Nanostructure and thermoelectric properties of ReSi 2+/-x thin films

Anomalies in the nanostructure evolution of ReSi(2+/-x) thin films have proved to be of large interest in connection with their thermoelectric properties. By means of electron microscopic methods the correlation between structural properties and transport behaviour has been studied. The short-range order of the amorphous state was characterised by reduced density functions calculated from diffuse electron diffraction diagram and is found to correlate with the temperature dependence of the electrical resistance. The crystallisation process observed in situ in the transmission electron microscope starts with the formation of relatively large ReSi(1.75) grains (up to 100 nm). In later stages, only smaller grains are growing. This leads to a decrease in the mean grain size and to the increase of the nanocrystalline volume fraction during the heat treatment. This behaviour allows the investigation of the thermopower as function of the nanocrystalline volume fraction. Thus, at a nanocrystalline content of about 35% the thermopower exhibits a maximum in accordance with calculations.     

Homoleptische Zinkamide: Der Übergang zu monomeren Molekülen

Homoleptic Zinc Amides: Transition to Monomeric Molecules Zinc chloride reacts with the lithium salts of the bulky secondary amines HN(i-Bu)₂ and HN(t-Bu)₂ to form the corresponding homoleptic zinc compounds {Zn[N(i-Bu)₂]₂}₂ ( 1 ) and Zn[N(t-Bu)₂]₂ ( 2 ). The NMR spectroscopic and mass spectrometric results as well as the molecular weight determinations and X-ray diffraction data are consistent with a dimeric structure of 1 and a monomeric structure of 2 in the gas phase, in solution and in the solid state.     

Cation-induced charge-transfer absorptions of oligooxa[n.n]Paracyclophane quinhydrones

Intramolecular [n.n]paracyclophane quinhydrones with two oligo= oxaalkylene bridges 2a–e (m = 0,1,2,3 and 4, resp.) have been synthesized. The selective double complexation of these compounds with metal cations of suitable size (e.g. 7) is indicated by remarkable enhancements of the intensity of charge-transfer absorptions.     

Photoelektronenspektroskopische untersuchung von tris(trimethylelement(IV)aminen, -phosphinen, -arsinen und -stibinen

The PE spectra of [(CH₃)₃Sn]₃N, [(CH₃)₃E]₃P (E = C, Si, Sn), [(CH₃)₃Si]₃As and [(CH₃)₃E]₃Sb (E = C, S, Ge, Sn) are analyzed. The constant level of the ionization potentials of the n-hybrid orbitals of N, P, As, and Sb, together with changes in the hybridization and interactions with ligand MO's is discussed by qualitative MO investigations.     

Metallorganische verbindungen der lanthanoide : LXX. Bis(cyclopentadienyl)seltenerdkomplexe: Synthese und röntgen-strukturanalyse von dem intramolekular stabilisierten lutetiumalkyl Cp2 Me2 und dem monomeren basenfreien yttriumcarboxylat Cp2Y[η-O2C(CH2)3NMe2]

Metathesis of LuCl₃, NaCp and Li(CH₂)₃NMe₂ in the molar ratio 1:2:1 affords the lutetium alkyl species Cp₂ Me₂ (1); analogous reaction of LuCl₃, NaMeC₅H₄ and LiCH₂CH(Me)-CH₂NMe₂ generates the corresponding complex (MeC₅H₄)₂ Me₂] (2). Treatment of YCl₃ with two equivalents of NaCp and one equivalent of Li(CH)₃NMe₂ yields, in the presence of CO₂, the yttrium carboxylate Cp₂Y[η²-O₂C(CH₂)₃NMe₂ (3). Mass spectrometrical studies of the solvent-free rare earth triflates [Cp₂Ln(OSO₂CF₃)]₂ (Ln = Sc (4), Lu (5)) have shown them to be dimeric. The crystal structures of 1 and 3 were determined by X-ray diffraction methods. 1 crystallizes in the monoclinic space group P2₁ (No. 4) with the unit-cell parameters a 657.0(4), b 1386.7(8), c 803.5(3) pm, β 106.64(5)°, V 704(1) × 10⁻³⁰ m³ and Z = 2. The structure was solved on the basis of 1094 observed reflections with F₀ ≥ 3σ(F₀) and refined to a final R value of 0.0483. With the short Lu---N bond length of 237(1) pm the molecular structure of 1 exhibits an intramolecular N → Lu coordination. The crystals of 3 are triclinic, space group P (No. 2), with a 1078.2(6), b 1533.0(9), c 1020.3(8) pm, α 109.47(6), β 82.75(6), γ 88.99(5)°, V 1574(2)×10⁻³⁰ m³ and Z = 4. Least-squares refinement of the model based on 1659 observed reflections converged to R = 0.093 (F₀ ≥ 5σ(F₀)). The structural data of 3 feature a monomer with a chelating carboxylate group. The long Y---N distance (499 pm) excludes any intramolecular N---Y interactions.     

Über Reaktionen mit Betain, 24. Mitt.: Über Umsetzungen von Trimethylammoniumessigsäurebetain mit reaktiven Halogenverbindungen

Summary Diethyl bromomalonate and bromoacetonitrile, respectively, react with trimethylammonium acetic acid betaine in ethanol to give diethyl tartronate and glycolic acid nitrile, respectively. By analogy, ethyl -chloroacetonate and ethyl bromopyruvate yield the respective hydroxy derivatives which were identified by their osazones2 and3. Under the same experimental conditions, mesoxalic acid and its dimethyl ester, respectively, are formed from dibromo malonic acid and its dimethyl ester and were characterized by their known hydrazones8 and9.

Herrn o. Prof. Mag. pharm. Dr. H. Junek, Karl-Franzens-Universität Graz, zur Vollendung des 60. Lebensjahres mit besten Wünschen gewidmet     

Die Struktur einer stabilen dipolaren Verbindung aus 2,2-Dimethyl-3-dimethylamino-2H-azirin und Benzoylisothiocyanat. Vorläufige Mitteilung

Structure of a Stable Dipolar Compound from 2,2-Dimethyl-3-dimethylamino-2H-azirine and Benzoylisothiocyanate. Benzoylisothiocyanate and 2,2-dimethyl-3-dimethylamino-2H-azirine ( 1 ) react to given the dipolar compound 4,4-dimethyl-2-thiazolin-5-dimethylimminium-2-benzcarboxamidate ( 2 ), whose structure has been proved by X-ray analysis. Compound 2 , upon addition of water, yields the thiourea derivative 3 , whereas by acid catalyzed hydrolysis the thiazolinone derivative 4 is formed. The dipolar structure 2 is also existent in organic solvents like dimethylsulfoxide or chloroform.     

Zur Chemie der Pyrrolpigmente, 62. Mitt.

Sixteen diastereomeric 2,3-dihydrobilatrienes-abc substituted in position 3 with various chiral ligands, seven chiral derivatives of a 2,3-dihydrobilatriene-abc-12-propionic acid and a chiral derivative of a 8,12-bilatriene-abc-dipropionic acid were prepared. The chiroptical properties (CD) of these compounds were used as a monitor for the conformational influence of the various ligands. Therefrom it could be deduced that steric effects play a minor role in determining the topology of the chromophore. On the contrary, dipole-dipole interactions of the various partial moments of bile pigments and of the attached ligands crucially influence the conformational situation of the chromophore. This fact may be significant for the stabilization of certain chromophore conformations in biliproteids.

Herrn Prof. Dr.K. Winsauer zum 60. Geburtstag gewidmet.