The structure and dynamic properties of mixed adsorption and penetration layers of α-dipalmitoylphosphatidylcholine/β-lactoglobulin at water/fluid interfaces

The interfacial tensions of mixed α-dipalmitoylphosphatidylcholine (DPPC)/β-lactoglobulin layers at the chloroform/water interface have been measured by the pendent drop and drop volume techniques. In certain intervals, the adsorption kinetics of these mixed layers was strongly influenced by the concentrations of both protein and DPPC. However, at low protein concentration, C_{β-lactoglobulin}=0.1 mg l⁻¹, the adsorption rate of mixed interfacial layers was mainly controlled by the variation of the DPPC concentration. As C_{β-lactoglobulin} was increased to 0.8 mg l⁻¹, the interfacial activity was abruptly increased, and within the concentration range of C_DPPC=10⁻⁴–10⁻⁵ mol l⁻¹, the DPPC has very little effect on the whole adsorption process. In this case, the adsorption rate of mixed layers was mainly dominated by the protein adsorption. This phenomenon also happened as the protein concentration was further increased to 3.6 mg l⁻¹. When C_DPPC>3 · 10^–5 mol l⁻¹, the adsorption behaviour was very similar to that of the pure DPPC although the protein concentration was changed. The equilibrium interfacial tensions of the mixed layers are dramatically effected by the lipid as compared to the pure protein adsorption at the same concentration. It reveals the estimation of which composition of lipid and protein decreases the interfacial tension. The combination of Brewster angle microscopy (BAM) with a conventional LB trough was applied to investigate the morphology of the mixed DPPC/β-lactoglobulin layers at the air/water interface. The mixed insoluble monolayers were produced by spreading the lipid at the water surface and the protein adsorbed from the aqueous buffer subphase. The BAM images allow to visualise the protein penetration and distribution into the DPPC monolayer on compression of the complex film. It is shown that a homogeneous distribution of β-lactoglobulin in lipid layers preferentially happens in the liquid fluid state of the monolayer while the protein can be squeezed out at higher surface pressures.     

The crystal and molecular structure of trimethyltin(IV) chloride, a chlorine-bridged, linear polymer

The crystal and molecular structure of trimethyltin(IV) chloride has been determined by the heavy-atom technique, and refined to a final R value of 0.041 for 1375 independent reflections (2θ < 53°; Mo-K_a radiation I > 2σ(I)) recorded at 138 ± 2 K on a Nonius CAD-4 counter diffractometer. The crystals are monoclinic with space group I2/c; a 12.541(8), b 9.618(11), c 11.015(11) Å, β 92.62(7)°, Z = 8, D_calcd 1.994 g cm⁻³. The needle crystals are composed of polymeric chains of chlorine atoms bridging non-planar trimethyltin(IV) units at unequal (2.430(2) and 3.269(2) Å) distances. The zig-zag chains are bent at chlorine (angle Sn---Cl Sn 150.30(9)°), but nearly linear at tin (angle Cl---Sn Cl 176.85(6)°) to describe a distorted trigonal bipyramidal geometry at tin with the trimethyltin groups eclipsed. The interchain d(Sn Cl) distances are greater than 4.1 Å. The angles carbon—tin—carbon (mean 117.1(3)°) are larger than tetrahedral, while the angles carbon—tin—chlorine (mean 99.9(2) Å) are smaller, in accord with isovalent hybridization principles, but more severely distorted than in the gas-phase, monomeric structure. The tin—chlorine distance of 2.430(2) Å is also longer than in the gas phase monomer, and the intermolecular contact of 3.269 Å is shorter than in other organotin chloride bridged systems (sum of Van der Waals radii 3.85 Å).     

Ba2(VO2)(PO4)(HPO4)·H2O, a New Barium Vanadium(V) Phosphate Hydrate Containing Trigonal Bipyramidal VO5Groups

The hydrothermal synthesis, single crystal structure, and some physical properties of Ba₂(VO₂)(PO₄)(HPO₄)·H₂O, a new barium vanadium(V) phosphate hydrate, are reported. This phase is built up from one-dimensional chains of unusual VO₅trigonal bipyramids and (H)PO₄tetrahedra, fused together via V–O–P linkages. These anionic chains propagate along the polar [010] direction. 11-Coordinate barium cations and water molecules occupy the interchain regions and link the chains together. Structural data for this phase and other known barium vanadium phosphates are briefly compared. Crystal data: Ba₂(VO₂)(PO₄)(HPO₄)·H₂O,M_r=566.57, monoclinic, space groupP2₁(No. 4),a=5.0772(5) Å,b=8.724(2) Å,c=10.806(1) Å,β=90.795(8)°,V=478.6(1) ų,Z=2,R=2.65%,R_w=2.89% [147 parameters, 1893 observed reflections withI>3σ(I)].     

Piezoelectric Sensor in Situ Monitoring Adsorption of Fibrinogen and Surfactant onto a Self-Assembled Monolayer of Alkanethiols

This report describes the use of a piezoelectric quartz crystal (PQC) sensor to investigate the nonspecific adsorption of fibrinogen (FN) and sodium dodecyl sulfate (SDS) onto a self-assembled monolayer (SAM) of alkanethiols on gold. The change in adsorption mass was monitored in situ by the PQC sensor. A kinetics model was proposed to describe the adsorption of the FN and SDS on the hydrophobic SAM surface. The adsorption kinetics parameters were determined from the responses of the PQC. The adsorption and desorption rate constants of the FN on the SAM surface were estimated to be (6.18 ± 0.53) × 10³ M⁻¹ s⁻¹ and (6.74 ± 0.72) × 10⁻³ s⁻¹, respectively. The rate constants for the adsorption and desorption of SDS on the SAM are (24.3 ± 1.4 M⁻¹ s⁻¹) and (1.52 ± 0.11) × 10⁻² s⁻¹, respectively. The adsorption of SDS on the SAM was reversible. The fractional coverage of the FN on the SAM surface was estimated from kinetics analyses to be 42–86% for the FN concentration range 25–400 μg/ml. Over 80% of the FN is irreversibly adsorbed on the SAM surface with respect to dilution of the bulk phase. The fraction of FN reversibly adsorbed increases with the bulk concentration of FN.     

Surface tension and adsorption behavior of mixtures of diacyl glycerol arginine-based surfactants with DPPC and DMPC phospholipids

The binary surface interactions of some novel cationic diacyl glycerol arginine-based surfactants with model phospholipids, which are often used as model membrane components, are studied at 25 °C in aqueous solutions of 0.1 M sodium chloride. The surfactants are 1,2-dimyristoyl-rac-glycero-3-O-(N^α-acetyl-l-arginine) hydrochloride (1414RAc) and 1,2-dilauroyl-rac-glycero-3-O-(N^α-acetyl-l-arginine) hydrochloride (1212RAc), and they are important as potential antimicrobial agents which are biodegradable and with less toxicity than other cationic surfactants. The phospholipids are 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC) and 1,2-dimyristoyl-sn-glycero-3-phosphatidylcholine (DMPC). The equilibrium and dynamic surface tension of each surfactant, each phospholipid, and some of their binary mixtures are studied using the bubble surfactometry method at constant area or pulsating area conditions. In addition, the surface densities of pure and mixed monolayers of these compounds at the air/water interface are probed with infrared reflection–absorption spectroscopy (IRRAS). Steady state and dynamic surface tension synergism, or antisynergism in one case, and synergistic adsorption effects are detected for the mixed dispersions studied. The enhanced adsorption detected with IRRAS, and the enhanced dynamic and steady state surface tension lowering indicate strong miscibility and net attractive interactions between the compounds in the adsorbed mixed monolayers.     

Biosorption of nickel from aqueous solutions by Acacia leucocephala bark: Kinetics and equilibrium studies

The biosorption of nickel(II) ions from aqueous solution by Acacia leucocephala bark was studied in a batch adsorption system as a function of pH, initial metal ion concentration, adsorbent dosage, contact time and temperature. The maximum Ni(II) adsorption was obtained at pH 5. Further, the biosorbents were characterized by Fourier Transformer Infrared Spectroscopy (FTIR). The experimental data were analysed using three sorption kinetic models viz., the pseudo-first- and second-order equations and the intraparticle diffusion model. Results show that the pseudo-second-order equation provides the best correlation for the biosorption process. The equilibrium nature of Ni(II) adsorption at different temperatures of 30, 40 and 50 °C have been described by the Langmuir and Freundlich isotherm models. The equilibrium data fit well Langmuir isotherm. The monolayer adsorption capacity of A. leucocephala bark as obtained from Langmuir isotherm at 30 °C was found to be 294.1 mg/g. The Chi-square (χ²) and Sum of the square errors (SSE) tests were also carried out to find the best fit adsorption isotherm and kinetic model. Isotherms have been used to determine thermodynamic parameters of the process, viz., free energy change (ΔG°), enthalpy change (ΔH°), and entropy change (ΔS°) were calculated indicating that this system was a spontaneous and endothermic process. Present investigation emphasized that A. leucocephala bark may be utilized as a low cost adsorbent for nickel removal.     

Variations in the Charge and Open-Circuit Potential of a Platinum Electrode during Adsorption of Iodine and Iodide Ions

The adsorption of iodine and iodide anions on a Pt/Pt electrode (0.5 M H₂SO₄ as a supporting solution) is compared using potentiodynamic and galvanostatic charging curves, transients of the current and open-circuit potential (OCP), and analytical measurements. Variations in the charge and OCP during the adsorption obey relationships derived for strong adsorption of neutral species and ions on a hydrogen electrode with the formation of irreversibly adsorbed atoms. The main product of the I₂ and I^– chemisorption in acid solutions is adsorbed iodine atoms. However, adsorption of iodine occurs in noticeable amounts and above a monolayer in the form of species that undergo electrodesorption during a cathodic polarization to potentials of the beginning of hydrogen adsorption. In the presence of a monolayer of adsorbed iodine atoms, potential of the zero total charge of a Pt/Pt electrode is in the oxygen adsorption region.     

[H3tren] templated iron fluorides; synthesis, crystal structures and Mössbauer studies

The hydrothermal synthesis, using tris-(2-ethylamino)amine (tren) as a template, and the crystal structures of three new hybrid iron fluorides, (H₃O)₂·[H₃tren]₂·(FeF₆)₂·(FeF₅(H₂O))·2H₂O (I), [H₃tren]₂·(FeF₆)₂·(FeF₂(H₂O)₄)·8H₂O (II) and [H₃tren]₂·(FeF₆)·(F)₃·H₂O (III), are reported. I, II, and III are triclinic (P-1), monoclinic (P2₁/c) and orthorhombic (I222), respectively. The structure of I is built up from isolated FeF₆ and FeF₅(H₂O) distorted octahedra separated by triprotonated [H₃tren]³⁺ cations, disordered H₃O⁺ cations and H₂O molecules. In II, Fe^IIIF₆ and neutral [Fe^IIF₂(H₂O)₄] octahedra form, together with [H₃tren]³⁺ cations, infinite (100) layers separated by extra water molecules. The structure of III consists of isolated and disordered FeF₆ octahedra, fluoride anions F⁻ connected to [H₃tren]³⁺ cations and extra fluoride anions F⁻ disordered with H₂O molecules. All [H₃tren]³⁺ cations have a “spider” type conformation. ⁵⁷Fe Mössbauer characterization shows that +III valence state can only be considered for iron cations in I and III and preliminary Mössbauer results are consistent with the presence of both +II and +III valences for iron cations in II, in agreement with the crystallographic results.     

Molecular structure of some [1.1 ]ferrocenylruthenocenophanium (n = 1,2 polyiodides salts

Oxidation of [1.1]ferrocenylruthenocenophane with a large excess and 1.5 equivalents of iodine gives dicationic iodo[1.1]ferrocenylruthenocenophanium²⁺I₃⁻ · 0.5I₂2 (1) and monocationic [1.1]ferrocenylruthenocenophanium⁺I₃⁻ (2) salts respectively. The structures of 1 and 2 were analyzed by single-crystal X-ray diffraction studies. The crystal form of 1 is monoclinic space group C2/c, A = 21.35](5), B = 20.594(5), C = 17.397(4) Å, β = 124.17(1)°, Z = 8, and the final R = 0.068 and R_w = 0.070. The cation formulated as [Fe^III(C₅H₄CH₂C₅H₄)₂Ru^IVI]²⁺ exists in a syn-conformation as in the cases of the neutral compound. The distance between the Ru^IV and Fe^II is 4.656(4) Å, which is much shorter than the value of the neutral compound (4.792(2) Å), and the bond angle of I---Ru^IV,Fe^III is 81.26°. The dihedral angle between the two η⁵-C₅H₄ (fulvenide) rings on the Ru^IV moiety is 37.56° due to the Ru^IV---I bond (2.758(3) Å). These two rings of Fe^III and Ru^IV moieties are essentially eclipsed. The unit cell has three kinds of I₃⁻ (I_3a⁻, I_3b⁻ and I_3c⁻) and one I₂, and the formula of 1 is given as [Fe^III(C₅H₄CH₂CSH₄)₂Ru^IVI]²⁺I₃⁻ · 0.5(I₃⁻)₂ · 0.5I₂. The crystal of 2 formulated as [Fe^III(C₅H₄CH₂C₅H₄)₂Ru^II]⁺I₃⁻ is triclinic space group

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, and the final R = 0.067 and R_w = 0.068. The unit cell has two independent molecules (unit A and B); i.e. two kinds of distance between the Ru^II and Fe^III, are observed; one (A) is 4.615(3) and the other (B) is 4.647(3) α. The two η⁵-C₅H₄ rings of both Fe^III and Ru^II are essentially staggered and the dihedral angles between the rings of FcH and RcH moieties are less than 5.8°. Typical ferrocenium-type broad singlet ⁵⁷Fe-Mössbauer lines are observed for both salts (1, 2) at all temperatures.     

Specific adsorption of iodide-ion at liquid (Ga-In)-electrode of eutectic composition from aqueous solutions with constant ionic strength

The adsorption behavior of iodide-ion at liquid (Ga-In)-electrode in aqueous electrolyte solutions at 305 K is studied by the electrochemical impedance spectroscopy, differential capacitance, and cyclic voltammetry. The equivalent circuit describing the experimental data in the presence and in the absence of the I⁻ ion is a series connection of a resistance and a capacitance that is frequency-independent over a ∼500 Hz to 100 kHz range. The experimental data were obtained by the mixed electrolyte method in electrolyte solutions acidified with HClO₄ down to pH 3, with excess of surface-inactive ion ClO₄⁻ and constant ionic strength (0.1 M). The analysis resulted in the determination of the charge σ₁ of the I⁻ ion specifically adsorbed at the liquid (Ga-In)-electrode at the adsorbate maximal concentration: σ_I = 7.73 μC/cm² in the case of analysis at σ = const (at the zero charge potential) or σ_I = 7.50 μC/cm² in the case of analysis at E = const. These values are characteristic of rather strong specific adsorption. The values of σ_I of the studied anion were used in the calculations of different isotherms with the purpose of the adsorption parameters determination. The obtained results were compared with literature data determined on other metals in the presence of specifically adsorbable I⁻ ion.     

The effect of the amphiprotic nature of human hair keratin on the adsorption of high charge density cationic polyelectrolytes

Adsorption of the cationic polymers poly(methacrylamidopropyltrimethyl ammonium chloride) (PMAPTAC) and poly(1,1-dimethylpiperidinium-3,5-diallylmethylene chloride) (PDMPDAMC) on human hair was studied by measurements of the amount of polymer adsorbed and by the streaming potential method. Results reflect the amphoteric nature of the keratin surface and show that the excess of anionic sites at pH values above 4 is the main driving force for the adsorption of cationic polyelectrolytes. Lowering the pH below 4 or addition of neutral salt (KCl) reduces the amount of adsorbed polymer. It was shown that the adsorption of cationic polymer in the concentration range 0.01 to 0.1 % and at neutral pH reverses the overall character of the surface from anionic to cationic. Keratin fibers modified in this manner do not exhibit amphoteric character and bear excess positive charge in the pH range 2–9.5. The value of the amount of the polymer adsorbed at saturation concentration (2 mg/g) as well as the lack of molecular weight effect in the range (5 · 10⁴ – 10⁶) on the amount of polymer adsorbed suggest that polymer chains adopt a rather extended conformation on the fiber surface. Some data concerning the formation of a complex between adsorbed cationic polymer and anionic detergents or polyelectrolytes are also presented.     

Voltammetry of immobilized cytochrome c on novel binary self-assembled monolayers of thioctic acid and thioctic amide modified gold electrodes

Horse heart cytochrome c (cyt c) was adsorbed on the binary self-assembled monolayers (SAMs) composed of thioctic acid (T-COOH) and thioctic amide (T-NH₂) at gold electrodes via electrostatic interaction. The cyt c adsorbed on the modified gold electrode exhibited well-defined reversible electrochemical behavior in 10 mM phosphate buffer solution (PBS, pH 7.0). The surface concentration (Γ) of electroactive species, cyt c, on the binary SAMs was higher than that in single-component SAMs of T-COOH, and reached a maximum value of 9.2 × 10⁻¹² mol cm⁻² when the ratio of T-COOH to T-NH₂ in adsorption solution was of 3:2, and the formal potential (E^0′=(E_pa+E_pc)/2) of cyt c was −0.032 V (vs. Ag|AgCl (3 M NaCl)) in a 10 mM PBS. The interaction between cyt c and the binary SAMs made the E^0′ shift negatively when compared with that of cyt c in solution (+0.258 V vs. NHE, i.e., +0.058 V vs. Ag|AgCl (3 M NaCl)). The fractional coverage of bound cyt c was a 0.64 theoretical monolayer. The standard electron transfer rate constant of cyt c immobilized on the binary SAMs was also higher than that on single-component SAMs of T-COOH, and the maximum value of 15.8 ± 0.6 s⁻¹ was obtained when the ratio of T-COOH to T-NH₂ in adsorption solution was at 3:2. The results suggest that the electrode modified with the binary SAMs functions better than the electrode modified with single-component SAMs of T-COOH.     

Transition metal complexes with thiosemicarbazide-based ligands. Part 56. Square-pyramidal complexes of copper(II) with 2-acetylpyridine S-methylisothiosemicarbazone

The article describes the synthesis and single-crystal X-ray analysis of two sulfato and one thiocyanato copper(II) complex with 2-acetylpyridine S-methylisothiosemicarbazone (HL) of the formulae [Cu(HL)SO₄(H₂O)]·H₂O (1), [Cu₂(HL)₂(μ-SO₄)₂]·2H₂O (2) and [Cu(HL)(NCS)(SCN)] (3), as well as the structure of the protonated ligand H₂L⁺I⁻. Complexes 1 and 2 were obtained from the reaction of aqueous/methanolic CuSO₄·5H₂O and ethanolic/methanolic H₂L⁺I⁻ solutions, respectively. Complex 3 was synthesized by the reaction of methanolic solutions of Cu(ClO₄)₂·6H₂O, the ligand and NH₄SCN, with the addition of triethyl orthoformate. All three complexes have a slightly deformed square-pyramidal structure (τ_av = 0.15) with the tridentate NNN neutral ligand in the basal plane. In complexes 1 and 3 the apical position is occupied by the oxygen atom of the monodentate SO₄ group, or the sulfur atom of the SCN group. Thanks to the hydrogen bonds, complex 3 may be thought of as having a pseudo-dimeric structure. In the authentic centrosymmetric dimer 2, the oxygen atoms of both SO₄ groups occupy also the apical position of both coordination polyhedra, as well as an equatorial position. Complexes 1 and 3 have μ_eff values characteristic of magnetically isolated mononuclear Cu(II) complexes. In contrast to them, complex 2 has a μ_eff value of 1.57 BM, which is in agreement with its dinuclear structure. All the complexes, in addition to the X-ray analysis and magnetic measurements, were characterized by IR and UV–Vis spectroscopy and by thermal analysis.     

Direct electrochemistry of recombinant tobacco peroxidase on gold

Direct electron transfer (DET) reactions of recombinant tobacco peroxidase (rTOP), namely direct electroreduction of Compound I/Compound II and heme Fe^3+/2+ conversion, were studied on gold electrodes. rTOP of wild type, non-glycosylated, was produced using an Escherichia coli expression system. At pH 5.0, the redox potential for direct electrochemical transformation of the Fe^3+/2+ of the peroxidase heme was −143 mV vs. AgAgCl, and 0.26 ± 0.07 pmol of the adsorbed rTOP were in DET contact with the gold electrode. The total amount of the adsorbed rTOP estimated from QCM data was 53 ± 5 pmol/cm² or 1.67 pmol when referred to the surface area of the electrodes used for electrochemical measurements. Of 1.67 pmol of adsorbed rTOP, only 0.76 pmol were catalytically active. DET between Au and the enzyme was also studied in the reaction of the bioelectrocatalytic reduction of H₂O₂ by cyclic voltammetry and amperometric detection of H₂O₂ at +50 mV with rTOP-modified Au electrodes placed in a wall-jet flow-through electrochemical cell. Maximal bioelectrocatalytic current response of the rTOP-modified gold electrodes to H₂O₂ was observed at pH 5.0 and stemmed from its bioelectrocatalytic reduction based on DET between Au and the active site of rTOP. Kinetic analysis of the DET reactions gave 52% of the adsorbed rTOP molecules active in DET reactions (0.4 pmol of adsorbed catalytically active rTOP, correspondingly), which correlated well with the non-catalytic-voltammetry data. DET was characterised by a heterogeneous ET rate constant of 13.2 s⁻¹, if one takes into account the QCM data, and 19.6 s⁻¹, if the amount of rTOP estimated from the data on DET transformation of Fe^3+/2+ couple of rTOP is considered. The sensitivity for H₂O₂ obtained for the rTOP-modified Au electrodes was 0.7 ± 0.1 A M⁻¹ cm⁻². These are the first ever-reported data on DET reactions of anionic plant peroxidases on bare gold electrodes.     

Crystal Structure and Thermal Decomposition of 5-Aminotetrazole Trinitrophloroglucinolate

5-Aminotetrazole trinitrophloroglucinolate ((ATZ)TNPG) was prepared and characterized by elemental analysis and FT-IR spectroscopy. The crystal structure was determined by X-ray diffraction analysis and it belonged to orthorhombic system and Pbca space group with a=0.6624(2) nm, b=1.7933(4) nm, c=2.3117(5) nm, V=2.7458(9) nm³, Z=4, and D_c=1.849 g·cm⁻³. The molecular formula was confirmed to be (ATZ)TNPG·2H₂O. 5-Aminotetrazole cation (ATZ⁺) and trinitrophloroglucinol anion (TNPG⁻) were linked into 2-D layers along b-axis and c-axis by hydrogen bonds. Then the layers were linked along a-axis by hydrogen bonds between the water molecules belonging to different layers. The thermal decomposition mechanism of the compound was studied by differential scanning calorimetry (DSC), thermogravimetry-thermogravimetric analysis (TG-DTG), and Fourier transform-infrared (FT-IR) spectroscopy techniques. Under nitrogen atmosphere with a heating rate of 10 °C·min⁻¹, the compound experienced one endothermic process with peak temperature of 76 °C and one exothermal process with peak temperature of 203 °C. The former was confirmed to be a dehydrate process. The latter was the decomposition of TNPG⁻ and ATZ⁺ in the compound. The exothermic enthalpy change of this process was −212.10 kJ·mol⁻¹. The kinetic parameter calculation from Kissinger's method were, E=132.1 kJ·mol⁻¹, ln(A/s⁻¹)=12.54 with r=0.9990, and the calculation results from Ozawa-Doyle's method were, E=133.1 kJ·mol⁻¹ with r=0.9992.     

The d metal-sulfosalicylate complexes: Herring-bone, ladder and double-stranded chain frameworks with green luminescences

Assembly of 5-sulfosalicylic acid (H₃L) and d¹⁰ transition metal ions (Cd^II, Ag^I) with the neutral N-donor ligands produces five new complexes: [Cd₂(HL)₂(4,4′-bipy)₃]_n·2nH₂O (1), {[Cd₂(μ₂-HCO₂)₂(4,4′-bipy)₂(H₂O)₄][Cd(HL)₂(4,4′-bipy)(H₂O)₂]}_n (2), {[Cd(4,4′-bipy)(H₂O)₄][HL]·H₂O}_n (3), [Cd(HL)(dpp)₂(H₂O)]_n·4nH₂O (4), {[Ag(4,4′-bipy)][Hhbs]}_n (5) (4,4′-bipy=4,4′-bipyridine, dpp=1,3-di(pyridin-4-yl)propane, H₂hbs=4-hydroxybenzenesulfonic acid, the decarboxylation product of H₃L). Complex 1 adopts a 5-connected 3D bilayer topology. Complex 2 has the herring-bone and ladder chain, which are extended to a 3D network via hydrogen bonding. In 3–4 complexes, 3 is a 3D supermolecular structure formed by polymeric chains and 2D network of HL²⁻, while 4 gives the double-stranded chains. In 5, ladder arrays are stacked with the 2D networks of Hhbs⁻ anions in an –ABAB– sequence. Complexes 1–4 display green luminescences in solid state at room temperature, while emission spectra of 3 and 4 show obvious blue-shifts at low temperature.     

Adsorption of<Emphasis Type="Italic"> N</Emphasis>-dodecyl-<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-dimethyl-3-ammonio-1-propanesulfonate (DDAPS), a model zwitterionic surfactant,on the Au(111) electrode surface

Electrochemical measurements including cyclic voltammetry, differential capacity, and chronocoulometry have been used to characterize the adsorption behaviors of the zwitterionic surfactant N-dodecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (DDAPS) on the Au(111) electrode surface. The thermodynamics of the ideally polarized electrode have been employed to determine the Gibbs excess and the Gibbs energy of adsorption. The results show that the adsorption of DDAPS has a multistate character. The first two states are observed at potentials close to zero charge. At low bulk DDAPS concentrations, it corresponds to the formation of a film of nearly flat adsorbed molecules. At higher concentrations it is converted into a hemimicellar state. The second state is formed at negative potentials and charge densities close to 0 C cm^–2. It corresponds to a film of tilted molecules oriented with the hydrocarbon tail towards the metal and the polar head toward the solution.Dedicated to Professor Zbigniew Galus on the occasion of his 70^th birthday and in recognition of his many contributions to electrochemistry.     

Synthesis and structure determination of a novel lithium copper vanadate LiCu2VO4(OH)2

A novel lithium copper vanadate LiCu₂VO₄(OH)₂ (I) and Volborthite Cu₃V₂O₇(OH)₂ are two phases obtained at 170 °C by hydrothermal synthesis during the study of the CuO; V₂O₅; Li₂O; H₂O system. Compound (I) crystallizes in the orthorhombic system, with the space group P2₁2₁2₁ (No. 19) and with the unit-cell parameters a=9.6086(2) Å, b=8.4482(2) Å, c=5.8938(1) Å. The structure was determined from powder by an “ab initio” method using the EXPO software and refined with GSAS, a Rietveld refinement package. Wave-like layers of rutile-type copper chains sharing vertex with the neighbor chains, are linked into a three-dimensional framework by rows of alternating tetrahedra of vanadium and trigonal bipyramids of lithium which share edges and vertices with the copper octahedra.     

Crystal chemistry of three new monodimensional fluorometalates templated with ethylenediamine

Three new monodimensional hybrid metal (Ti, In, Al) fluorides are synthesized with ethylenediamine (en) as a templating agent in solvothermal conditions assisted by microwave heating. All structures involve inorganic chains built up from TiO₂F₄ octahedra connected by two opposite O²⁻ vertices in [H₂en]·(TiOF₄) (I), from InF₆(H₂O) pentagonal bipyramids linked by F–F edges in [H₂en]·(InF₄(H₂O))₂·H₂O (II) and from (Al₇F₃₀)⁹⁻ polyanions sharing two opposite AlF₆ octahedra in [H₂en]₃·(Al₆F₂₄) (III). I is tetragonal, P4/ncc, a = 12.761(3) Å, c = 8.041(3) Å; II is orthorhombic, F2dd, a = 6.904(5) Å, b = 16.559(5) Å, c = 19.777(4) Å and III is monoclinic, P2₁/n, a = 9.387(2) Å, b = 6.710(2) Å, c = 21.513(6) Å, β = 97.18(3)°.     

Dinitrogen and carbon monoxide hydrogen bonding in protonic zeolites: Studies from variable-temperature infrared spectroscopy

Adsorption (at a low temperature) of nitrogen on the protonic zeolite H-Y results in hydrogen bonding of the adsorbed N₂ molecules with the zeolite Si(OH)Al Brønsted-acid groups. This hydrogen-bonding interaction leads to activation, in the infrared, of the fundamental N–N stretching mode, which appears at 2334 cm⁻¹. From infrared spectra taken over a temperature range, the standard enthalpy of formation of the OH···N₂ complex was found to be ΔH⁰ = −15.7(±1) kJ mol⁻¹. Similarly, variable-temperature infrared spectroscopy was used to determine the standard enthalpy change involved in formation of H-bonded CO complexes for CO adsorbed on the zeolites H-ZSM-5 and H-FER; the corresponding values of ΔH⁰ were found to be −29.4(±1) and −28.4(±1) kJ mol⁻¹, respectively. The whole set of results was analysed in the context of other relevant data available in the literature.