The electron impact fragmentation of 3- and 4-styrylpyridazine

The electron impact mass spectrometric fragmentation of trans-3- and trans-4-styrylpyridazine is reported in detail, including a comparison with other aza-stilbenes. With regard to a distinction between the two isomeric styrylpyridazines, the intensity ratio of the M⁺ and [M-1]⁺ ions, the general degree of fragmentation and the elimination pathways of nitrogen proved to be most characteristic.     

Intrazelluläre Lokalisierung und Funktion von NADPH-Cytochromc-Reduktase in Saccharomyces cerevisiae

Zusammenfassung Das Flavoprotein NADPH-Cytochromc-Reduktase aus Hefe ist im Gegensatz zu bisherigen Anschauungen kein Enzym der mitochondralen Atmungskette, sondern an bisher unbekannte subzelluläre Partikel gebunden, die nach Homogenisieren der Hefezellen von den Mitochondrien abgetrennt werden können. Die Beteiligung von Cytochromb ₂ oder einer Transhydrogenase-reaktion an der Elektronenübertragung von NADPH auf Cytochromc in einem Hefehomogenat konnte ausgeschlossen werden. Die Natur der neuen Hefepartikel sowie die physiologische Funktion des Enzyms NADPH-Cytochromc-Reduktase werden diskutiert.Abkürzungen NADPH reduziertes Nikotinamid-adenin-dinukleotidphosphat - NADH reduziertes Nikotinamid-adenin-dinukleotid - Tris Tris-(hydroxymethyl)aminomethan - BAL 1,2-Dimercapto-3-hydroxypropan - RNase Ribonuklease - ATPase Adenosintriphosphatase - EDTA Äthylendiamintetraessigsäure Mit 2 Abbildungen     

Synthesen und Reaktionen von Pyridazinderivaten, 11. Mitt.: 5-Acyl-4-pyridazincarbonsäurrester als „key intermediates” für 4-Acylpyridazine und 4-Alkyl-bzw. 4-Arylpyridazino[4,5-d]pyridazin-1 (2H) one

A convenient general method of preparing 4-acylpyridazines (4) is reported. It involves homolytic acylation of ethyl-4-pyridazinecarboxylate yielding ethyl-5-acyl-4-pyridazinecarboxylates (2) which easily can be converted to4 by alkaline hydrolysis followed by decarboxylation. The hitherto unknown pyridazino[4,5-d]pyridazine-1 (2H) ones bearing an alkyl- or arylsubstituent on C-4 (5a-g) were prepared in quantitative yields by reaction of2 with hydrazine.

10. Mitt.:G. Heinisch, A. Jentzsch undI. Kirchner, Tetrahedron Lett.1978, 619.     

Impact of Transition Metal Substituents on Polysilane Properties: Iron versus Ruthenium

Summary. The previously unknown ruthenio disilanes Rp–Si₂Me₄–C₆H₄X (Rp = η⁵-C₅H₅Ru(CO)₂; X = H, Br, –CHO, CH=C(CN)₂) were synthesized from ClSi₂Me₄C₆H₄X (X = H, Br) and Rp⁻ using conventional chemical methods. Trends in the UV/Vis absorption spectra indicate strong electronic coupling within the Rp–Si–Si–C_aryl fragment and, therefore, closely resemble the ones observed for the corresponding iron complexes. The four compounds however, were shown to be less sensitive towards UV irradiation. The crystal structure of Rp–Si₂Me₄–C₆H₄CH=C(CN)₂ was determined by X-ray diffraction and exhibits an all-trans-array of the Ru–Si–Si–C_aryl moiety, what is a basic requirement for optimal through-bond interaction.     

Theoretical evidence for the singlet diradical character of square planar nickel complexes containing two o-semiquinonato type ligands

Density functional theory and complete active space self-consistent field computations are applied to elucidate the singlet diradical character of square planar, diamagnetic nickel complexes that contain two bidentate ligands derived from o-catecholates, o-phenylenediamines, o-benzodithiolates, o-aminophenolates, and o-aminothiophenolates. In the density functional framework, the singlet diradical character is discussed within the broken symmetry formalism. The singlet-triplet energy gaps, the energy gained from symmetry breaking, the spin distribution in the lowest triplet state, and the form of the magnetic orbitals are applied as indicators for the singlet diradical character. Moreover, a new index for the diradical character is proposed that is based on symmetry breaking. All symmetry breaking criteria show that the complexes obtained from o-catecholates and o-benzodithiolates have the largest and the smallest singlet diradical character, respectively. The singlet diradical character should be intermediate for the complexes derived from o-phenylenediamines, o-aminophenolates, and o-aminothiophenolates. The diradical character of all complexes suggests the presence of Ni(II) central atoms. This is also indicated by the d-populations computed by means of the natural population analysis.     

Longitudinal relaxation of muonium in Ge and GaAs

Longitudinal-field muon-spin depolarization rates in high-purityGe and semiinsulatingGaAs are reported and compared to similar data for intrinsicSi. Depolarization onset temperatures provide a comparison of charge carrier concentrations leading to rapid charge exchange and a shift in the onset, for n-typeGaAs verifies anelectron process. The temperature dependence of the low-field rate constants imply more complicated dynamics inGe than observed earlier inSi. Features near 750K inGaAsTe appear consistent with dissociation of aMu-Te pair.This work was supported by the US National Science Foundation (DMR-8917639 [TLE, BH]), the Science and Engineering Research Council of the UK (EAD, AS, SFJC), the Robert A. Welch Foundation (D-1053 [RLL], and C-1048 [TLE]), and a NATO Collaborative Research Grant (RLL, SFJC, RCD, CS). We wish to thank D.A. Vanderwater of Hewlett Packard for providing theGaAsTe sample.     

RF-μSR study of muonium charge states and dynamics in Si

The radio frequencySR technique developed at TRIUMF was used to measure the temperature dependence of the diamagnetic muon, Mu, and Mu^* amplitudes in silicon between 10 K and 500 K. Six samples doped with phosphorus (n-type) and boron (p-type) in the concentration range 10¹¹ to 10¹⁵ cm^–3 were studied. In pure Si a very good fit over the whole temperature range is obtained from a model that includes the ionization of Mu^* and Mu to a bond centered ⁺ followed at high temperature by charge exchange involving Mu.     

Structural Projections on JBW*-Triples

A linear projection R on a Jordan*-triple A is said to be structuralprovided that, for all elements a, b and c in A, the equality{Rab Rc} = R{a Rbc} holds. A subtriple B of A is said to becomplemented if A = B + Ker(B), where Ker(B) = {aA: {B a B}= 0}. It is shown that a subtriple of a JBW*-triple is complementedif and only if it is the range of a structural projection. A weak* closed subspace B of the dual E* of a Banach space Eis said to be an N*-ideal if every weak* continuous linear functionalon B has a norm preserving extension to a weak* continuous linearfunctional on E* and the set of elements in E which attain theirnorm on the unit ball in B is a subspace of E. It is shown thata subtriple of a JBW*-triple A is complemented if and only ifit is an N*-ideal, from which it follows that complemented subtriplesof A are weak* closed, and structural projections on A are weak*continuous and norm non-increasing. It is also shown that everyN*-ideal in A possesses a triple product with respect to whichit is a JBW*-triple which is isomorphic to a complemented subtripleof A.