Permeability and conductivity of red blood cell templated polyelectrolyte capsules coated with supplementary layers

The permeability of ions and small polar molecules through polyelectrolyte multilayer capsules templated on red blood cells was studied by means of confocal microscopy and electrorotation. Capsules were obtained by removing the cell after polyelectrolyte multilayer formation by means of NaOCl treatment. This procedure results in cross-linking of poly(allylamine hydrochloride) (PAH) molecules and destroying poly(styrene sulfonate) (PSS) within the multilayer. Capsules are obtained being remarkably different from layer-by-layer (LbL) capsules. These capsules are rather permeable for low as well as for high molecular weight species. However, upon adsorption of extra polyelectrolyte layers the permeability decreased remarkably. The assembly of six supplementary layers of PAH and PSS rendered the capsule almost impermeable for fluorescein. Resealing by supplementary layers is a potential means for filling and release control. By means of electrorotation measurements, it was shown that the capsule walls obtained isolating properties in electrolyte solutions. Conclusions are drawn concerning the mechanism of permeability through cell templated polyelectrolyte multilayer capsules.     

Formation of two reaction zones in flow-injection systems for kinetic determinations of cobalt and nickel

The injection of a large sample volume (ca. 1 ml) into a single-channel flow-injection system was studied with a dye (to examine physical dispersion) and with chemical systems having easily-controlled reaction rates (to examine chemical kinetics). With the dye, the response curve has a central plateau caused by non-mixing of carrier and sample. When a chemical reaction takes place, two peaks are obtained with a central minimum corresponding to little or no mixing and reaction. Comparison of these two types of response provides relationships of analytical interest between response parameters and variables in te flow-injection system. The configuration is used for individual kinetic determinations of cobalt and nickel (2.5–30 μg ml^?1 based on the rate of their complex formation with 2-hydroxybenzaldehyde thiosemicarbazone. Sample injection rates were 15 h^?1 for cobalt and 40 h^?1 for nickel. Differential kinetic determinations of cobalt and nickel in mixtures are based on the increment in peak height (or area) between the two peaks obtained for each injection; sample throughput is 7 h^?.     

Inclusion Complexes of Gossypol with 2-Pentanone, 3-Pentanone,and 2-Hexanone

Inclusion complexes of gossypol with 2-pentanone, 3-pentanone, and 2-hexanone were prepared by crystallization from the corresponding ketone and hexane, and their structures were determined by low-temperature X-ray diffraction. All three compounds crystallize in monoclinic systems and have a 2:1 gossypol-to-solvent molar ratio. Both gossypol–pentanone complexes crystallize in C2/c space groups, and the solvent cavities in these structures have C₂ symmetry. The 3-pentanone molecule, which has C₂ symmetry, sits symmetrically within the cavity, while the 2-pentanone molecule, which lacks C₂ symmetry, takes two equally probable orientations within the cavity. Both structures are similar to previously reported gossypol inclusion complexes formed with small esters and 3-hexanone. The distal positioning of the carbonyl group in 2-hexanone does not allow it to fit into the same solvent cavity that exists in the pentanone structures. In the gossypol-2-hexanone complex, the solvent cages are skewed, and the C₂ site symmetry is lost. As a result, the structure crystallizes in a Cc space group and has a larger asymmetric unit and unit cell. Although the 2-hexanone structure retains many of the features of the gossypol–pentanone complexes, this is the first report of a gossypol inclusion compound with this extended structure.This revised version was published online in July 2005 with a corrected issue number.     

Synthesis, structures, and magnetic properties of novel mononuclear, tetranuclear, and 1D chain Mn(III) complexes involving three related asymmetrical trianionic ligands

The manganese(III) complexes studied in this report derive from asymmetrical trianionic ligands abbreviated H(3)L(i) (i = 4-6). These ligands are obtained through reaction of salicylaldehyde with "half-units", the latter resulting from monocondensation of different diamines with phenylsalicylate,. Upon deprotonation, L(i) (i = 4-6) possess an inner N(2)O(2) coordination site with one amido, one imine, and two phenoxo functions, and an outer amido oxygen donor. The trianionic character of such ligands yields original neutral complexes with the L/Mn stoichiometry. The crystal and molecular structures of three complexes have been determined at 190 K (1) or 180 K (2 and 3). Complex 1 crystallizes in the triclinic space group P (No. 2): a = 7.8582(14) A, b = 10.9225(16) A, c = 12.4882(18) A, alpha = 67.231(14) degrees, beta = 72.134(14) degrees, gamma = 82.589(13) degrees, V = 940.6(3) A(3), Z = 2. Complex 2 crystallizes in the orthorhombic space group Pbcn (Nuomicron. 60): a = 23.8283(15) A, b = 11.1605(7) A, c = 26.152(2) A, V = 6954.8(8) A(3), Z = 8, while complex 3 crystallizes in the monoclinic space group P2(1)/c (No. 14) with a = 11.7443(14) A, b = 7.5996(10) A, c = 18.029(2) A, beta = 100.604(10) degrees, V = 1581.6(3) A(3), Z = 4. Owing to hydrogen bonds and pi-pi stackings, the mononuclear neutral molecules of 1 are arranged in a 2D network while complexes 2 and 3 are tetranuclear and polymeric (1D chain) species, respectively, owing to the bridging ability of the oxygen atom of the amido function. The experimental magnetic susceptibilities of complexes 2 and 3 indicate the occurrence of similarly weak Mn(III)-Mn(III) antiferromagnetic interactions (J = -1.1 cm(-1)). Single ion zero-field splitting of manganese(III) must be taken into account for satisfactorily fitting the data by exact calculation of the energy levels associated to the spin Hamiltonian through diagonalization of the full matrix for axial symmetry in 2 (J = - 1.1 cm(-1), D(1) = 2.2 cm(-1), D(2) = -2.8 cm(-1)), D(1) and D(2) being associated to the six- and five-coordinate Mn ions, respectively. A weaker antiferromagnetic interaction (J = - 0.2 cm(-1)) operates through pi-pi stacking in complex 1. Complex 3 is a weak ferromagnet (ordering temperature approximately 7 K) as a result of the spin canting originating from the crystal packing.     

Synthesis and self-assembly of functionalized donor-sigma-acceptor molecules

[structure: see text] 3,5,7-Tris(arylmethyl)-1-aza-adamantanetrione donor-sigma-acceptor compounds have been synthesized in four steps. Computational and (1)H NMR analyses rationalize the solubility, gelation, and conformational properties of the C3-symmetric molecules toward employing sigma-coupled donor-acceptor interactions in molecular self-assembly.     

Palladium catalyzed amination of vinyl chlorides: a new entry to imines, enamines and 2-amino-1,3-butadienes

Vinyl chlorides are employed for the first time in palladium catalyzed cross-coupling reactions with amines to furnish imines and enamines. The new methodology has been applied to the synthesis of 2-amino-1,3-butadienes, that could not be achieved from the corresponding bromides.     

Investigation of a resorcinol–formaldehyde resin by 13C-NMR spectroscopy and intrinsic viscosity measurement

Various molecular weight fractions and oligomers isolated from a novolac type resorcinol–formaldehyde (RF) wood adhesive resin were studied by ¹³C-NMR, gel permeation chromatography (GPC), and intrinsic viscosity measurements. The ¹³C-NMR results indicate that methylene groups occur mostly between C₄–C′₄ and C₂–C′₄ carbons and in minor amounts between C₂–C′₂ carbons of resorcinol rings. By suppressing the nuclear Overhauser effect (nOe) and using a long delay time for ¹³C-NMR measurements, reasonable methylene/aromatic carbon ratios were obtained from the aromatic C₁ carbon patterns that have resulted from different numbers of methylene groups bonded on the aromatic ring. This analysis results indicate that the RF resin has an appreciable amount of branch structures and compare favorably with the gel permeation chromatography and intrinsic viscosity measurement results. © 1993 John Wiley & Sons, Inc.     

Intramolecular carbolithiation reactions for the preparation of Azabicyclo

Tin-lithium exchange and intramolecular carbolithiation (anionic cyclization) have been used to construct the three nitrogen-positional isomers of the azabicyclo[2.2.1]heptane ring system. The 7-azabicyclo[2.2.1]heptane ring system is accessed from either diastereomer of a 2,5-disubstituted pyrrolidine, via a chiral organolithium intermediate. The 2-azabicyclo[2.2.1]heptane ring system is formed stereoselectively in low yield by a tandem cyclization, together with the product from monocyclization. Better yields of the 2-aza ring system can be obtained using an alternative approach from a 2-tributylstannyl-4-allylpyrrolidine, despite the trans arrangement of the tin (and, hence, lithium) atom and the allyl unit. The 1-azabicyclo[2.2.1]heptane ring system is accessed in just three steps from 4-piperidone.     

Higher-alcohols biorefinery

The concept of a biorefinery for higher-alcohol production is to integrate ethanol and methanol formation via fermentation and biomass gasification, respectively, with, conversion of these simple alcohol intermediates into higher alcohols via the Guerbet reaction. 1-Butanol results from the selfcondensation of ethanol in this multistep reaction occurring on a single catalytic bed. Combining methanol with ethanol gives a mixture of propanol, isobutanol, and 2-methyl-1-butanol. All of these higher alcohols are usefulas solvents, chemical intermediates, and fuel additives and, consequently, have higher market values than the simple alcohol intermediates. Several new catalysts for the condensation of ethanol and alcohol mixtures to higher alcohols were designed and tested under a variety of conditions. Reactions of methanol ethanol mixtures gave as high as 100% conversion of the ethanol to form high yields of isobutanol with smaller amounts of 1-propanol, the amounts in the mixture depending on the starting mixture. The most successful catalysts are multifunctional with basic and hydrogen transfer components.