Systematic Study of the Interaction Between VIV Centres and LnIII Ions in Well Defined {V 2 IV LnIII}{AsIIIW9O33}2 Sandwich-Type Clusters: Part 2

The gadolinium (Gd) member of a new type of heteropolytungstates that contain one lanthanide and two transition metal ions in a triangular arrangement is reported. The compound NaK₆Gd_0.33 [((VO)₂Gd(H₂O)₄K₂(H₂O)₂(Na)(H₂O)₂)(α-B-AsW₉O₃₃)₂]·24H₂O (1) was prepared from acidified aqueous solutions of Na₂WO₄·2H₂O, As₂O₃ and VOSO₄·5H₂O to which Gd³⁺ ions were added. The single crystal X-ray structure analysis (monoclinic, space group P2₁/m) shows that the anion consists of two [α-B-As^IIIW₉O₃₃]^9? trilacunary Keggin-type units linked by two VO²⁺, one Gd³⁺ as well as weakly by two K⁺ and one Na⁺ ions, resulting in a sandwich-type structure with idealized C _2v symmetry. The problem of positioning crystal lattice and special polyoxometalate sites with different cations is discussed also in connection with supramolecular chemistry aspects and as an option for further research. A fit of the magnetic susceptibility yielded exchange coupling constants of J _VV = ?2.55 cm^?1 (anti-ferromagnetic) between the vanadium ions and J _GdV = 0.6 cm^?1 (ferromagnetic) between the Gd and each of the two vanadium ions. The complete magnetochemical analysis also revealed a partial occupancy of the Na⁺ sites in the counter-cation–water system by Gd³⁺ ions (0.33 Gd³⁺ ions in total).     

Hydridoorganostannylene Coordination: Group 4 Metallocene Dichloride Reduction in Reaction with Organodihydridostannate Anions

Organodihydridoelement anions of germanium and tin were reacted with metallocene dichlorides of Group 4 metals Ti, Zr and Hf. The germate anion [Ar*GeH₂]⁻ reacts with hafnocene dichloride under formation of the substitution product [Cp₂Hf(GeH₂Ar*)₂]. Reaction of the organodihydridostannate with metallocene dichlorides affords the reduction products [Cp₂M(SnHAr*)₂] (M=Ti, Zr, Hf). Abstraction of a hydride substituent from the titanium bis(hydridoorganostannylene) complex results in formation of cation [Cp₂M(SnAr*)(SnHAr*)]⁺ exhibiting a short Ti–Sn interaction. (Ar*=2,6-Trip₂C₆H₃, Trip=2,4,6-triisopropylphenyl).     

Application of displacement chromatography for the proteome analysis of a human plasma protein fraction

It was the aim of this study to compare the performance of displacement chromatography with gradient elution chromatography both applied as the cation-exchange separation step for a proteome analysis in a bottom-up approach using multidimensional chromatography for the separation of tryptic peptides prior to their mass spectrometric analysis. The tryptic digest of the human Cohn fraction IV-4 served as a sample. For both chromatography modes commonly used operating parameters were chosen thus ensuring optimal separation results of equal sample amounts for each mode. All resulting fractions were analyzed with an HPLC-chip–LC–MS system. The eluate of the HPLC-chip column was ionized by electrospray ionization (ESI) and analyzed with an ion-trap mass spectrometer. For guaranteeing high confidence concerning the identity of the peptides, the mass spectrometric data were processed by different bioinformatic tools applying stringent criteria. By the displacement approach the total amount of identified proteins (78) was significantly higher than in the gradient mode (58). The results showed that displacement chromatography is a well suited alternative in comparison to gradient elution separation for analysis of proteomes via the bottom-up approach applying multidimensional chromatography, especially in those cases when larger quantities of proteins are available.     

Fiber optic multi-channel protein detector for use in preparative continuous annular chromatography

On-line coupling continuous-flow liquid membrane extraction (CFLME) with HPLC, a novel automatic system was developed for the determination of sulfonylurea herbicides in water. After an automatic trace-enrichment process by CFLME, which is the combination of continuous flow liquid-liquid extraction and support liquid membrane (SLM) extraction, the target analytes were concentrated in 50 microl of 0.2 M Na2CO3-NaHCO3 (pH 10.0) buffer. The concentrated sample solutions were injected directly onto a C18 analytical column with a valve, and detected at 240 nm with a diode array detector. Metsulfuron methyl (MSM), and DPX-A 7881 were baseline separated with a mobile phase consisting of methanol and 67 mM KH2PO4-Na2HPO4 (pH 5.91) buffer (45+55, v+v) at a flow-rate of 1.0 ml min(-1). With an enrichment time of 10 min and enrichment sample volume of 20 ml, the enrichment factors and detection limits are 100 and 0.05 microg l(-1) for MSM, and 96 and 0.1 microg l(-1) for DPX-A 7881, respectively. The linear range and precision (RSD) are 0.1-50 microg l(-1) and 7.0% for MSM, and 0.2-50 microg l(-1) and 9.2% for DPX-A 7881, respectively. This proposed method was applied to determine MSM and DPX-A 7881 in seawater, tap water, and bottled mineral water with spiked recoveries in the range of 83-95% for MSM and 88-100% for DPX-A 7881, respectively.     

Novel Hyperbranched Poly([1,2,3]‐triazole)s Derived from AB2 Monomers by a 1,3‐Dipolar Cycloaddition

Summary: Novel hyperbranched poly([1,2,3]‐triazole)s were synthesized from several AB₂ monomers by a 1,3‐dipolar cycloaddition reaction. The compound 3,5‐bis(propargyloxy)benzyl azide was polymerized thermally at room temperature leading to 1,4‐ and 1,5‐disubstituted poly([1,2,3]‐triazole) and catalytically leading only to the 1,4‐disubstituted poly([1,2,3]‐triazole). Only the thermal reaction led to fully soluble products. The AB₂ monomers containing an internal alkyne A unit could be autopolymerized thermally under mild reaction conditions leading to soluble, high‐molecular‐weight hyperbranched poly([1,2,3] triazole)s. All products were characterized by detailed NMR investigations.

Synthesis route for polymers 8a and 8b .     

Hyperbranched thermolabile polycarbonates derived from a A2+B3 monomer system

Hyperbranched polycarbonates were synthesized successfully via the A₂ + B₃ route by the reaction of a bis(carbonylimidazolide) with triethanolamine. These polymers containing the carbonate group as thermolabile moiety are decomposing into volatile products at around 200°C. The polymers were characterized with ¹H/¹³C NMR spectroscopy, SEC, DSC and TGA techniques.     

Studying lateral diffusion in lipid bilayers by combining a magic angle spinning NMR probe with a microimaging gradient system

An alternative technique for studying the lateral diffusion in lipid membranes using pulsed field gradients in combination with magic angle spinning is presented. It is shown that MAS probes inserted in a microimaging device that produce high field gradients can be used to monitor also slow diffusion processes. As an example, measurements of the lateral diffusion of lipids embedded in the bilayer of a cubic phase are presented.     

Hydrogen Bonding in Pyridine N-Oxide/Acid Systems: Proton Transfer and Fine Details Revealed by FTIR, NMR, and X-ray Diffraction

The H-bonded complexes of pyridine N-oxide (PyO) with H(2)O, acetic, cyanoacetic, propiolic, tribromoacetic, trichloroacetic, trifluoroacetic, hydrochloric, and methanesulfonic acids have been studied by FTIR and NMR spectroscopy, X-ray diffraction, and quantum chemical DFT calculations. Correlations between vibrational frequencies of the NO stretching and PyO ring modes and geometric parameters of the H-bond have been established. FTIR experiments show and DFT calculations confirm that definite discontinuity is present in the vicinity of the midpoint in the proton transfer pathway. The established correlations significantly aid in the understanding of fine effects such as the isotope (deuteration) effect, crystal-to-solution transition, or criticality of aqueous solutions induced by ionic pairs. Geometric isotope effect in the ionic H-bond aggregate of PyO·H(D)Cl was found to be extraordinary large. Measured FTIR, CP/MAS, and high-resolution (13)C NMR spectra indicate that H-bond in the PyO·HCl complex in polar solvent can potentially be more ionic than in the crystal. Vibrational modes of ionic pairs originating via proton transfer in H-bond complexes can provide new information concerning the interionic interaction and its role in the phase separation and mezo-structuring processes. The results are compared to the relevant data for PyO·HCl complex in argon matrix.