Coordination polymers of copper(II) with some dicarboxysiloxane ligands

Several new coordination polymers of copper(II) with different carboxylate ligands containing siloxane units were synthesized by equilibrium polycoordination reactions of copper(II) acetate with the proper dicarboxylic acid (i.e. 1,3‐bis(3‐carboxypropyl)tetramethyldisiloxane, α,ω‐bis(3‐carboxypropyl)oligodimethylsiloxane, and 1,3‐bis(sebacomethyl)tetramethyldisiloxane) in solution (methanol), at room temperature. Some variations in the feed molar ratios were made. The resulting polymers having a polycoordination degree between 5 and 71 are soluble in a wide range of common organic solvents. The formation of polymers was proved by IR and UV–VIS absorption spectroscopy. The thermal behaviour of the coordination polymers was analysed by thermogravimetry in air. The silicon and copper contents and inherent viscosities were also determined. Copyright © 2002 John Wiley & Sons, Ltd.     

Zero sets of polynomials: one versus two variables

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Zero sets of polynomials: one versus two variables

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Progresses in treatment of collagen and keratin-based materials with silver nanoparticles

The treatment of chromium tanned sheepskins with poly(hydroxyl urethane) and dispersion of chemically synthesized nanosilver showed the best resistance to fungi and bacterial exposure tests. These collagen-based materials containing different amounts of nanosilver were investigated by Atomic Absorption Spectroscopy, Atomic Force Microscopy and Scanning Electron Microscopy coupled with Energy Dispersive X-Ray Spectroscopy. The influence of sheepskins treated with silver nanoparticles on the wound healing process was assessed and the nanoparticles concentration seems to have a positive effect up to 370 ppm and does not influence the inflammatory process above this concentration.     

About the Mulliken electronegativity in DFT

In the framework of density functional theory, a new formulation of electronegativity that recovers the Mulliken definition is proposed and its reliability is checked by computing electronegativity values for a large number of elements. It is found that the obtained values, which are compared with previously proposed electronegativity scales, fulfill the main periodic criteria.     

Incorporation of siloxanes in hydrolytically degradable structures: I. Poly(anhydride)s synthesis

New poly(anhydride)s containing amino acids and siloxane segments have been synthesized. The synthetic method involves the polycondensation in solution of the organic diacids (N-trimellitylimidoglycine, 1a, N-trimellitylimido-γ-aminobutiric acid, 1b, and N-trimellitylimido-ε-aminocapronic acid, 1c) obtained from the proper amino acids with a siloxane diacid (1,3-bis(3-carboxypropyl)tetramethyldisiloxane, 2a, α,ω-bis(3-carboxypropyl)oligodimethylsiloxane, 2b, or 1,3-bis(sebacomethyl)tetramethyl-disiloxane, 2c). The acetylation method was used for the activation of the two types of diacids (organic and siloxanic). Optimization of synthesis parameters was made.The structures and morphology of partial and final products were determined by IR and ¹H NMR spectroscopy and differential scanning calorimetry. Inherent viscosities were determined and some preliminary solubility and hydrolytic stability tests were also performed.     

Synthesis,characterization, and catalytic activity of N-heterocyclic carbene (NHC) palladacycle complexes

Palladacycle dimers possessing bridging halides can be easily cleaved by using N-heterocyclic carbenes (NHCs) to generate novel monomeric complexes. The structure of one of these was determined by single-crystal diffraction study and consists of a square-planar coordination around the palladium center where the NHC ligand is trans to the amine of the palladacycle. The complex was found to be equally active in aryl amination and alpha-arylation of ketones even at very low catalyst loading (0.02 mol %). Primary and secondary alkyl/arylamines are equally active partners in coupling reactions. [reaction: see text]     

New poly(amide-imide) siloxane copolymers by polycondensation

Some new poly(amide-imide) siloxane copolymers have been synthesized by solution polycondensation of some aromatic diamines with siloxanic diacids having preformed imide rings. Two polycondensation techniques were used: polycondensation of aromatic diamines with diacid chlorides and direct polycondensation of aromatic diamines with diacids in the presence of organic phosphites, following the Yamazaki-Higashi phosphorylation technique. In all cases the reactions were carried out using equimolecular amounts of the two monomers, in polar aprotic solvents and inert atmosphere.The obtained compounds were characterized by elemental C, H and Si analysis, solubility tests, IR and ¹H-NMR spectrometry. Thermogravimetric curves were also recorded. All data agree with the proposed structures.