Sorbents based on N-(2-carboxyethyl)chitosan cross-linked by nanosecond electron beams

Methods for the synthesis of new chelating chitosan derivatives containing 2-carboxyethyl groups were developed. Their macromolecules were cross-linked by the irradiation with a nanosecond electron beam, which gave for the first time sorbents with a high sorption capacity for Cu^II ions. The maximum sorption capacity, which is achieved in the pH range 6.5–7.2. and the Langmuir adsorption constant of Cu²⁺ ions on the sorbent with the degree of substitution 0.91 are 1.37 mmol g^?1 and 152.51 L mol^?1, respectively. The structures of the formed complexes in the sorbent phase were characterized by ESR spectroscopy.     

Complexes of mono- and bis(2-carboxyethyl)-2-picolylamine: Synthesis and crystal and molecular structures

N-(2-Pyridylmethyl)iminodipropionic (I) and N-(2-pyridylmethyl)-3-aminopropionic acids (II) were obtained. A reaction of acid I with a Cu(II) salt gave a 2: 2 complex (III); a reaction of acid II with a Ni(II) salt yielded a 1 : 2 complex (IV). The crystal structures of these complexes were determined by X-ray diffraction. The abilities of compounds I and II to form complexes were compared with the literature data for other ligands containing the N-(2-pyridylmethyl)amino fragment. The structural features of the chelate complexes with 2-aminomethylpyridine derivatives were revealed, depending on the other substituents and the metal center.     

Palladium complex of 6-(2-hydroxy-5-methylphenyl)-3-(pyridin-2-yl)-1,2,4-triazin-5(2<Emphasis Type="Italic">H</Emphasis>)-one: Synthesis,structure, and catalytic activity

Palladium(II) complex with 6-(2-hydroxy-5-methylphenyl)-3-(pyridin-2-yl)-1,2,4-triazin-5(2H)-one was synthesized for the first time. The ligand was prepared from 3-(pyridin-2-yl)-1,2,4-triazin-5(2H)-one and 4-methylphenol via nucleophilic substitution of hydrogen (S_N^H reaction). The complex was readily soluble in basic medium, and it effectively catalyzed Mizoroki-Heck reaction.     

Synthesis and surface structural characteristics of new polysiloxane xerogel

Pyridylethylaminopropylpolysiloxane xerogel (PEAPPSX) was synthesized by sol-gel technology. The composition of the substance was determined via elemental analysis and 1H NMR spectroscopy. The surface structural characteristics of the xerogel were determined by electron microscopy and low-temperature nitrogen sorption; thermal analysis was also performed. It was established that the content of functional groups in PEAPPSX was 2.43 mmol/g, and that xerogel is a mesoporous substance with a developed surface (121.71 m²/g).     

<Emphasis Type="Italic">N</Emphasis>-(2-(2-Pyridyl)ethyl)chitosan (PEC) for Pd(II) and Pt(IV) sorption from HCl solutions

Chitosan was modified by grafting 2-pyridyl-ethyl moieties on the biopolymer backbone for the synthesis of a Platinum Group Metal (PGM) sorbent. The sorbent was tested for Pd(II) and Pt(IV) sorption from HCl solutions. Stable for HCl concentrations below 0.5 M, the sorbent reached sorption capacities as high as 3.2 and 2.6 mmol metal g⁻¹ for Pd(II) and Pt(IV), respectively. Metal sorption mainly proceeds by electrostatic attraction in acidic solutions, though a contribution of complexation mechanism cannot be totally rejected. The resistance to intraparticle diffusion is the main controlling mechanism for uptake kinetics. While agitation speed has a limited effect on kinetics, metal concentration and sorbent dosage have a greater effect on the kinetic profiles. The intraparticle diffusivity varies between 3 × 10⁻¹¹ and 4.5 × 10⁻¹⁰ m² min⁻¹. Thiourea (combined with HCl solution) is used for Pd(II) and Pt(IV) desorption. The resin could be desorbed and recycled for a minimum of five cycles maintaining high efficiencies of sorption and desorption.     

Bis[N‐(2‐hydroxy­ethyl)‐β‐alaninato]copper(II)

The Cu^II ion in the title complex, [Cu(C₅H₁₀NO₃)₂] or [Cu(He‐ala)₂] [He‐ala = N‐(2‐hydroxy­ethyl)‐β‐alaninate], resides at the inversion centre of a square bipyramid comprised of two facially arranged tridentate He‐ala ligands. Each He‐ala ligand binds to a Cu^II ion by forming one six‐membered β‐alaninate chelate ring in a twist conformation and one five‐membered ethanol­amine ring in an envelope conformation, with Cu—N = 2.017 (2) Å, Cu—O_COO = 1.968 (1) Å and Cu—O_OH = 2.473 (2) Å. The [Cu(He‐ala)₂] mol­ecules are involved in a network of O—H⋯O and N—H⋯O hydrogen bonds, forming layers parallel to the (10) plane. The layers are connected into a three‐dimensional structure by van der Waals inter­actions, so that the mol­ecular centres form pseudo‐face‐centered close packing.     

Reactions of β-amino-β-polyfluoroalkylvinyl ketones with diethylenetriamine. Simple synthesis of 1,4,8-triazabicyclo[5.3.0]dec-4-ene derivatives

β-Amino-β-polyfluoroalkylvinyl aryl(hetaryl) ketones react with diethylenetriamine to form derivatives of a new 1,4,8-triazabicyclo[5.3.0]dec-4-ene system. Published inIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1432–1435, August, 2000.     

Thiocarbamoyl chitosan as a novel sorbent with high sorption capacity and selectivity for the ions of gold(III), platinum(IV), and palladium(II)

Thiocarbamoyl chitosan (TCC) was synthesized by grafting thiourea on chitosan backbone in eutectic composition of ammonium thiocyanate—thiourea. Insoluble products with the amno group functionalization degree of 0.3–1.1 can be prepared by varying the conditions of polymer-analogous (synthesis in a gel) transformation. Structure of the synthesized chitosan derivatives was characterized by elemental analysis, diffuse reflectance infrared spectroscopy, and the solid state ¹³C NMR. Study of sorption properties of TCC shows high sorption capacity and selectivity for the ions of gold(III), platinum(IV), and palladium(II) as evidenced by results obtained at pH 2 in the presence of 100–1000-fold excess of iron(III), copper(II), zinc(II), and nickel(II). Sorption capacity of TCC for all ions increases with the increase in the degree of substitution and changes in the series: Au^III > Pd^II > Pt^IV.     

Gel-synthesis, structure, and properties of sulfur-containing chitosan derivatives

The possibility of using the thermochemical approach to thermal decomposition of solids, previously developed by the author, to interpretation of the mechanism and kinetics of reduction of metal oxides with hydrogen was studied. Many properties of NiO reduction with hydrogen, including formation of metal nuclea, the nature of induction period, autocatalysis effect, equimolar and isobaric periods of reduction, the character of the effect of hydrogen pressure on reduction rate, and the nanocrystalline structure of a reduced metal, were explained in terms of the given approach.     

Crystal structure of <Emphasis Type="Italic">N</Emphasis>-(3-hydroxypropyl)-β-alanine and Bis(<Emphasis Type="Italic">N</Emphasis>-(3-hydroxypropyl)-β-alaninato)dicopper(II) [Cu<Subscript>2</Subscript> (Pro-ala)<Subscript>2</Subscript>]

N-(3-Hydroxypropyl)-β-alanine was synthesized by the reacti on of 3-aminopropanol with acrylic acid. From this ligand and basic copper carbonate, bis(N-(3-hydroxypropyl)-β-alaninato)dicopper(II) [Cu₂ (C₆H₁₁NO₃)₂] was obtained. The structures of the chelating agent and the copper complex were studied by X-ray diffraction. The Cu(II) coordination polyhedron is a distorted square pyramid. Each ligand forms six-membered β-alaninate and propanolamine chelate rings. The propoxy group functions as a bridge. In the crystal structure, the molecules form intermolecular coordination bonds C=O→Cu, which are perpendicular to the layers. The EPR signal typical of dimeric copper complexes is not observed due to low occupancy of the excited paramagnetic triplet state. The weak paramagnetic signal from monomeric copper complex allowed recording of the ¹H NMR spectrum of [Cu₂ (Pro-ala) ₂] with characteristic line broadening and contact shift. It follows from the obtained data that on dissolution, the complex dissociates by 40% to give monomeric copper complexes.