Electrochemical synthesis of nanocomposite of palladium nanoparticles with polymer viologen-containing nanocapsule

An efficient mediated electrosynthesis of the spherical (85 nm) nanocomposite material Pd@p(MVCA⁸⁺-co-St) was carried out in an aqueous medium. Ultrasmall palladium nanoparticles (3—8 nm) are stabilized in nanocapsules of water-soluble nanoparticles of the copolymer p(MVCA⁸⁺-co-St) consisting of tetraviologen calix[4]resorcinol (MVCA⁸⁺) with styrene (St). The role of the mediator is played by viologen units of a polymer nanoparticle at potentials of the MV²⁺/MV^?+ redox couple. The high catalytic activity of the nanocomposite material in the reduction of nitrophenol with sodium borohydride is shown.     

The Complexation Properties of the Water-Soluble Tetrasulfonatomethylcalix[4]resorcinarene toward α-Aminoacids

The flexible bowl-type water-soluble molecule1, consisting of a resorcinol core and fourconvergent tetrasulfonatomethylene groups, existingas a tetraanion in neutral water solution, was studiedas the host molecule for recognition of-aminoacids. Out of 12 examined guestmolecules only those possessing aromatic hydrophobicmoieties or a long hydrophobic chain with a second ionogenic groupform inclusion complexes with 1. The complex formationwas considered with the help of both ¹H NMRand pH-metric titration in a broad range of pH.The role of host and guest geometric complementarity aswell as additional – and hydrophobic interactionsis discussed. The lack of these interactions inaqueous media provides domination of the guestsolvation by water over the 1 : 1 complexformation with 1.     

DFT Calculation of the Structure of the Coordination Unit of Chlrophyll-Containing Proteins

In a DFT/B3LYP study (6-31G(d) basis set), the structure, IR spectra, and thermodynamic parameters of Mg-porphin-imidazole and Mg-khlorin-imidazole complexes, serving as models of the coordination unit of chlorophyll in proteins, have been calculated. When an axial ligand is added, the Mg atom goes out of the plane of the tetrapyrrole macrocycle, the deviation being 0.34 Å. The frequency of the out-of-plane vibrations of Mg in the complexes increased by 50 cm⁻¹, and the frequencies of the two in-plane vibrations decreased by 25 cm^{− 1}–30 cm⁻¹. IR vibrational spectra have been simulated.Original Russian Text Copyright © 2004 by M. D. Elkin, O. D. Ziganshina, K. V. Berezin, and V. V. Nechaev__________Translated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 6, pp. 1132–1135, November–December, 2004.     

Cationic polymerization of isoprene in the presence of the TiCl4-trichloroacetic acid catalyst system

Cationic polyisoprene characteristic of different molecular parameters can be obtained with high yields in the presence of the TiCl₄-trichloroacetic acid catalyst system. At low monomer concentrations, polyisoprene has a unimodal molecular-mass distribution. At elevated monomer concentrations, the polydispersity of polyisoprene increases significantly with conversion because of chain transfer to the polymer and branching. As the TiCl₄/trichloroacetic acid ratio in the catalyst and the total concentration of the catalytic complex increase, the average molecular masses of the produced cationic polyisoprene decrease as a result of chain transfer to trichloroacetic acid.     

Self-Organization of Di- and Triglycine Oligopeptides in Thin Films on the Hydrophilic and Hydrophobic Silicon Surface under Exposure to Organic Compounds Vapors

Russian Journal of General Chemistry - The influence of the substrate hydrophobicity degree and of the number of amino acid residues in the oligopeptide molecule on the self-assembly of...     

The Synergistic Extraction of Lanthanide Ions by a Mixture of Calix[4]resorcinarene or its Dimethylamino-, Piperidyl- or Trimethylammoniummethylated Derivatives and 1,10-Phenanthroline in n-Heptanol

The alkylaminomethylatedcalix[4]resorcinarene derivatives, modified bydimethylamino-, piperidyl- and trimethylammoniummoieties, have been synthesised to investigate theirextractability towards lanthanide ions and to comparewith the extractability of calix[4]resorcinarene. Both calix[4]resorcinarene and its derivatives have beenshown to synergistically affect lanthanide ionextraction from neutral aqueous solutions by1,10-phenanthroline through outer-sphere interactionof lanthanide bis-phenanthrolinate cations withdeprotonated forms of calix[4]resorcinarene. Thederivatives with dimethylamino- andpiperidylmethylated moieties are shown to be moreeffective extractants in comparison with theunsubstituted one.     

Atomic-force microscopy of nickel nanoparticles possessing electrocatalytic properties

Surface morphology of highly oriented pyrolytic graphite with electrodeposited nickel nanoparticles was studied by atomic-force microscopy in the presence and absence of ethanol. Voltammetric and atomic-force microscopic data and histograms of particle size distribution were used to evaluate the unit-area catalytic activity of the nanocatalyst in relation to conditions of its preparation.     

Electrochemical control of association and deposition of tetraviologen calix[4]resorcin

The association and deposition of tetraviologen calix[4]resorcin MVCA-C ₅ ⁸⁺ can be controlled using the electrochemical reduction-reoxidation cycle of viologen units. The monomeric MVCA-C ₅ ⁸⁺ was converted into the highly molecular (MVCA-C ₅ ^4+· ) _n associate (π-polymer) by reducing it to the MVCA-C ₅ ^4+· tetra(radical cation) and completely returns to the starting monomeric state by reverse oxidation. The reduction to the neutral state MVCA-C ₅ ⁰ allowed calixresorcin to pass from solution to precipitate and the reverse oxidation led to its returning in solution.     

Controlling the Size and Morphology of Supramolecular Assemblies of Viologen–Resorcin[4]arene Cavitands

A novel class of self‐assembling nanoparticles is formed with viologen–resorcin[4]arene cavitands; the association model is strongly controlled by their hydrophobicity. Interestingly, the cavitand assemblies are designed through click chemistry to form self‐assembled noncovalently connected aggregates through counterion displacement. The iodide and benzoate ions are utilized as strongly polarizable counterions to induce cavitand self‐assembly. The counterion‐mediated decrease in hydrophilicity of the viologen–resorcin[4]arenes is the underlying trigger to induce particle formation. These particles can be used as nanocontainers and find their applications in delivery systems.     

Two-step electrosynthesis and catalytic activity of CoO−CoO • xH2O-supported Ag,Au, and Pd nanoparticles

Russian Chemical Bulletin - Two-step electrosynthesis of CoO-CoO?xH2O-supported metal nanoparticles (MNPs, M = Au, Ag, Pd) was carried out in N,N-dimethylformamide in the absence and in...