(A19N7)[In4]2 (A = Ca,Sr) and (Ca4N)[In2]: Synthesis,Crystal Structures,Physical Properties,and Chemical Bonding

Single phase powders of (A₁₉N₇)[In₄]₂ (A = Ca, Sr) and (Ca₄N)[In₂] were prepared by reaction of melt beads of the metallic components with nitrogen. The crystal structure of (Ca₁₉N₇)[In₄]₂ was refined based on neutron and X‐ray powder diffraction data. The crystal structure of (Sr₁₉N₇)[In₄]₂ was solved from the X‐ray powder pattern. The structure refinements in combination with results from chemical analyses ascertain the compositions. The compounds (A₁₉N₇)[In₄]₂ (A = Ca, Sr) are isotypes of (Ca₁₉N₇)[Ag₄]₂; (Ca₁₉N₇)[In₄]₂ is probably identical to the earlier reported (Ca_18.5N₇)[In₄]₂. The crystal structure of the isotypes (A₁₉N₇)[In₄]₂ (A = Ca, Sr; cubic, , Ca: a = 1471.65(3) pm; Sr: a = 1561.0(1) pm) contains isolated [In₄] tetrahedra embedded in a framework of edge‐ and vertex‐sharing (A₆N) octahedra. Six of these octahedra are condensed by edge‐sharing around one central A²⁺ ion to form “superoctahedra” (A₁₉N₆) which are connected three‐dimensionally via further octahedra by corner‐sharing. The crystal structure of (Ca₄N)[In₂] (tetragonal, I4₁/amd, a = 491.14(4) pm, c = 2907.7(3) pm) consists of alternating layers of perovskite type slabs of vertex‐sharing octahedra (Ca₂Ca_4/2N) and parallel arranged infinite zigzag chains equation/tex2gif-stack-1.gif[In₂]. In the sense of Zintl‐type counting the compounds (A²⁺)₁₉(N^3?)₇[(In^2.125?)₄]₂ present an electron excess, (Ca²⁺)₄(N^3?)[(In^2.5?)₂] is electron deficient. Metallic properties are supported by electrical resistivity and magnetic susceptibility measurements. The analysis of the electronic structures gives evidence for the existence of homoatomic interactions In–In and significant heteroatomic metal–metal interactions Ca–In which favor the deviations of the title compounds from the (8 – N) rule.     

Zur infrarotspektroskopischen Erfassung kleiner Wassergehalte in Benzylalkohol, 1,4-Dioxan, Glykol und Glykolderivaten

Zusammenfassung Die bereits an aliphatischen Alkoholen und Ketonen mit Hilfe eines selbstregistrierenden Infrarotspektralphotometers durchgeführten Untersuchungen zur infrarotspektroskopischen Erfassung kleiner Wassergehalte wurden an den mit Wasser mischbaren organischen Lösungsmitteln Äthylenglykol, Äthylenglykolmonomethyläther, Äthylenchlorhydrin, Glycerin, 1,4-Dioxan und Benzylalkohol fortgesetzt. Für Wasserbestimmungen in diesen Lösungsmitteln erwies sich besonders die OH-Kombinationsschwingung des Wassers im Spektralbereich um 5200 cm^–1 geeignet. Mit Hilfe dieser OH-Absorptionsbande, die Messungen in Küvetten mit Glasfenstern gestattet, können im Direktverfahren Wassergehalte von etwa 1,0–10,0 Vol-% mit guter Genauigkeit, besser als 0,1 Vol-% bestimmt werden; im Kompensationsverfahren sind noch Konzentrationen von 0,1–2,0 Vol-% erfaßbar.Bei dem nicht hydroxylhaltigen 1,4-Dioxan lassen sich mittels dieser Bande Wassergehalte von 0,1–10,0 Vol-% im Direktverfahren bestimmen. Für die quantitative Erfassung sehr kleiner Wassergehalte im Dioxan eignet sich infolge günstiger Eigenabsorptionsverhältnisse besonders gut die OH-Valenzschwingung bei 3600 cm^–1, die hier Wasser-bestimmungen bis herab zu 0,02 Vol-% im Direktverfahren mit hinreichender Genauigkeit ermöglicht.Auch die OH-Deformationsschwingung bei 1600 cm^–1 erweist sich für Wassergehalte von 0,5–10 Vol-% zum qualitativen Nachweis und zur quantitativen Bestimmung verwendbar, soweit bei den betreffenden Lösungsmitteln nicht Fehler durch die Löslichkeit der Steinsalz-Küvettenfenster auftreten.Frühere Mitt.: Wiegel, E., u. H. H. Kirchner: diese Z. 178, 241 (1960/61).     

Nuclear moments and the change in the mean square charge radius of neutron deficient thallium isotopes

The hyperfine structure, isotope and isomeric shifts in the atomic transition 6p ² P _3/2–7s ² S _1/2, =535 nm have been measured for theI=7 andI=2 states of^{190, 192, 194, 196}Tl; theI=1/2 andI=9/2 states of¹⁹¹Tl and the I=7 isomer of¹⁸⁸Tl. The thallium isotopes were prepared as fast atomic beams at the GSI on-line mass separator following fusion reactions and — in some cases — subsequent-decay. The nuclear dipole moments, electric quadrupole moments and the change in the nuclear mean square charge radius are evaluated. Theuu-isotopes show an isomeric shift which changes sign between¹⁹²Tl and¹⁹⁴Tl.Dedicated to P. Armbruster on the occasion of his 60th birthday     

Reaction properties of the trans-hyponitrite complex [Ru2(CO)4(mu-H)(mu-PBu(t)2)(mu-Ph2PCH2PPh2)(mu-eta2-ONNO)

The protonation of [Ru(2)(CO)(4)(mu-H)(mu-PBu(t)()(2))(mu-dppm)(mu-eta(2)-ONNO)] (1) with HBF(4) occurs at the oxygen of the noncoordinating side of the trans-hyponitrite ligand to give [Ru(2)(CO)(4)(mu-H)(mu-PBu(t)()(2))(mu-dppm)(mu-eta(2)-ONNOH)][BF(4)] (2) in good yield. The monoprotonated hyponitrite in 2 is deprotonated easily by strong bases to regenerate 1. Furthermore, 1 reacts with the methylating reagent [Me(3)O][BF(4)] to afford [Ru(2)(CO)(4)(mu-H)(mu-PBu(t)()(2))(mu-dppm)(mu-eta(2)-ONNOMe)][BF(4)] (3). The molecular structures of 2 and 3 have been determined crystallographically, and the structure of 2 is discussed with the results of the DFT/B3LYP calculations on the model complex [Ru(2)(CO)(4)(mu-H)(mu-PH(2))(mu-H(2)PCH(2)PH(2))(mu-eta(2)-ONNOH)](+) (2a). Moreover, the thermolysis of 2 in ethanol affords [Ru(2)(CO)(4)(mu-H)(mu-OH)(mu-PBu(t)()(2))(mu-dppm)][BF(4)] (4) in high yield, and the deprotonation of 4 by DBU in THF yields the novel complex [Ru(2)(CO)(4)(mu-OH)(mu-PBu(t)()(2))(mu-dppm)] (5).     

Zero-temperature magnetic transition in an easy-axis Kondo lattice model

We address the quantum transition of a spin-1/2 antiferromagnetic Kondo lattice model with an easy-axis anisotropy using the extended dynamical mean field theory. We derive results in real frequency by using the bosonic numerical renormalization group (BNRG) method and compare them with quantum Monte Carlo results in Matsubara frequency. The BNRG results show a logarithmic divergence in the critical local spin susceptibility, signaling a destruction of Kondo screening. The T=0 transition is consistent with being second order. The BNRG results also display some subtle features; we identify their origin and suggest means for further microscopic studies.     

Fluorinated Azobenzenes Switchable with Red Light

Molecular photoswitches triggered with red or NIR light are optimal for photomodulation of complex biological systems, including efficient penetration of the human body for therapeutic purposes (“therapeutic window”). Yet, they are rarely reported, and even more rarely functional under aqueous conditions. In this work, fluorinated azobenzenes are shown to exhibit efficient E→Z photoisomerization with red light (PSS_660nm >75 % Z) upon conjugation with unsaturated substituents. Initially demonstrated for aldehyde groups, this effect was also observed in a more complex structure by incorporating the chromophore into a cyclic dipeptide with propensity for self-assembly. Under physiological conditions, the latter molecule formed a supramolecular material that reversibly changed its viscosity upon irradiation with red light. Our observation can lead to design of new photopharmacology agents or phototriggered materials for in vivo use.     

New engineering polymers for blow-moulding

The combination of using high performance flexible engineering polymers and their processing by blow moulding technology allows traditional rubber and rubber-metal composite parts to be replaced to obtain improved performance, lower cost and greater design freedom. Two examples of automobile applications are detailed to support this concept - constant velocity joint boots and engine air ducting.     

Gas hydrate single-crystal structure analyses

The first single-crystal diffraction studies on methane, propane, methane/propane, and adamantane gas hydrates SI, SII, and SH have been performed. To circumvent the problem of very slow crystal growth, a novel technique of in situ cocrystallization of gases and liquids resulting in oligocrystalline material in a capillary has been developed. With special data treatment, termed oligo diffractometry, structural data of the gas hydrates of methane, acetylene, propane, a propane/ethanol/methane-mixture and an adamantane/methane-mixture were obtained. Cell parameters are in accord with reported values. Host network and guest are subject to extensive disorder, reducing the reliability of structural information. It was found that most cages are fully occupied by a guest molecule with the exception of the dodecahedral cage in the acetylene hydrate which is only filled to 60%. For adamantane in the icosahedral cage a disordered model is proposed.     

Beta decay of 101Sn

The β decay of the very neutron-deficient isotope ¹⁰¹Sn was studied at the GSI on-line mass separator using silicon detectors for recording charged particles and germanium detectors for γ-ray spectroscopy. Based on the β-delayed proton data the production cross-section of ¹⁰¹Sn in the ⁵⁰Cr + ⁵⁸Ni fusion-evaporation reaction was determined to be about 60nb. The half-life of ¹⁰¹Sn was measured to be 1.9(3)s. For the first time β-delayed γ-rays of ¹⁰¹Sn were tentatively identified, yielding weak evidence for a cascade of 352 and 1065keV transitions in ¹⁰¹In. The results for the ¹⁰¹Sn decay as well as those from previous work on the ¹⁰³Sn decay are discussed by comparing them to predictions obtained from shell model calculations employing a new interaction in the ⁸⁸Sr to ¹³²Sn model space.