1) and [M(en)₂(H₂O)₂]CO₃ ((2) M:Ni, (3) M:Cu; en: ethylenediamine) were synthesized and characterized. The IR and UV–Vis spectral data indicate that ethylenediamine acts as chelate, while carbonate ions act as bidentate chelate ligand for (1)/counter ion for (2) and (3) generating complexes with octahedral stereochemistry. The thermal behavior provided confirmation of the complexes composition, as well as the number and the nature of water molecules and the intervals of thermal stability. The biological assays revealed a good activity against Enterococcus faecium for copper complex.     

Toward a rational design of poly(2,7-carbazole) derivatives for solar cells

On the basis of theoretical models and calculations, several alternating polymeric structures have been investigated to develop optimized poly(2,7-carbazole) derivatives for solar cell applications. Selected low band gap alternating copolymers have been obtained via a Suzuki coupling reaction. A good correlation between DFT theoretical calculations performed on model compounds and the experimental HOMO, LUMO, and band gap energies of the corresponding polymers has been obtained. This study reveals that the alternating copolymer HOMO energy level is mainly fixed by the carbazole moiety, whereas the LUMO energy level is mainly related to the nature of the electron-withdrawing comonomer. However, solar cell performances are not solely driven by the energy levels of the materials. Clearly, the molecular weight and the overall organization of the polymers are other important key parameters to consider when developing new polymers for solar cells. Preliminary measurements have revealed hole mobilities of about 1 x 10(-3) cm2 x V(-1) x s(-1) and a power conversion efficiency (PCE) up to 3.6%. Further improvements are anticipated through a rational design of new symmetric low band gap poly(2,7-carbazole) derivatives.     

Cyanido-bridged Fe(III)-Mn(III) heterobimetallic materials built from Mn(III) Schiff base complexes and di- or tri-cyanido Fe(III) precursors

The reaction of [Fe(III)L(CN)(3)](-) (L being bpca = bis(2-pyridylcarbonyl)amidate, pcq = 8-(pyridine-2-carboxamido)quinoline) or [Fe(III)(bpb)(CN)(2)](-) (bpb = 1,2-bis(pyridine-2-carboxamido)benzenate) ferric complexes with Mn(III) salen type complexes afforded seven new bimetallic cyanido-bridged Mn(III)-Fe(III) systems: [Fe(pcq)(CN)(3)Mn(saltmen)(CH(3)OH)]·CH(3)OH (1), [Fe(bpca)(CN)(3)Mn(3-MeO-salen)(OH(2))]·CH(3)OH·H(2)O (2), [Fe(bpca)(CN)(3)Mn(salpen)] (3), [Fe(bpca)(CN)(3)Mn(saltmen)] (4), [Fe(bpca)(CN)(3)Mn(5-Me-saltmen)]·2CHCl(3) (5), [Fe(pcq)(CN)(3)Mn(5-Me-saltmen)]·2CH(3)OH·0.75H(2)O (6), and [Fe(bpb)(CN)(2)Mn(saltmen)]·2CH(3)OH (7) (with saltmen(2-) = N,N'-(1,1,2,2-tetramethylethylene)bis(salicylideneiminato) dianion, salpen(2-) = N,N'-propylenebis(salicylideneiminato) dianion, salen(2-) = N,N'-ethylenebis(salicylideneiminato) dianion). Single crystal X-ray diffraction studies were carried out for all these compounds indicating that compounds 1 and 2 are discrete dinuclear [Fe(III)-CN-Mn(III)] complexes while systems 3-7 are heterometallic chains with {-NC-Fe(III)-CN-Mn(III)} repeating units. These chains are connected through π-π and short contact interactions to form extended supramolecular networks. Investigation of the magnetic properties revealed the occurrence of antiferromagnetic Mn(III)···Fe(III) interactions in 1-4 while ferromagnetic Mn(III)···Fe(III) interactions were detected in 5-7. The nature of these Mn(III)···Fe(III) magnetic interactions mediated by a CN bridge appeared to be dependent on the Schiff base substituent. The packing is also strongly affected by the nature of the substituent and the presence of solvent molecules, resulting in additional antiferromagnetic interdinuclear/interchain interactions. Thus the crystal packing and the supramolecular interactions induce different magnetic properties for these systems. The dinuclear complexes 1 and 2, which possess a paramagnetic S(T) = 3/2 ground state, interact antiferromagnetically in their crystal packing. At high temperature, the complexes 3-7 exhibit a one-dimensional magnetic behavior, but at low temperature their magnetic properties are modulated by the supramolecular arrangement: a three-dimensional antiferromagnetic order with a metamagnetic behavior is observed for 3, 4, and 7, and Single-Chain Magnet properties are detected for 5 and 6.     

Periodic solutions of singular radially symmetric systems with superlinear growth

We prove the existence of infinitely many periodic solutions for periodically forced radially symmetric systems of second-order ODE??s, with a singularity of repulsive type, where the nonlinearity has a superlinear growth at infinity. These solutions have periods, which are large integer multiples of the period of the forcing, and rotate exactly once around the origin in their period time, while having a fast oscillating radial component. Analogous results hold in the case of an annular potential well.     

Cooperation in dividing the cake

This paper defines models of cooperation among players partitioning a completely divisible good (such as a cake or a piece of land). The novelty of our approach lies in the players’ ability to form coalitions before the actual division of the good with the aim to maximize the average utility of the coalition. A social welfare function which takes into account coalitions drives the division. In addition, we derive a cooperative game which measures the performance of each coalition. This game is compared with the game in which players start cooperating only after the good has been portioned and has been allocated among the players. We show that a modified version of the game played before the division outperforms the game played after the division.