Synthesis,structure, and magnetic properties of the cobalt(<Emphasis Type="SmallCaps">II</Emphasis>) 1,3,5-benzenetricarboxylate layered coordination polymer

The reaction of Co(NO₃)₂·6H₂O with 1,3,5-benzenetricarboxylic acid (H₃btc, trimesic acid) in DMF at 100 °C afforded the coordination polymer [Co₃(dmf)₆(btc)(Hbtc)(H₂btc)]··9H₂O (1) (dmf is N,N′-dimethylformamide, DMF). According to the X-ray diffraction study, the metal-organic coordination polymer is composed of planar honeycomb (6,3) networks, in which the organic benzenetricarboxylate anions and the inorganic Co²⁺ cations play a role of three-connected nodes. Disordered water molecules are intercalated between the layers. A study of the magnetic properties showed the presence of a weak antiferromagnetic coupling between the Co²⁺ ions (S = 3/2). Dedicated to Academician G. A. Abakumov on the occasion of his 70th birthday. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1719–1723, September, 2007.     

Arsenic Speciation Analysis in Solutions Treated with Zeolites

Experiments have been carried out to study the behaviour of organoarsenicals treated with zeolites by means of speciation analysis. IC-ICP-MS was applied to identify and quantify arsenite, arsenate and the following organoarsenicals: monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), trimethylarsine oxide (TMAO), tetramethylarsonium bromide (TMA⁺), arsenobetaine (AsB) and arsenocholine (AsC). Zeolites loaded with ferrous ions did not significantly increase the retention of inorganic arsenic species compared to the native zeolites, while there was a ten-fold removal of arsenate relating to arsenite. The formation of As(V) and DMA in the leachates containing clinoptilolites and mordenites was confirmed in the presence of natural and synthetic zeolites. Arsenobetaine and arsenocholine yielded higher levels of arsenate than the methylated species.     

Combined charge and spin density experimental study of the yttrium(III) semiquinonato complex Y(HBPz3)2(DTBSQ) and DFT calculations

High-resolution X-ray diffraction and polarized neutron diffraction experiments have been performed on the Y-semiquinonate complex, Y(HBPz3)2(DTBSQ), in order to determine the charge and spin densities in the paramagnetic ground state, S = (1/2). The aim of these combined studies is to bring new insights to the antiferromagnetic coupling mechanism between the semiquinonate radical and the rare earth ion in the isomorphous Gd(HBPz3)2(DTBSQ) complex. The experimental charge density at 106 K yields detailed information about the bonding between the Y3+ ion and the semiquinonate ligand; the topological charge of the yttrium atom indicates a transfer of about 1.5 electrons from the radical toward the Y3+ ion in the complex, in agreement with DFT calculations. The electron density deformation map reveals well-resolved oxygen lone pairs with one lobe polarized toward the yttrium atom. The determination of the induced spin density at 1.9 K under an applied magnetic field of 9.5 T permits the visualization of the delocalized magnetic orbital of the radical throughout the entire molecule. The spin is mainly distributed on the oxygen atoms [O1 (0.12(1) mu B), O2(0.11(1) mu B)] and the carbon atoms [C21 (0.24(1) mu B), C22(0.20(1) mu B), C24(0.16(1) mu B), C25(0.12(1) mu B)] of the carbonyl ring. A significant spin delocalization on the yttrium site of 0.08(2) mu B is observed, proving that a direct overlap with the radical magnetic orbital can occur at the rare earth site and lead to antiferromagnetic coupling. The DFT calculations are in good quantitative agreement with the experimental charge density results, but they underestimate the spin delocalization of the oxygen toward the yttrium and the carbon atoms of the carbonyl ring.     

Production of submicron-size monodisperse polymer particles having aldehyde groups by seeded aldol condensation polymerization

Submicron-size monodisperse polystyrene/polyglutaraldehyde composite particles having aldehyde groups at the surfaces were produced by seeded aldol condensation polymerization of glutaraldehyde in the presence of polystyrene particles prepared by emulsifier-free emulsion polymerization. This technique is expected to be useful for the production of size-controlled polymer particles having aldehyde groups.Part CXXXVI of the series Studies on Suspension and Emulsion     

Drug-carrying latices for prolonged release of drugs

Dichlorophene was used as a model drug. Drug-carrying latex particles were prepared by soap-free emulsion copolymerization of dichlorophene acrylate with some hydrophilic methacrylate comonomers. The comonomers used affected not only the structure and colloidal stability of particles, but also the drug-activity of particles. Preliminary study of the drug activity revealed that highly hydrophilic latex particles were very stable and too inactive to be engulfed by amoebae and kill them. On the contrary, less hydrophilic particles carrying a large amount of drug can be an effective device to release drugs at a moderate rate to fight against extracelluar targets such as parasites.     

Non-destructive determination of spontaneously fissioning nuclides by neutron coincidence counting using multichannel time spectroscopy

A non-destructive method for determining the amount of actinoids has been developed. The method is based on thermal neutron coincidence counting and employs a selective detection of neutrons resulting from the spontaneous fission of actinoids. The detection system is described in detail and the measurement results of²⁴⁴Cm as an example are presented. The results show that the measured fission rate of²⁴⁴Cm is consistent with the fission rate calculated from ENDF/B-V data and that the amount of²⁴⁴Cm can be determined within about 5% accuracy even in the presence of a large amount of actinoids, for example, up to 2.6·10⁶, 3.6·10⁴, or 1.6·10³ times in the mass ratio of²³⁹Pu,²⁴¹Am, or²⁴⁰Pu to²⁴⁴Cm, respectively.     

Tribological properties of ormosil coatings

Transparent plastics are not scratch resistant. The damage leads to a loss of optical properties. Coatings prepared using either tetraethoxysilane or colloidal silica particles embedded in glymo is a way to avoid these disadvantages. Tribological experiments are carried out to better understand the surface modification due to a sliding friction. It is shown that the wear track is not directly related to usual mechanical properties such as Young's modulus and the hardness of the coating. The different stages leading to material loss are discussed in term of particle removal and debris circulation (accumulation or elimination) through the friction track. The mechanical properties of the film combined with the film to substrate adhesion are expected to play an important role as it can be deduced from results obtained as a function of the coating composition.