Salt-induced aggregation in cationic liposome aqueous suspensions resulting in multi-step self-assembling complexes

The interaction of uni-univalent salt with cationic liposomes in aqueous suspension has been investigated by means of dynamic light scattering measurements and the hydrodynamic radius of the resulting aggregates has been evaluated for different ionic strengths. We observe the simultaneous presence of two different steady-state structures, in the 100–500 nm and 5 μm range, respectively, whose relative concentrations depend on the salt content. This behavior differs from that observed in usual charge stabilized colloidal suspensions and that giving rise to lipoplex formation in presence of polynucleotides. This peculiar behavior is briefly discussed in the light of Derjaguin–Landau–Verwey–Overbeek (DLVO) colloidal stability theory.     

Synthesis of polyanionic glycopolymers for the facile assembly of glycosyl arrays

Polyanionic glycopolymers were synthesized aiming at establishing a simple process for assembling glycosyl arrays. The synthetic glycopolymers carry the key carbohydrate epitopes of α-d-galactobioside (Gb₂), β-lactoside, and α-d-mannopyranoside, each of which serves as a ligand of bacterial toxins and adhesion proteins. The Gb₂ epitope, prepared from penta-O-acetyl-d-galactopyranose, was coupled with poly(ethylene-alt-maleic anhydride) in a polymer reaction to afford a Gb₂-embedded glycopolymer having also carboxylate (COO⁻) polyanions at the side chain. The polyanionic glycopolymer was then applied to a preparation of sugar-coated gold electrodes, which involves an alternating layer-by-layer adsorption based on electrostatic interactions. The presence of the Gb₂-coat on the surface was evidenced by Fourier transform infrared reflection absorption spectroscopy. The Gb₂-coated glyco-chip was stable in 10 mM HEPES buffer containing 150 mM NaCl aq. Other glycopolymers carrying the β-lactoside and α-d-mannopyranoside epitopes were applied to the same assembling process. The derived glycosyl arrays will be useful for detecting Shiga toxins, other pathogenic toxins and viruses when applied as glyco-chips for surface plasmon resonance or quartz crystal microbalance technique.     

A Novel One‐Dimensional Copper Mellitate Complex Featured by {Cu(H2O)2(urea)[C6(COO)4(COOH)2]}n2n– Polyanions

Blue monoclinic single crystals of the novel one‐dimensional [H₃N‐(CH₂)₆‐NH₃][Cu(H₂O)₂(urea)(μ₂‐C₆(COO)₄(COOH)₂)] · H₂O coordination polymer were prepared in aqueous solution at room temperature in the presence of 1,6‐diaminohexane and urea [space group P2₁/n (no. 14) with a = 958.48(9), b = 1465.74(11), c = 1821.14(12) pm, β = 97.655(8)°]. The Cu²⁺ cation is coordinated in a square pyramidal manner by two oxygen atoms stemming from the dihydrogen mellitate tetraanion, one oxygen atom from the urea molecule, and two water molecules. The Cu–O distances are in the range of 193.3(2) and 229.4(2) pm. The connection between Cu²⁺ and [C₆(COO)₄(COOH)₂]^4– yields infinite chain‐like polyanions parallel to [1$\bar{}$ 01] with a composition of {Cu(H₂O)₂(urea)[C₆(COO)₄(COOH)₂]}_n^2n–. The dihydrogen mellitate tetraanion adopts a μ₂ coordination mode. The [(H₃N–(CH₂)₆–NH₃)]²⁺ cations are accommodated between the chains as counter cations. The hexane‐1,6‐diammonium cations adopt a partial synclinal conformation. The chains are connected by strong and weak hydrogen bonds. Magnetic measurements reveal a paramagnetic Curie‐Weiss behavior and a magnetic moment of 1.93 μ_B per Cu²⁺. Thermoanalytical investigations in air show that the complex is stable up to 135 °C, and the following decomposition processes yield CuO.     

The [Ag{Se2C2(CN)2}(Se6)]3−, [Sb{Se2C2(CN)2}2]3−, and [As(Se)3(CH2CN)]2− Anions: Facile Formation of the Maleonitrilediselenolate (mns) Ligand, [Se2C2(CN)2]2−

An unusual route to the maleonitrilediselenolate (mns) ligand has been discovered with the isolation of compounds that contain this ligand bound to silver (structure shown on the right) or antimony. The formation of the [As(Se)₃(CH₂CN)]²⁻ anion along with possible pathways to the mns ligands is discussed.     

A Five-Membered Ring with Three Negative Charges and Solvent-Free Lithium Counterions

Remarkably short distances to the ring plane are shown by the η⁵-bound lithium ions in the first compound with a triply negatively charged five-membered ring, 1 , which was obtained by reduction of 2 with lithium. R=CH(SiMe₃)₂, Dur=2,3,5,6-tetramethylphenyl.     

Efficient synthesis of phosphorus-containing dendrimers capped with isosteric functions of amino-bismethylene phosphonic acids

An efficient synthetic strategy to synthesize phosphorus-containing dendrimers capped with isosteric acid functions derived from tyramine is described. The method is demonstrated on a first generation dendrimer that can be easily capped with 12 amino(bismethylene) sulfonic acids and amino(bismethylene) carboxylic acids that are strict analogs of the corresponding amino(bismethylene) phosphonic acids.     

The strong influence of small amounts of palladium on the structure of liquid potassium-thallium

Neutron diffraction measurements on liquid KT1 alloys with 0, 1, and 5 at % Pd, respectively, show that the prepeak in the structure factor shifts from wave vector k=8.0 to 7.2 nm⁻¹ with an increasing amount of Pd. This corresponds to a periodicity change from 0.96 to 1.07 nm in real space². The structure of the liquid KT1 alloys is compared to the corresponding crystal structures, and some similarities are observed. Reverse Monte Carlo modelling indicates T1 clustering in the liquid alloy. Also in solid KTl Tl-clusters occur. The distance between the clusters increases with the addition of 5%. Pd. More information is needed to discriminate between various possible structures of the Tl clusters in the liquid alloy and to determine the position of Pd in these clusters.     

Ethyltrimethylammoniumpentaiodid (EtMe3N)I5

Studies on Polyhalides. 40. Ethyltrimethylammonium Pentaiodide (EtMe₃N)I₅ (EtMe₃N)I₅ has been prepared by the reaction of stoichiometric amounts of ethyltrimethylammonium iodide and iodine in methanol. It crystallizes in the orthorhombic space group Pna2₁ with a = 1011.3(1) pm, b = 1255.3(2) pm, c = 1237.7(2) pm and Z = 4. The anionic iodine partial structure is composed of puckered layers which may be derived by deforming a quadratic net with iodide ions in the knots and iodine molecules on the edges of the meshes.     

Syntheses,Crystal Structures,and Reactivity of [enH]4[Sn2Se6]·en, [enH]4[Sn2Te6]·en and [enH]4[Sn2S6]: Known Anions within Novel Coordination Spheres obtained by Novel Synthesis Routes

The hexachalcogenodistannates K₆[Sn^III₂Se₆] or Li₄[Sn^IV₂Te₆]·8en were recently reported to simultaneously act as mild oxidants and chalcogenide sources in reactions with CoCl₂/LiCp* (Cp* = pentamethylcyclopentadienide) while the Sn—E (E = Se, Te) fragment is not kept in the products, e.g. [(Cp*Co)₃(μ₃‐Se)₂], [(Cp*Co)₃(μ₃‐Se)₂][Cl₂Co(μ₂‐Cl)₂Li(thf)₂] or [(Cp*Co)₄(μ₃‐Te)₄]. In search of related reagents with possibly different reaction behavior, we isolated and crystallographically characterized isotypic compounds [enH]₄[Sn^IV₂Se₆]�en ( 1 ), and [enH]₄[Sn^IV₂Te₆]·en ( 2 ) (en = 1, 2‐diaminoethane), that result from an uncommon disproportion/re‐arrangement reaction: distannate(III) K₆[Sn₂E₆] (E = Se, Te) was reacted with en·2HCl to yield 1 or 2 under disproportion of Sn^III to Sn^II and Sn^IV. Another pathway was necessary to synthesize the respective but solvent‐free thiostannate [enH]₄ [Sn^IV₂S₆] ( 3 ), since the phase “K₆[Sn₂S₆]” is unknown. This second method started out from SnCl₄·2THF and S(SiMe₃)₂ in en solution. However, using E(SiMe₃)₂ (E = Se, Te) instead of S(SiMe₃)₂, 1 and 2 are also obtained this way. 1—3 are the first chalcogenostannates that exhibit exclusively [enH]⁺ counterions. The compounds were characterized by means of X‐ray crystallography and NMR spectroscopy. They seem to be suitable for reactions towards group 8‐10 metal complexes. Preliminary experiments indicate that the binary anions 1 — 3 coordinated by 1‐aminoethylammonium ions react more slowly compared to the anionic phases tested until now.     

Synthesis and Characterization of the Ternary Thiobismuthates A9Bi13S24 (A = K,Rb)

Ternary alkali metal thiobismuthates A₉Bi₁₃S₂₄ (A = K, Rb) were synthesized by direct combination reactions at 650 °C. The compounds crystallize in the monoclinic space group C2/m (no. 12) with cell parameters a = 30.919(1) Å, b = 4.1008(2) Å, c = 20.9072(9) Å, β = 105.826(3)° for K₉Bi₁₃S₂₄ ( 1 ) and a = 31.823(6) Å, b = 4.1177(8) Å, c = 21.086(4) Å, β = 105.62(3)° for Rb₉Bi₁₃S₂₄ ( 2 ). The crystal structure of 1 contains a 3D [K₂Bi₁₃S₂₄]^7– polyanionic framework, whereas 2 consists of 2D [RbBi₁₃S₂₄]^8– polyanionic slabs stacked along [201]. Both 1 and 2 are semiconductors with a band gap of 1.4 and 1.3 eV, respectively, which is supported by an electronic structure calculation. 1 melts congruently at 580 °C, while 2 melts incongruently at 575 °C. 1 and 2 are airstable and insoluble in water and organic solvents.