NMR at very low fields

Although nuclear magnetic resonance in low fields around or below the Earth's magnetic field is almost as old as nuclear magnetic resonance itself, the recent years have experienced a revival of this technique that is opposed to the common trend towards higher and higher fields. The background of this development is the expectation that the low-field domain may open a new window for the study of molecular structure and dynamics. Here, we will give an overview on the specific features in the low-field domain, both from the technical and from the physical point of view. In addition, we present a short passage on the option of magnetic resonance imaging in fields of the micro-Tesla range.     

In vivo Toxicity Evaluation of a Nano-drug Delivery System Using a Caenorhabditis elegansModel System

Drug carrier materials need to possess good biological safety. Presently, most biosafety evaluation studies use rodent animal models, including rats and rabbits. However, the cost of raising these animals is relatively high and the experimental period is long. Caenorhabditis elegans(C. elegans) presents an ideal toxicological evaluation model due to its simple structure, easy cultivation, short life cycle, and evolutionary conservation. In this paper, we used C. elegans to test the biological safety of our pH-responsive carrier system(FFPFF self-assembling into a nanosphere structure, FFPFF Nps), which was designed for anti-tumor drug delivery. Our results showed that exposure to high doses of FFPFF Nps did not have a significant impact on the survival rate, growth, development, movement, and reproduction of C. elegans. The preliminary evaluation of the overall biological model of C. elegans shows that FFPFF Nps has good biological safety and warrants further study.     

核壳纳米球钴基金属有机聚合物的制备及其储锂性能

以偏苯三甲酸和六水合硝酸钴为原料,通过水热法合成了2种反应时间不同的钴基金属有机聚合物(Co-MOP)。采用X射线衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)和N₂吸附-脱附对Co-MOP材料进行了结构和形貌表征。将2种Co-MOP材料用作锂离子电池负极材料,并进行了电化学性能测试。结果表明,Co-MOP-12(水热反应12 h)展示出了优异的电化学性能,在100 mA·g^-1的电流密度下,Co-MOP-12电极的首圈可逆比容量达到979 mAh·g^-1,循环100圈后比容量高达1 345 mAh·g^-1。     

Chemo- and Site-Selective Electro-Oxidative Alkane Fluorination by C(sp3)−H Cleavage

Electrochemical fluorinations of C(sp³)−H bonds with a nucleophilic fluoride source have been accomplished in a chemo- and site-selective fashion, avoiding the use of electrophilic F⁺ sources and stoichiometric oxidants. The introduced metal-free strategy exhibits high functional group tolerance, setting the stage for late-stage fluorinations of biorelevant motifs. The synthetic utility of the C(sp³)−H fluorination was reflected by subsequent one-pot arylation of the generated benzylic fluorides.     

Application of a capillary gas chromatographic-selected-ion recording mass spectrometric technique to the analysis of diethylstilbestrol and its phosphorylated precursors in plasma and tissues

A method for the analysis of diethylstilbestrol (DES) which is suitable for pharmacokinetic studies has been developed using capillary gas chromatographic (GC) separation and detection with selected-ion mass spectrometry (MS). This technique has been applied to a variety of samples including human plasma samples and extracts of animal tissues including prostate and liver. To investigate the pharmacokinetics of stilphostrol (diethylstilbestrol diphosphate) we have modified the GC-MS method in two ways. One modification involves a dual assay for DES; the first a direct assay, and the second after hydrolysis of a sample with alkaline phosphatase. The difference in these values is the amount of phosphorylated DES present. The other modification separates stilphostrol and DES using a reversed-phase, ion-paired high-performance liquid chromatographic method followed by alkaline phosphatase hydrolysis followed by the GC-MS method. The details of these three methods are described and some representative data are shown.     

Die chemie der schweren carben-analogen R2M,M = Si,Ge, Sn: IX. Eigenschaften und thermolyse von neuen 7-silabicyclo[2.2.1]heptadienen

Factors governing the ease and mechanism of 7-silabicyclo[2.2.1]heptadienes thermolysis in order to generate free silylenes and the corresponding benzene derivatives are investigated. For this purpose, 29 new compounds of the types VII–X have been prepared. No indications for a polar mechanism or an intermediate biradical could be found. The degradation is exactly of first order in all cases investigated sofar, and is enhanced by phenyl groups at the bridgehead C atoms, if a conformation coplanar with the basic ring is allowed by the neighbouring substituents, but is not enhanced by phenyl groups at the Si. The X-ray structure of two typical derivatives is discussed with this respect. A special mechanism is operating in the easy thermolysis of carbomethoxy-substituted compounds leading to cyclic sila enolether intermediates.     

Zur Kenntnis der Strontiumpolysulfide Präparative,röntgenographische und schwingungsspektroskopische Untersuchungen

X-ray, I.R., and Raman Data of Strontium Polysulfides The strontium polysulfides SrS₂, SrS₃A, and SrS₃B were studied in terms of preparation, thermal decomposition, and phase transition. The i.r. and Raman spectra of the strontium polysulfides as well as the normal coordinates of the phonon modes are presented and discussed in comparison with the respective barium compounds. From the spectra it is shown that S₃^2? entities are present in SrS₃A as in SrS₃B.     

Structurally Modelling the 2-His-1-Carboxylate Facial Triad with a Bulky N,N,O Phenolate Ligand

We present the synthesis and coordination chemistry of a bulky, tripodal N,N,O ligand, Im^Ph2NNO ^{t Bu} ( L ), designed to model the 2-His-1-carboxylate facial triad (2H1C) by means of two imidazole groups and an anionic 2,4-di-tert-butyl-subtituted phenolate. Reacting K-L with MCl₂ (M = Fe, Zn) affords the isostructural, tetrahedral non-heme complexes [Fe(L)(Cl)] ( 1 ) and [Zn(L)(Cl)] ( 2 ) in high yield. The tridentate N,N,O ligand coordination observed in their X-ray crystal structures remains intact and well-defined in MeCN and CH₂Cl₂ solution. Reacting 2 with NaSPh affords a tetrahedral zinc thiolate complex, [Zn(L)(SPh)] ( 4 ), that is relevant to isopenicillin N synthase (IPNS) biomimicry. Cyclic voltammetry studies demonstrate the ligand's redox non-innocence, where phenolate oxidation is the first electrochemical response observed in K-L , 2 and 4 . However, the first electrochemical oxidation in 1 is iron-centred, the assignment of which is supported by DFT calculations. Overall, Im^Ph2NNO ^{t Bu} provides access to well-defined mononuclear, monoligated, N,N,O-bound metal complexes, enabling more accurate structural modelling of the 2H1C to be achieved.