Comparison between biokinetics of inhaled plutonium nitrate and gadolinium oxide in humans and animals

Due to the paucity of human data after inhalation of different chemical forms of radionuclides, the implications for human exposure are often based on animal studies. This paper describes biokinetic studies of plutonium nitrate and gadolinium oxide in human volunteers and rats. The results, together with information from other studies with radionuclides, suggests that animal studies can be used with advantage for assessing the biokinetic behavior in humans, and for providing guidance on the assessment of intake and optimal monitoring regimens.     

Bistrifluoromethylcyclopropenes

Hexafluorobut-2-yne reacts with dichlorocarbene [generated by thermal decomposition of the silane CC1₃SiF₃] to give 3,3-dichlorobistrifluoromethyl- (I) and 1,3-dichlorobistrifluoromethyl-cyclopropene (II).

The 3,3-dichloro-compound (I) is isomerised to (II) by heat, light, or chemical catalysis, but high yields of either pure cyclopropene may be obtained by modification of the reaction conditions. The cyclopropenium ion (III) is formed when either (I) or (II) is treated with antimony pentafluoride.Both (I) and (II) undergo free-radical addition of halogens, but the slow reaction of (II) with trifluoromethyl radicals gives a mixture of products. Nucleophilic substitution of chloride ion from both cyclopropenes occurs very readily, and with ethoxide ions both mono- and di-ethoxybistrifluoromethylcyclopropenes are obtained. The cyclopropenes also react with fluoride ion, iodide ion, or Grignard compounds.     

Hyperfine splitting of 57Fe3+ Mössbauer spectra in diamagnetic host lattices

The Mössbauer spectra of ⁵⁷Fe³⁺ substituted in 0.2 to 0.4 atom % of the octahedral sites in the host lattices Na_0.9Mg_0.45Ti_1.55O₄, TiO₂, Sc₂O₃, LiScO₂ and MgAl₂O₄ have been examined. Hyperfine splittings of the spectra were observed for all cases except Sc₂O₃. In all cases the electron spin resonance spectrum was found, or has been shown to be highly anisotropic as a result of the presence of strong axial or rhombic fields and consequent splitting of the 3d⁵ ground state energy levels. In several cases resolution of the $\text{±}\text{5}\text{2}$ and $\text{±}\text{3}\text{2}$ Mössbauer spectra was observed. Mössbauer spectra of the solid solutions Na_0.9Mg_0.45Ti_1.55O₄Na_0.9Fe_0.9Ti_1.1O₄, LiScO₂LiFeO₂ and TiO₂FeNbO₄ have also been examined.     

Cyclopropane chemistry. Part 5 [1,2]. Hexafluorocyclopropane as a source of difluorocarbene

Thermolysis of hexafluorocyclopropane in the presence of ethylene, propene, vinyl chloride, and vinyl bromide gives good yields of the corresponding 1,1-difluorocyclopropanes, formed by addition of difluorocarbene to the olefin. The tetrafluoroethylene formed dimerises to octafluorocyclobutane, co-dimerises with the olefin, or survives, depending on the reaction conditions. With allene, hexafluorocyclopropane gives 1-(difluoromethylene)cyclopropane, 2,2,3,3-tetrafluorospiropentane, and products derived from tetrafluoroethylene and allene.     

Synthesis and Ambiphilic Reactivity of Metalated Diorgano-Phosphonite Boranes

Unprecedented metalated phosphonite boranes were prepared from PH-substituted precursors and silyl amides. Although potassium derivatives were thermally stable and could even be isolated and structurally characterised, lithiated analogues proved to be unstable towards self-condensation under cleavage of LiOR at ambient temperature. Reaction studies revealed that the metalated phosphonite boranes exhibit ambiphilic character. Their synthetic potential as nucleophilic building blocks was demonstrated in the synthesis of the first stannylated phosphonite representing a new structural motif in phosphine chemistry.     

Co-crystallisation as a modular approach to the discovery of spin-crossover materials

Herein we present co-crystallisation as a strategy for materials discovery in the field of switchable spin crossover (SCO) systems. Using [Fe(3-bpp)₂]·2A (where 3-bpp = 2,6-bis(pyrazol-3-yl)pyridine, A = BF₄⁻/PF₆⁻) as a starting point, a total of 11 new cocrystals have been synthesised with five different dipyridyl coformers. Eight of these systems show spin crossover behaviour, and all show dramatically different switching properties from the parent complex. The cocrystals have been studied by variable temperature single-crystal X-ray diffraction and SQUID magnetometry to develop structure–property relationships. The supramolecular architecture of the cocrystals depends on the properties of the coformer. With linear, rigid coformer molecules leading to 1D supramolecular hydrogen-bonded chains, while flexible coformers form 2D sheets and bent coformers yield 3D network structures. The SCO behaviour of the cocrystals can be modified through changing the coformer and thus co-crystallisation presents a rapid, facile and highly modular tool for the discovery of new switchable materials. The wider applicability of this strategy to the design of hybrid multifunctional materials is also discussed.

The switching behaviour of spin crossover cocrystals can be modified through changing the coformer and thus co-crystallisation presents a rapid, facile and highly modular tool for the discovery of new switchable materials.     

A density matrix approach to the Goldanskii-Karyagin effect

A density matrix formalism has been introduced to describe the perturbation of the Mössbauer line intensities caused by the anisotropic recoilless fraction in random absorbers. General properties of the matrix elements are discussed and relationships between thermal tensors and density matrices are investigated with the attention focused on the possibility to extract as much information about the thermal tensors as possible from the observed line intensities. It is shown, that quartic (anharmonic) anisotropy may be observable in quadrupolarly dominated transitions under favourable conditions.     

A 57Fe and 119Sn Mössbauer study of BaFe4Sn2O11

The Mössbauer spectrum of BaFe₄Sn₂O₁₁ has been recorded for both ⁵⁷Fe and ¹¹⁹Sn isotopes at a variety of temperatures. In the paramagnetic state the ⁵⁷Fe spectra are interpreted in terms of three iron environments. Magnetic ordering begins at 77 K and is virtually complete by 4.2 K to give an average magnetic hyperfine field of 504 kG. The ¹¹⁹Sn spectra also reflect the magnetic ordering and a magnetic hyperfine field of 45 kG is transferred to the tin nuclei.     

57Fe Mössbauer study of f-riebeckite

F-riebeckite has been subjected to analysis by 57-Fe Moessbauer spectroscopy from 4. 2K to 501K. The spectra obtained above the magnetic transition temperature, were analyzed in terms of three ferrous doublets in M1, M3 and M2 sites and two ferric doublets occupying M2 and M1 sites. The ratios of these occupations, together with their quadrupole splittings, were then used to fit the 4.2K magnetic spectrum.