X‐Ray Crystal Structure Analysis of Oxindole Alkaloids

The single‐crystal X‐ray structures of speciophylline, mitraphylline, and rhynchophylline, oxindole alkaloids from the Peruvian climbing vine Uncaria tomentosa (Rubiaceae), were determined. The three compounds show N???H? N hydrogen bonding, which has not been observed in the crystal structures of the related alkaloids pteropodine and isopteropodine. In the tetracyclic alkaloid rhynchophylline, the side chain is rotated out of the ring plane into a position perpendicular to it. This is in contrast to the situation of the pentacyclic analogue mitraphylline, which possesses a conformationally rigid tricyclic core. This conformational difference possibly causes the competitive antagonism of these two types of alkaloids.     

X‐Ray Diffraction as a Local Probe Tool

For the structural characterization of nanoscale objects, X‐ray diffraction is widely used as a technique complementing local probe analysis methods such as scanning electron microscopy and transmission electron microscopy. Details on strain distributions, chemical composition, or size and shape of nanostructures are addressed. X‐ray diffraction traditionally obtains very good statistically averaged properties over large ensembles—provided this averaging is meaningful for ensembles with sufficiently small dispersion of properties. In many cases, however, it is desirable to combine different analysis techniques on exactly the same nano‐object, for example, to gain a more detailed insight into the interdependence of properties. X‐ray beams focused to diameters in the sub‐micron range, which are available at third‐generation synchrotron sources, allow for such X‐ray diffraction studies of individual nano‐objects.     

ChemInform Abstract: Structural Characterization of Moganite‐Type AlPO4 by NMR and Powder X‐Ray Diffraction.

A new high‐pressure AlPO₄ phase obtained at 5 GPa and 1500 °C is characterized by synchrotron powder XRD and MAS NMR spectroscopy.     

Microfocus X‐Ray Scattering Scanning Microscopy for Polymer Applications

Summary: The fracture properties of polymers are one of the key parameters that define their service life and limit their applications. One of the most interesting and important questions is how the molecular architecture and the structure of polymers at nanolength scales influence their fracture properties. X‐ray scattering is a powerful means of probing bulk structures at the nanometre scale. It can therefore provide a wealth of information relating to such structure‐property relationships. In the present study, synchrotron radiation microfocus small‐angle X‐ray scattering is used to investigate the damage area ahead and around the crack tip in polyamide 6 (PA6). The results reveal that the damage area propagates far beyond the visible crack, and inside the damaged zone platelet‐shaped cracks/voids are formed.

     

Syntheses and X‐Ray Structures of Zinc Amidinate Complexes

Reactions of ZnX₂ (X = Cl, Br) with equimolar amounts of Li[t‐BuC(NR)₂] (R = i‐Pr, Cy) yielded mono‐amidinate complexes [{t‐BuC(NR)₂}ZnX]₂ (X = Cl, R = i‐Pr 1 , Cy 2 ; X = Br, R = i‐Pr 3 , Cy 4 ), whereas reactions with two equivalents of Li‐amidinate resulted in the formation of the corresponding bis‐amidinate complexes [t‐BuC(NR)₂]₂Zn (R = i‐Pr 5 , Cy 6 ). 1 ‐ 6 were characterized by elemental analyses, IR, mass and multinuclear NMR spectroscopy (¹H, ¹³C), and single crystal X‐ray analysis ( 1 , 2 , 3 , 6 ). In addition, the single crystal X‐ray structure of [t‐BuC(NCy)₂]ZnBr·LiBr(OEt₂)₂ 7 , which was obtained as a byproduct in low yield from re‐crystallization experiments of 4 in Et₂O, is reported.     

Phosphoramidates: Synthesis,spectroscopy, and X‐Ray crystallography

A series of novel phosphoramidates with a general formula P(O)X₁X₂X₃, where X₁ = X₂ = X₃ = 1H‐1,2,4‐triazol ( 1 ); X₁ = X₂ = X₃ = N‐phenylhydrazine ( 2 ); X₁ = Br, X₂ = X₃ = N‐phenylhydrazine ( 3 ), X₁ = Br, X₂ = X₃ = dipropylamine ( 4 ), and X₁ = X₂ = X₃ = 1,4‐dioxa‐8‐azaspiro[4.5]decane ( 5 ) as well as [P(O)(NC₄H₈NH‐CH₃)⁺₃.3Cl^‐] ( 6 ), were synthesized and characterized by ¹H, ¹³C, ³¹P NMR, IR spectroscopy, and elemental analysis. It is interesting that the P atoms of compounds 3 and 4 are the most upfielded atoms (δ(³¹P) = −23.00, −21.65 ppm) among molecules 1–6 . This indicates that the Br atom acts as a strong electron donor to the P atom via a resonance interaction. The ¹H and ¹³C NMR spectra of compound 5 reveal three separate sets of peaks for the aliphatic CH² protons of three four‐membered rings. This can be explained by different spatial orientations (conformations) of the aliphatic rings. The crystal structure of compound 6 was also determined by X‐ray crystallography. There are intermolecular N H ···Cl hydrogen bonds in this structure. © 2012 Wiley Periodicals, Inc. Heteroatom Chem 23:478–485, 2012; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.21040     

The Dawn of X‐Ray Astronomy (Nobel Lecture)

Riccardo Giacconi joined the American Science and Engineering Corporation (AS & E) after leaving Princeton University in 1959, and in 1962 his group there detected the first extrasolar Xray source. Prof. Giacconi was subsequently responsible for the launch and use of the satellite UHURU (1970) and the EINSTEIN observatory (1978). He was appointed Associate Director of the High Energy Astrophysics Division of the Harvard‐Smithsonian Center for Astrophysics in 1973 and was also appointed Professor of Astronomy at Harvard University that same year. In 1981 he became the first Director of the Space Telescope Science Institute and was also appointed Professor in the Department of Physics and Astronomy at Johns Hopkins University. In 1992 he was appointed Director General of the European Southern Observatory, an intergovernmental organization of eight nations. Prof. Giaconni is currently President of Associated Universities, Inc., and Research Professor at Johns Hopkins University. He was awarded the Wolf Prize in 1987, and the Nobel Prize for Physics in 2002.     

In Situ Synchrotron Radiation X‐Ray Microspectroscopy of Polymer Microcontainers

Direct, real‐time analytical techniques that provide high‐resolution information on the chemical composition and submicrometer structure of various polymer micro‐ and nanoparticles are in high demand in a range of life science disciplines. Synchrotron‐based scanning transmission X‐ray microspectroscopy (STXM) combines both local‐spot chemical information (assessed via near‐edge X‐ray absorption fine structure spectroscopy) and imaging with resolution of several tens of nanometers, and thus can yield new insights into the nanoscale properties of these materials. Furthermore, this method allows in situ examination of soft‐matter samples in aqueous/gaseous environments and under external stimuli, such as temperature, pressure, ultrasound, and light irradiation. This Minireview highlights some recent progress in the application of the STXM technique to study the temperature‐dependent behavior of polymer core–shell microcapsules and to characterize the physicochemical properties of the supporting shells of gas‐filled microbubbles in their natural hydrated state.     

Solution NMR and X‐Ray Structural Studies on Phthalocyaninatoiron Complexes

The addition of primary amines as solubilizing reagents for phthalocyaninatoiron complexes is shown to afford six‐coordinate bis(amine)phthalocyaninato complexes, i.e., [Fe(amine)₂(pc)] 2 (amine = decan‐1‐amine) and 3 (amine = benzylamine), with the two new N‐donors occupying the trans‐axial positions. The new complexes were characterized by extensive NMR measurements in THF solution. For complex 3 with the benzylamine ligand, the solid‐state structure was determined by X‐ray diffraction methods. Complex 2 is sufficiently labile in THF solution to exchange one amine ligand against CO (gas) affording an equilibrium mixture containing [Fe(amine)(CO)(pc)] 4 .     

X‐Ray and Electron Diffraction Study of Poly(p‐dioxanone)

Summary: Solution‐grown lamellar crystals of poly(p‐dioxanone) (PPDX) have been crystallized isothermally from butane‐1,4‐diol at 100 °C. The crystal structure of PPDX has been determined by interpretation of X‐ray fiber diagrams of PPDX fibers and electron diffraction diagrams of lozenge‐shaped chain‐folder lamellar crystals. The unit cell of PPDX is orthorhombic with space group P2₁2₁2₁ and parameters: a = 0.970 nm, b = 0.742 nm, and c (chain axis) = 0.682 nm. There are two chains per unit cell, which exist in an antiparallel arrangement.

Transmission electron micrograph of PPDX chain‐folded lamellar crystals obtained by isothermal crystallization and its electron diffraction diagram.     

Synchronous Chemoradiation Nanovesicles by X‐Ray Triggered Cascade of Drug Release

The approach of concurrent‐to‐synchronous chemoradiation has now been advanced by well‐designed nanovesicles that permit X‐ray irradiation‐triggered instant drug release. The nanovesicles consist of Au nanoparticles tethered with irradiation labile linoleic acid hydroperoxide (LAHP) molecules and oxidation‐responsive poly(propylene sulfide)‐poly(ethylene glycol) (PPS‐PEG) polymers, where DOX were loaded in the inner core of the vesicles (Au‐LAHP‐vDOX). Upon irradiation, the in situ formation of hydroxyl radicals from LAHP molecules triggers the internal oxidation of PPS from being hydrophobic to hydrophilic, leading to degradation of the vesicles and burst release of cargo drugs. In this manner, synchronous chemoradiation showed impressive anticancer efficacy both in vitro and in a subcutaneous mouse tumor model by one‐dose injection and one‐time irradiation.