Regioselective synthesis of 4-aryl-3,4-dihydro-1,3,5-triazino[2,1-<Emphasis Type="Italic">a</Emphasis>]isoindol-2-ones

The condensation of binucleophilic 3-amino-1-arylimino-1H-isoindoles with bifunctional 1-chloro-benzylisocyanates occurs regioselectively resulting in 3,4-dihydro-1,3,5-triazino[2,1-a]isoindol-2-one derivatives. The structures of the synthesized compounds were unambiguously established by NOE experiments. Correspondence: Olha V. Hordiyenko, Chemistry Department, Kyiv National Taras Shevchenko University, 01033 Kyiv, Ukraine.     

Modelling of the frictional heating generated in rolling contact

The transformation of the frictional energy into the heating is a problem of continued technical interest. This problem in the case of the pure sliding contact is widely discussed in many papers. In the case of rolling contact, the frictional heating is due to the slip between the rollers. Since the value of slip is unknown, the problem is more complicated, it becomes non-linear. The paper presents a new mathematical model of the generation of the heat during the rolling problem. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Effect of pore distribution on the statistics of peak stress and overall properties of porous material

This paper addresses the effect of pore distribution on the overall properties and local stress fields in a porous material. Thermal and elastic fields in materials with uniform microstructure are compared with those of materials containing distinguishable clusters of circular or elliptic shape. The numerical simulation combines multipole expansion of local fields with the multi-particle unit cell method. Our work demonstrates that statistics of the peak stresses follow Gumbel’s rule derived for statistics of extreme values and are directly related to statistics of nearest neighbors. Based on this correspondence, an analytical expression for statistics of maximal stresses in a porous material with arbitrary microstructure is constructed in terms of porosity and statistics of minimal distances between the nearest neighbors. At the same time, the numerical analysis indicates that overall elastic constants and thermal (or electrical) conductivity are almost insensitive to the actual distribution of pores – uniform or with distinguishable pore clusters – at least in the examined interval of porosity (up to 50%).     

Diagonals of separately pointwise Lipschitz mappings

It is proved that, for a metric space X and a normed space Z, the diagonals of pointwise Lipschitz mappings f : X ²? →?Z are exactly stable pointwise limits of pointwise Lipschitz mappings. The joint Lipschitz property of separately pointwise Lipschitz mappings f : X?×?Y?→?Z, where X, Y, and Z are metric spaces, is investigated.     

Simultaneous identification of historical pigments Prussian blue and indigo in paintings by electrospray mass spectrometry

A new analytical protocol for identification of Prussian blue (PB) and indigo was proposed. Pigments useful for dating of artworks were detected by flow injection analysis/electrospray ionization mass spectrometry after alkalization of their suspensions in water, decomposition of PB to iron (III) hydroxide and hexacyanoferrate (II) and reduction of indigo to soluble leucoindigo using sodium dithionite. Limits of detection (PB 47 pg, indigo 59 pg) complied with requirements for analysis of microsamples of historical paintings. Potential of the developed method was proven in analysis of blue samples of two oil paintings from the 20^th century. Further, PB was confirmed in a microsample from a painting of ‘Crucifixion’, St. Sebestian church on St. Hill in Mikulov, Czech Republic. Copyright © 2013 John Wiley & Sons, Ltd.     

Chain-growth polymerization of unusual anion-radical monomers based on naphthalene diimide: a new route to well-defined n-type conjugated copolymers

Strongly electron-deficient (n-type) main-chain π-conjugated polymers are commonly prepared via well-established step-growth polycondensation protocols which enable limited control over polymerization. Here we demonstrate that activated Zn and electron-deficient brominated thiophene-naphthalene diimide oligomers form anion-radical complexes instead of conventional Zn-organic derivatives. These highly unusual zinc complexes undergo Ni-catalyzed chain-growth polymerization leading to n-type conjugated polymers with controlled molecular weight, relatively narrow polydispersities, and specific end-functions.     

Crystal Structure and Non-Hydrostatic Stress-Induced Phase Transition of Urotropine Under High Pressure

High-pressure behavior of hexamethylenetetramine (urotropine) was studied in situ using angle-dispersive single-crystal synchrotron X-ray diffraction (XRD) and Fourier-transform infrared absorption (FTIR) spectroscopy. Experiments were conducted in various pressure-transmitting media to study the effect of deviatoric stress on phase transformations. Up to 4 GPa significant damping of molecular librations and atomic thermal motion was observed. A first-order phase transition to a tetragonal structure was observed with an onset at approximately 12.5 GPa and characterized by sluggish kinetics and considerable hysteresis upon decompression. However, it occurs only in non-hydrostatic conditions, induced by deviatoric or uniaxial stress in the sample. This behavior finds analogies in similar cubic crystals built of highly symmetric cage-like molecules and may be considered a common feature of such systems. DFT computations were performed to model urotropine equation of state and pressure dependence of vibrational modes. The first successful Hirshfeld atom refinements carried out for high-pressure diffraction data are reported. The refinements yielded more realistic C−H bond lengths than the independent atom model even though the high-pressure diffraction data are incomplete.