How it All Started at DESY in 1964

To put it bluntly, synchrotrons and storage rings were originally not intended to become light sources for synchrotron radiation (SR). If particle physicists had not driven this development for their own needs, we would not yet have these sources available at their present level of sophistication. In 1964, when the then-6 GeV synchrotron DESY at the newly founded Hamburg institution of the same name started operating, SR was considered at best a nuisance. Accelerating an electron to 6 GeV was accompanied by a loss of 9.35 GeV on its way due to this radiation, and later, at 7.5 GeV, the loss amounted to 22.8 GeV. How could it then happen that today all of the DESY storage rings and linear accelerators are devoted to SR?     

Synthesis,molecular structure and reactivity of the dimethyl sulfide adduct of a 1,3,2-diselenaborolane with an annelated dicarba-closo-dodecaborane(12) unit

The reaction of 1,2-diselenolato-1,2-dicarba-closo-dodecaborane(12) dianion [1,2-(1,2-C₂B₁₀H₁₀)Se₂]²⁻ with HBBr₂–SMe₂ affords the dimethyl sulfide adduct of 4,5-[1,2-dicarba-closo-dodecaborano(12)]-1,3-diselena-2-borolane in good yield. The molecular structure was determined by X-ray diffraction, and the solution-state structure was established by NMR spectroscopy (¹H, ¹¹B, ¹³C, ⁷⁷Se NMR). ¹¹B and ⁷⁷Se chemical shifts were reproduced by DFT calculations. Attempts were made to abstract dimethyl sulfide, and the parent donor-free compound could be detected in solution. The reactivity of the title compound was studied towards pyridine, Me₃SnF, [Pt(PPh₃)₂(C₂H₄)], tert-Bu-OH, AlMe₃ and AlH₃-N(Et)Me₂ as well as a hydroborating reagent.     

Characterization of polyoxyalkylene block copolymers by combination of different chromatographic techniques and MALDI-TOF-MS

Polyoxyalkylene diblock copolymers (consisting of PEO as hydrophilic block and PBO or PHO as hydrophobic block) are characterized by combination of two dimensional liquid chromatography and MALDI-TOF-MS. Liquid chromatography under critical conditions (LCCC) is used as first dimension and fractions are collected, mobile phase evaporated and diluted in the mobile phase used in the second dimension (SEC, LCCC or LAC). This two-dimensional chromatography in combination of MALDI-TOF-MS gives information about purity of reaction products, presence of the byproducts, chemical composition and molar mass distribution of all the products.     

A Versatile Method for Quantification of Aflatoxins and Ochratoxin A in Dried Figs

JPC – Journal of Planar Chromatography – Modern TLC - Thin-layer chromatography is a rapid and reliable working method for quantification of mycotoxins which is suitable for checking EC...     

A Selective Ru‐Catalyzed Semireduction of Alkynes to Z Olefins under Transfer‐Hydrogenation Conditions

By using a readily available, air‐ and moisture‐stable dihydrido–Ru complex, a variety of Z olefins are accessible under transfer‐hydrogenation conditions with formic acid as the hydrogen source in excellent yields and Z/E selectivities.     

Tungsten(VI) and Tungsten(V) Fluoride Complexes

WF₆ reacts with phosphines R₃P forming 1:1 compounds. With R=P(CH₃)₃ the coordination around the tungsten atom is capped trigonal prismatic, with R=P(CH₃)₂C₆H₅ the coordination is capped octahedral, as established by single‐crystal structure determinations: [(CH₃)₃P? WF₆]: a=752.5(21), b=945.7(24), c=629.8(18) pm. β=110.36(13)°, space group Cm, Z=2; [(CH₃)₂(C₆H₅)P? WF₆]: a=762.2(2), b=1123.5(2), c=2647.5(6) pm, space group Pbca, Z=8. [(CF₃CH₂)₂N? WF₅] reacts smoothly with P(C₆H₅)₃ forming known P(C₆H₅)₃(F)₂ and [(CF₃CH₂)₂N? WF₄? P(C₆H₅)₃], a stable, green, molecular species, identified among other methods with an crystal structure determination: a=914.9(1), b=956.0(1), c=1449.8(2) pm, α=7.642(4), β=81.648(3), γ=81.519°, space group P$\bar 1$ , Z=2.     

Ion‐Pair Complexation with a Cavitand Receptor

The capability of resorcinarenes to bind anions within the alkyl feet at the lower rim has been exploited as the starting point for developing a new cavitand able to engulf contact ion pairs of primary ammonium salts in chlorinated solvents with association constants (K_ass) in the range of 10³–10⁴ M ^?1. Methylene bridges were introduced into the upper rim to freeze the resorcinarene in the cone conformation with the four H_down protons converging in the lower pocket, thereby maximizing the CH–anion interactions responsible for the anion binding. Four additional phosphate moieties were introduced into the lower rim in close proximity to the anionic site to provide hydrogen‐bonding‐acceptor P?O groups and promote cation complexation at the bottom of the cavitand. The binding ability of the synthesized ligands was analyzed by ¹H NMR spectroscopy and, when possible, by isothermal titration calorimetry (ITC); the data were in agreement when complementary techniques were used.     

Interplay of Magnetic Exchange Interactions and Ni?S?Ni Bond Angles in Polynuclear Nickel(II) Complexes

The ability of bridging thiophenolate groups (RS^?) to transmit magnetic exchange interactions between paramagnetic Ni^II ions is examined. Specific attention is paid to complexes with large Ni? SR? Ni angles. For this purpose, dinuclear [Ni₂L¹(μ‐OAc)?I₂][I₅] ( 2 ) and trinuclear [Ni₃L²(OAc)₂][BPh₄]₂ ( 3 ), where H₂L¹ and H₂L² represent 24‐membered macrocyclic amino‐thiophenol ligands, are prepared and fully characterized by IR‐ and UV/Vis spectroscopy, X‐ray crystallography, static magnetization M measurements and high‐field electron spin resonance (HF‐ESR). The dinuclear complex 2 has a central N₃Ni₂(μ‐S)₂(μ‐OAc)Ni₂N₃ core with a mean Ni? S? Ni angle of 92°. The macrocycle L² supports a trinuclear complex 3 , with distorted octahedral N₂O₂S₂ and N₂O₃S coordination environments for one central and two terminal Ni^II ions, respectively. The Ni? S? Ni angles are at 132.8° and 133.5°. We find that the variation of the bond angles has a very strong impact on the magnetic properties of the Ni complexes. In the case of the Ni₂‐complex, temperature T and magnetic field B dependencies of M reveal a ferromagnetic coupling J=?29 cm^?1 between two Ni^II ions (H=JS₁S₂). HF‐ESR measurements yield a negative axial magnetic anisotropy (D<0) which implies a bistable (easy axis) magnetic ground state. In contrast, for the Ni₃‐complex we find an appreciable antiferromagnetic coupling J′=97 cm^?1 between the Ni^II ions and a positive axial magnetic anisotropy (D>0) which implies an easy plane situation.     

Retention of functional polymers in liquid adsorption chromatography: Effect of the end groups in PEGs and their methyl ethers in different mobile phases

It is shown that the end group parameter, which describes the influence of the end group on retention, can be determined in RP chromatography from two chromatograms of a nonfunctional and a monofunctional sample, if a sufficient number of peaks with the same number of repeat units in each sample can be reasonably resolved and identified. The same procedure can also be applied for pairs of di‐ and monofunctional polymers. End group parameters have been determined in three different mobile phases: acetonitrile–water, acetone–water and methanol–water of different compositions. The temperature dependence of the interaction parameter of the repeat unit and the end group parameter has been found to be different, which allows a fine‐tuning of retention.