Offset‐compensated and zero‐quantum suppressed ROESY provides accurate 1H–1H distances in small to medium‐sized molecules

A robust version of the off‐resonance ROESY pulse scheme is suggested for the measurement of proton–proton distances or slow chemical exchange in small to medium‐sized molecules. The method implements adiabatic ramps to establish a pair of opposite frequency off‐resonance spin lock fields – with optionally randomized duration – and adiabatic inversion pulses with simultaneous gradients for efficient zero‐quantum suppression. The amended pulse sequence yields pure absorption cross‐peaks and works safely for small to medium‐sized molecules. The applicability of the method has been demonstrated using small, rigid molecules (strychnine and codeine) and was also applied for a cyclic peptide and a small protein. We found that the pure phase cross‐peaks of the new ROESY version are beneficial for distance measurements. The one‐dimensional (selective) version of the new method is also powerful for measuring selected pair‐wise interactions and distance determination. Copyright © 2016 John Wiley & Sons, Ltd.     

Erd?s–Szekeres Theorem for Point Sets with Forbidden Subconfigurations

According to the Erd?s?CSzekeres theorem, every set of n points in the plane contains roughly logn points in convex position. We investigate how this bound changes if our point set does not contain a subset that belongs to a fixed order type.     

Ni diffusion in near-equiatomic Ni-Ti and Ni-Ti(-Cu) alloys

Tracer volume diffusion of 63 Ni in Ni-50.07 at.% Ti binary and Ni-48.83 at.% Ti-9.29 at.% Cu ternary alloys have been measured between 783 and 1288 K. The temperature dependence of the diffusion coefficients can be well described by a straight Arrhenius function This illustrates that a diffusional anomaly (typical in some bcc metallic alloys and related to the well-known phonon softening), if there is any in this system, is negligible. On the other hand, the small activation energy (about half the value expected from simulations for the commonly accepted mechanism with thermally activated vacancies) shows that the mechanism of diffusion is probably mediated by structural vacancies.     

Synthesis of a new compound family, 1-aryl-3H-pyrrolo[2,1-d][1,2,5]triazepin-4(5H)-ones

Representatives of a new family, 1-aryl-3H-pyrrolo[2,1-d][1,2,5]triazepin-4(5H)-ones have been synthesized at our laboratory as bioisosters of biologically active 1-aryl-2,3-benzodiazepine-4-ones. The efficient synthetic route described applies the synthesis of 2-(2-aroylpyrrol-1-yl)acyl hydrazides followed by ring closure under acidic conditions. The N(3)-unsubstituted title compounds thus obtained can optionally be N-alkylated rendering the preparation of variously substituted derivatives possible. Scope and limitations of the new protocol and some interesting side reactions are also discussed in detail.     

Efficient syntheses of the versatile phthalide building blocks, 5,6-diaminoisobenzofuran-1(3H)-one and 5H,7H-furo[3,4-f][2,1,3]benzothiadiazol-5-one

A new and efficient synthesis of 5,6-diaminophthalide and a novel thiadiazolophthalide has been accomplished. Both molecules are useful starting compounds for the construction of more complex heterocyclic systems and for the preparation of bioisosteres of methylenedioxyphenyl derivatives.     

Occurrence of antimony and phthalate esters in polyethylene terephthalate bottled drinking water

Interest in studying leaching of toxic (in)organic contaminants such as antimony (Sb) and phthalate esters into drinking water increased because of the ever growing market of water bottled in polyethylene terephthalate (PET) packaging material. Possible contamination sources of drinking water contained in PET bottles are hereby reviewed. Instrumental analytical methods suitable for Sb and phthalate ester determination in drinking water and PET material are also presented. Outcomes on leaching of Sb and phthalate esters into drinking water are grouped according to storage time, exposure to heat/light, sample pH, and PET bottle volume. Methods for estimation of toxicological activity of water in PET bottles are also compiled. Normally, Sb and phthalate ester concentrations in drinking water do not exceed the health limit values in force. Although excellent detection limits can be achieved for phthalate ester determination, due to their ubiquity, results are primarily affected by laboratory cross-contamination. Recent investigations suggest that drinking water stored in PET bottles does not possess either genotoxic or estrogenic activity.     

Grain boundary diffusion induced reaction layer formation in Fe/Pt thin films

The solid-state reaction in Pt(15 nm)/Fe(15 nm) and Pt(15 nm)/Ag(10 nm)/Fe(15 nm) thin films after post-annealing at 593 K and 613 K for different annealing times has been studied. The structural properties of these samples were investigated by various methods including depth profiling with secondary neutral mass spectrometry, transmission electron microscopy, and X-ray diffraction. It is shown that after annealing at the above temperatures where the bulk diffusion processes are still frozen, homogeneous reaction layers of FePt and FePt with about 10 at.% Ag, respectively, have been formed. Corresponding depth profiles of the element concentrations revealed strong evidence that the formation mechanism is based on a grain boundary diffusion induced solid-state reaction in which the reaction interfaces sweep perpendicularly to the original grain boundary. Interestingly, X-ray diffraction indicated that in both thin-film systems after the solid-state reaction the ordered L1₀ FePt phase, which is the requested phase for future magnetic data storage applications, is also present.     

First liquid crystalline cuneane‐caged derivatives: a structure–property relationship study

The synthesis and phase behaviour of the first cuneane derivatives having liquid crystalline properties are reported. This new class of liquid crystalline materials is the homologous series of bis[4‐(n‐alkoxyphenyl)]cuneane‐2,6‐dicarboxylates. They were synthesized by two methods: either by isomerization of the previously prepared bis[4‐(n‐alkoxyphenyl)]cubane‐1,4‐dicarboxylates or by direct esterification of the cuneane‐2,6‐dicarboxylic acid. Enantiotropic nematic phases were observed for the first four homologues. The higher homologues exhibited enantiotropic smectic A phases. The bis[4‐(n‐octylphenyl]cuneane‐2,6‐dicarboxylate exhibited the SmA phase at a lower temperature than its octyloxy analogue. The mesophases were investigated and established by polarizing optical microscopy, differential scanning calorimetry and X‐ray diffraction. Quantum chemical calculations suggest elongated structure for these new liquid crystalline compounds.