Fluorine containing coordination compounds of Cr(III)

Trans-[Cr(NH₃)₄F₂]I·H₂O (A) has monoclinic P2_l/m (No. 11) space group witha=5.033 (3),b=16.333 (10),c=5.539 (3) Å and =98.47 (3)°,Z=2.Cis-[Cr(NH₃)₄F₂]ClO₄ (B) has tetragonal space group I4_lmd (No. 109) witha=7.417 (1),c=16.610 (2) Å,Z=4. Cr–F and Cr–N bonding distances are 1.894 (3); 2.087 and 2.083 (5) Å for A and 1.887 (6); 2.062 (5) and 2.051 (7) Å for B. Octahedral angles within the cations are close to 90° for both compounds. Cr–N bondtrans to Cr–F bond in thecis compound is shorter. Structures were refined toR ₂ values of 0.072 (A) and 0.058 (B).Trans-[Cr(NH₃)₄F₂]I·H₂O has weak N–H–F hydrogen bonds between the cations. None such interactions were found incis-[Cr(NH₃)₄F₂]ClO₄.

---

Fluorhältige Komplexe des Cr(III), 2. Mitt.: Kristall- und Molekülstruktur von trans-[Cr(NH₃)₄F₂]I·H₂O und cis-[Cr(NH₃)₄F₂]ClO₄

Zusammenfassung Trans-[Cr(NH₃)₄F₂]I·H₂O (A) kristallisiert in der Raumgruppe P2_l/m (No. 11) mitZ=2 unda=5,033 (3),b=16,333 (10),c=5,539 (3) Å und =98,47 (3)°.Cis-[Cr(NH₃)₄F₂]ClO₄ (B) kristallisiert in der Raumgruppe I4_lmd (No. 109) mitZ=4,a=7,417 (1) undc=16,610 (2) Å. Die Cr–F- und Cr–N-Abstände sind 1,894 (3); 2,087 (6), 2,083 (5) Å für A und 1,887 (6); 2,062 (5), 2,051 (7) Å für B. Die octaedrischen Bindungswinkel innerhalb der Kationen weichen nicht viel von 90° ab. Der Cr–N-Abstand intrans-Position der Cr–F-Bindung ist kürzer. Die Strukturen wurden bis zu GütefaktorenR ₂ 0,072 (A) und 0,058 (B) verfeinert. Bei der Verbindung A wurden schwache N–H ... F-Wasserstoff-Bindungen zwischen verschiedenen Kationen beobachtet, während bei der Verbindung B keine Wasserstoff-Bindungen vorhanden sind.

     

Antiferromagnetism of poly(3-dodecylthiophene) irradiated by γ-beams

The magnetic properties of poly(3-dodecyl-thiophene) (PDDT) irradiated by -beams have been studied by measuring the magnetic susceptibility and EPR spectra. The irradiated PDDT is characterized, similarly as the non-irradiated one, by an antiferromagnetic course of magnetic susceptibility with a Néel temperature of 237 K. It is suggested that the antiferromagnetic properties of PDDT are caused by transformation of polarons to bipolarons, which takes place at lower temperatures.     

Influence of Al2O3 Nanoparticles on the Thermal Stability of Ultra-Fine Grained Copper Prepared by High Pressure Torsion

Summary.  Ultra-fine grained (UFG) Cu (grain size 80 nm) containing 0.5 wt.% Al₂O₃ nanoparticles (size 20 nm) was prepared by high pressure torsion (HPT). Positron lifetime spectroscopy was employed to characterize the microstructure of this material, especially with respect to types and concentration of lattice defects. The evolution of microstructure with increasing temperature was studied by positron lifetime spectroscopy and X-ray diffraction measurements. The thermal stability of the Cu + 0.5 wt.% Al₂O₃ nanocomposite was compared with that of pure UFG Cu prepared by the same technique. The processes taking place during thermal recovery of the initial nanoscale structure in both studied materials are described. Received October 5, 2001. Accepted (revised) December 20, 2001     

A Study of PbTiO3 Crystallization in Pure and Composite Nanopowders Prepared by the Sol-Gel Technique

Summary.  In this investigation the crystallization of PbTiO₃ upon annealing of pure nanopowders and PbTiO₃–SiO₂ (1:1 v/v) nanocomposite powders prepared by the sol-gel technique was studied. Using X-ray diffraction phase analysis, the start of PbTiO₃ crystallization in pure PbTiO₃ powders was detected at 400°C. Distinct crystallization of PbTiO₃ in PbTiO₃–SiO₂ nanocomposites starts at 700°C, whereas SiO₂ remains amorphous. There are indications that an interface interaction between the PbTiO₃ and the SiO₂ phase plays an important role in hindering the crystallization of PbTiO₃. The particle size (size of coherently scattering regions) was estimated from the broadening of the X-ray diffraction line profiles. The average size of PbTiO₃ nanocrystallites increases with temperature and time of annealing, the influence of temperature being more significant than that of the annealing time. Differential scanning calorimetry confirmed the results of the X-ray diffraction with respect to the start of the crystallization. Laser beam scattering and scanning electron microscopy provided the statistical distribution of the grain size and the morphology of the powder grains, showing that each grain of the powders contains several nanocrystallites (coherently scattering regions). Received October 4, 2001. Accepted (revised) December 14, 2001     

On the modification of solid adsorbents with volatile organics II. The role of the layer adsorbed

Summary This paper presents a continuation of our research dedicated to solid-adsorbent surface modification with what are commonly regarded as volatile and easily eluted organic compounds. Two porous adsorbents were used: natural zeolite (clinoptilolite) and alumina, while the adsorbates employed were n-hepatane and benzene. The results show that a simple injection of volatile adsorbate greatly alters the solid surface adsorption properties. The consequences of volatile modifier application are discussed on the grounds of adsorption isotherms determined at 313K. Possible implications to the tailor made adsorbents are outlined as well.Part I, J. Chromatogr.442, 105 (1988)     

Determination of radiation yields of ionogenic products of two-phase water-tributylphosphate and water-di-(2-ethylhexyl)-phosphoric acid systems by capillary isotachophoresis

It was found that the main ionogenic radiolytical degradation products of tributylphosphate were monobutylphosphate dibutylphosphate, phosphoric acid, formic, acetic, propionic and butyric acids as the result of gamma-irradiation of two-phase water-tributylphosphate system. In the case of irradiation of two-phase water-di(2-ethylhexyl)-phosphoric acid system, the main radiolytic degradation products are 2-ethylhexylphosphoric acid and phosphoric acid. All products were determined using isotachophoresis. According two-phase theory the total and partial radiation yields of products were calculated from the results.Dedicated to 65th birthday of prof. L. T. Bugaenko     

Mercury Speciation in Fish by High-Performance Liquid Chromatography (HPLC) and Post-Column Ultraviolet (UV)-Photochemical Vapor Generation (PVG): Comparison of Conventional Line-Source and High-Resolution Continuum Source (HR-CS) Atomic Absorption Spectrometry (AAS)

An ultraviolet-photochemical generator (UV-PVG) capable of post-column on-line transformation of both organic and inorganic mercury species to cold vapor (Hg⁰) with subsequent detection by quartz tube-atomic absorption spectrometry (QT-AAS) was developed. Mercury(II), methylmercury(I), ethylmercury(I), and phenylmercury(I) were successfully detected after separation by reversed-phase high-performance liquid chromatography (RP-HPLC). Two types of AAS detectors were compared. The first was a commonly used line-source instrument while the second was a high-resolution continuum source (HR-CS) AAS. The latter provided better limits of detection: 0.47?µg?L^?1 for Hg(II), 0.84?µg?L^?1 for methylmercury(I), 0.80?µg?L^?1 for ethylmercury(I), and 2.0?µg?L^?1 for phenylmercury(I). The repeatability at 30?μg?L^?1 was 3.6%, 4.1%, 6.2%, and 4.5% for these species (n?=?10). These figures of merit were comparable with those reported for more sensitive atomic fluorescence spectrometry. Nine sample extraction procedures were investigated. Extraction by tetramethylammonium hydroxide and HCl at 75?°C was selected as the only method compatible with the proposed separation and detection steps providing high extraction efficiency and no changes in mercury speciation. The applicability of the proposed high-performance liquid chromatography–ultraviolet-photochemical vapor generation–quartz tube-atomic absorption spectrometry method was demonstrated using fish samples and certified reference materials (CRM) DOLT-4 (dogfish liver) and ERM-CE464 (tuna fish). The results were comparable to those obtained by a reference method based on L-cysteine extraction and high-performance liquid chromatography–inductively coupled plasma-mass spectrometry (HPLC–ICP-MS) determination.     

Determination of configuration-dependent spin-orbit interaction constants by atomic spectroscopy

A new approach to the evaluation of spin-orbit interaction (SOI) constants is presented. The SOI constants ξ_p and ξ_d of 4p and 3d electrons have been evaluated by employing the available atomic spectral data for the first transition row atoms and ions possessing the electron configuration K(2)L(8)3s²3p⁶3d^α4s^β4p^γ.     

Gas phase isomerization of \documentclass{article}\pagestyle{empty}\begin{document}$ \left[{{\rm C}_{{\rm 10}} {\rm H}_{{\rm 14}} } \right]_{}^{_.^ + } $\end{document} ions generated from adamantanoid compounds

\documentclass{article}\pagestyle{empty}\begin{document}$ \left[{{\rm C}_{{\rm 10}} {\rm H}_{{\rm 14}} } \right]_{}^{_.^ + } $\end{document} ions have been generated from a number of adamantanoid compounds, both by ionization and ionization followed-by fragmentation. Metastable ion abundance ratios of competitive reactions indicate the decomposition of these ions from common structures in all cases.     

Production of lepton pairs in processes with hadronic jets

We propose a model for the production of extra (additional) lepton pairs in deep inelastic lepton-hadron scattering, e⁺e^– annihilation and large p_T processes. Extra lepton pairs are supposed to be originated by annihilations of quarks and antiquarks created during the space-time evolution of quark initiated jets. This mechanism yields predominantly dileptons with rather low masses. Predictions following from the model are compared with the recent data on trimuon production in neutrino-nucleon interactions. It is also suggested that internal hard processes can lead to dileptons with both small and large masses. The latter mechanism has rather small cross section but it is particularly interesting from the point of view of the simple quark-parton model.Dedicated to Academician Václav Votruba on the occasion of his seventieth birthday.