An electron spin resonance (ESR) and simultaneous electrochemical and electron spin resonance (SEESR) spectroscopic study of motion, stability and potential controlled release of radical guests from the β-cyclodextrin inclusion polymer

The influence of molecular inclusion and separation of radical guests inside the amorphous β-cyclodextrin host polymer (β-CDP) matrices on the motion and stability as well as controlled potential release of radicals was studied by electron spin resonance spectroscopy (ESR) and simultaneous electrochemistry and electron spin resonance (SEESR) spectroscopy. A pronounced restriction of rotational motion was observed for the included stable protonated form of the 4-amino-2,2,6,6-tetramethylpiperidine-1-oxyl (4-amino-TEMPO) free radical and a partial restriction of motion of the NN,N',N'-tetramethyl-1,4-phenylenediamine (TMPD^.+) radical (generated ex situ by controlled potential electrolysis), while virtually no restriction was found in the case of the methyl (MV^.+) and heptyl viologen (HV^.+) monocation radicals as well as of the 2-nitrotoluene anion radical (2NT^.− ). The MV^.+, HV^.+ and 2NT^.− unstable radicals were electrochemically generated inside the β-CDP film coat at a Pt flag electrode. The rate of the open-circuit decay of the included unstable radicals was markedly decreased as compared with their decay at the bare electrode. It was also found that the extent of inclusion of alkyl viologens was governed by their ionic charge, i.e. the higher the charge of the ion the weaker its inclusion.     

Struktur‐Eigenschafts‐Beziehung von Cu5Pb6O3Cl11, einer gut Kupferionen leitenden Verbindung

Structure‐Behaviour‐Relation of Cu₅Pb₆O₃Cl₁₁, a Good Solid State Ionic Conductor for Cu⁺‐Ions A new compound within the group of coin metal lead(II) oxide halides is found and characterized by X‐ray single crystal structure determination in a temperature range from 120 K to 400 K. Cu₅Pb₆O₃Cl₁₁ shows a new crystal type structure with a = 21.098(4) Å, b = 10.233(2) Å, c = 12.224(2) Å, β = 124.08(3)°, Z = 4 and space group C 2/c (No. 15) at 120 K. There are found isolated oxidic chains built of OPb₄ tetrahedra beside columnar areas consisting of CuCl. In this halidic partial structure are a lot of empty and partially occupied Cl₄‐tetrahedra. This structural characteristic seems to be source of a very good conductivity of copper ions, like in microscopic and nanoscaled composites of Al₂O₃ and AgI.     

A methodology for the determination of reductive sulphur in optical and technical glass

This paper describes an analytical method for the determination of reductive sulphur (S(IV), S(-II)) in glass. The glass sample is dissolved in hydrofluoric/hydrochloric acid mixture and the sulphur is separated via distillation in an apparatus made of polyfluoralkoxyethylene (PFA). The distilled hydrogen sulphide is trapped in buffered boric acid-zinc acetate solution and subsequently determined after conversion to an ethylene blue dye. The range of the method lies within a range of 2-1200 μg g⁻¹ reductive sulphur. The quantification limit for reductive sulphur is 2 μg g⁻¹.Different analysed glass types show either no detectable reductive sulphur or up to 30% of the total sulphur content reductive sulphur. The inter-laboratory standard deviation shown by a round robin test performed is excellent (±4 μg g⁻¹; average 59 μg g⁻¹). Sources of error of the methodology are discussed.     

Synthese,Kristallstruktur und thermische Entwässerung von CsMnF4 · 2H2O

Synthesis, crystal structure and thermal dehydration of CsMnF₄ · 2H₂O The preparation of a new fluoromanganate (III)-complex CsMnF₄ · 2H₂O is reported. It crystallizes in the monoclinic space group C2 with a = 11.891(2) Å, b = 6.589(1) Å, c = 10.558(1) Å, β = 131.46(1)° and Z = 4. The crystal structure has been solved from diffractometer data by heavy-atom methods and refined to a conventional R-value of 1.8% (including the contributions of three hydrogen atoms in measured and one in calculated positions). The structure is characterized by isolated, tetragonally distorted [MnF₄(OH₂)₂]-octahedra with Mn-F-distances from 1.801(8) Å to 1.870(7) Å and Mn-O-distances of 2.146(6) Å and 2.268(6) Å. Cesium exhibits an irregular 10-coordination by 8 F-atoms and 2 O-atoms (mean values for the two independent cesium ions: Cs-F = 3.17 Å and 3.21 Å, Cs-O = 3.32 Å and 3.29 Å). The [MnF₄(OH₂)₂]-octahedra are connected to six neighbouring octahedra by hydrogen bonding. The dehydration of the complex has been studied by thermoanalytical methods and power x-ray-diffractometry. The unit cell of the dehydrated compound, CsMnF₄, is tetragonal with a = 7.936(1) Å and c = 6.341(1) Å. A close relationship to the structure of CsFeF₄, which is a superstructure variant of the T1A1F₄-type[6], is indicated by the similarity of the corresponding unit cells and preliminary structure factor calculations. A proposition for the crystal structure of CsMnF₄ is developed on the basis of (2 + 2 + 2)-orthorhombic distorted MnF₆-octahedra.     

Application of sustained off-resonance irradiation infrared multiphoton dissociation tandem mass spectrometry to the analysis of biomolecules

A modified pulse sequence for infrared multiphoton dissociation (IRMPD) experiments on a Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer in conjunction with sidekick trapping is presented. For IRMPD tandem mass spectrometry experiments gated trapping is normally applied. It ensures that the ions remain on-axis and, thus, cross the laser beam which is aligned on-axis in commercially available instruments. Sidekick trapping is used to capture more ions in the ICR cell in order to increase the signal intensity. However, it may lead to off-axis ion motion, which reduces or even excludes interaction with the laser beam. In this contribution sustained off-resonance irradiation (SORI) was applied to overcome this disadvantage of sidekick trapping. SORI is normally used in conjunction with collision-induced dissociation (CID) experiments to increase the kinetic energy of the ions. Here, SORI is used to influence the cyclotron motion during the laser irradiation time, which leads to temporary intersection of the ion trajectory with the laser beam. With this easy-to-handle experimental setup, IRMPD of ions captured with sidekick trapping leads again to the generation of fragment ions as is demonstrated with several biologically relevant samples like peptides, lipids and glycolipids.     

Benetzungswärmen dotierter Festkörper

Summary Heats of immersion have been measured by the method ofStowe with butyl derivatives of different dipol moments as liquids and with doped semiconductingp- andn-alumina, ion charged zeolithes and with cracking catalysts as solids. The heat of immersion is proportional to the dipol moment of the liquid and can be used as measure of the polarity of the surface. In doped aluminas it has a maximum in the undoped (intrinsic) samples, which shows that a dope whatsoever removes dipols from the surface. In zeolithes substitution of sodium by divalent cations leads to a decrease of the immersion heat, parallel to the activation energy of the cumene cracking. The effect is interpreted by cross linking and hence closing of pores for butyl compounds and cumene. This is confirmed by the absence of the effect with the smaller molecule of methanol.

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Vorgetragen auf dem XX. IUPAC-Kongre\, Moskau 1965.

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Dem Fond der Chemischen Industrie und der Deutschen Forschungsgemeinschaft haben wir für Unterstützung der Untersuchung zu danken.     

Lipophilic salts as membrane additives and their influence on the properties of macro- and micro-electrodes based on neutral carriers

The influence of salts containing lipophilic cations and anions on the electrical resistance of the membranes of calcium ion-selective macro- and micro-electrodes based on a neutral carrier is described. The resistance of macroelectrodes was decreased by a factor of about 50 or of about 3 compared to membranes without and with potassium tetrakis- (p-chlorophenyl)borate, respectively. No significant reduction of the membrane resistance was achieved for microelectrodes. The lower detection limit and the Ca²⁺/K⁺ selectivity factor were improved for both types of electrode.     

Analytical performance characteristics of thin and thick film amperometric microcells

The analytical performance of amperometric microcells with different electrode geometries is compared for enzyme activity measurements. The microcells were fabricated with thin film photolithography or thick film screen-printing in four different designs. The cells made with the thin film process used flexible substrate with microelectrode array or a circular, disk-shaped working electrode. The screen-printed working electrodes had semicircle or disk shape on ceramic chips. Putrescine oxidase (PUO) activity measurement was used as a model. The determination of PUO activity is important in the clinical diagnosis of premature rupture of the amniotic membrane. An electropolymerized m-phenylenediamine size-exclusion layer was used to eliminate common interferences. The size exclusion layer revealed also to be advantageous in protecting the electrodes from fouling by putrescine (enzyme substrate). The electrode fouling of bare electrodes was insignificant for screen-printed electrodes, but very severe for electroplated platinum working electrodes. The microelectrode array electrodes demonstrated smaller RSD and higher normalized sensitivities for hydrogen peroxide and PUO activity. All the other electrodes were demonstrating comparable analytical performances.     

Structure of de-o-acylated lipopolysaccharide from the escherichia coli re mutant strain F 515

The structure of the oligosaccharide portion of an $\text{E.coli}$ Re lipopolysaccharide was determined as α-KDO-(2→4)-α-KDO-(2→6)-β-GlcN-α(1→6)-α-GlcN, bisphosphorylated at positions 1 and 4′. Taking into account the previous determination of the acylation pattern of the GlcN disaccharide, the total structure of $\text{E.coli}$ Re LPS was thus established.