Magneto-structural relationships in a series of dinuclear oxalato-bridged (diphenyldipyrazolylmethane)copper(II) complexes

A series of oxalato-bridged dinuclear copper(II) complexes of the general formula [Cu2(Pz2CPh2)2(X)2(mu-C2O4)] (X = Cl- (1), NO3(-) (2), ClO4(-) (3); Pz2CPh2 = diphenyldipyrazolylmethane) or [Cu2(Pz(3m)2CPh2)2(H2O)2(mu-C2O4)](NO3)2 x H2O (4) (Pz(3m)2CPh2 = diphenylbis(3-methylpyrazolyl)methane) was synthesized where the axial ligand was systematically varied to study its effect on structure and magnetic coupling. The structures of compounds 1, 2, and 4 have been elucidated by single-crystal X-ray diffraction. [Cu2(Pz2CPh2)2(Cl)2(mu-C2O4)] and [Cu2(Pz2CPh2)2(NO3)2(mu-C2O4)] are isostructural and crystallize in the triclinic system, space group P, Z = 2, with a = 8.6155(8) A, b = 10.1435(9) A, c = 11.3612(11) A, alpha = 95.535(2) degrees, beta = 110.303(2) degrees, and gamma = 106.111(2) degrees for 1 and with a = 8.863(7) A, b = 10.241(9) A, c = 11.425(10) A, alpha = 98.985(14) degrees, beta = 110.449(13) degrees, and gamma = 103.664(14) degrees for 2. [Cu2(Pz(3m)2CPh2)2(H2O)2(mu-C2O4)] x NO3 x H2O crystallizes in the monoclinic system, space group C2/c, Z = 4, with a = 23.4588(14) A, b = 8.8568(5) A, c = 21.7818(13) A, alpha = gamma = 90 degrees, and beta = 100.8890(10) degrees. Variable-temperature magnetic susceptibility studies indicate that all four compounds are strongly antiferromagnetically coupled (2J/k = -364, -344 cm(-1) (2), -424 cm(-1) (3), and -378 cm(-1) (4)). Magnetic and EPR results are discussed with respect to structural parameters to explore possible magneto-structural correlations.     

Cover Picture

The cover picture shows, on the right, a field of 25 copper clusters on a gold(111) electrode surface. The clusters were deposited from solution with the tip of a scanning-tunneling microscope. The clusters were first isolated from the electrolyte onto the tip and selectively transferred onto the surface by the tip being in proximity to the substrate (see under for a sketch of the mechanism). The metal clusters are composed or approximately 100 atoms and are unexpectedly stable against anodic dissolution. As the picture on the left illustrates, the clusters also remain stable for a long time against a positive Nernst potential. In the background, one sees a section of the gold surface with the copper clusters.[ Cover Picture ]     

Antiproton-proton annihilation at rest intoπ + π − η ′ andπ + π − η from atomicS andP states

We have measured the branching ratios for \(\bar pp\) annihilation at rest intoπ ⁺ π ^? η andπ ⁺ π ^? η′ in hydrogen gas in two data samples that have different fractions ofS-wave andP-wave initial states. The branching ratios are derived from a comparison with the topological branching ratio for \(\bar pp\) annihilations into four charged pions of (49±4)% and the branching ratio intoπ ⁺ π ^? π ⁺ π ^? π ⁰ of (18.7±1.6)%. We find a significant reduction of the branching ratios fromP-states for \(\bar pp \to \pi ^ + \pi ^ - \eta \) andπ ⁺ π ^? η′ in comparison toS-state annihilation. $$\begin{gathered} BR(S - wave \to \pi ^ + \pi ^ - \eta ) = (13.7 \pm 1.46) \cdot 10^{ - 3} \hfill \\ BR(P - wave \to \pi ^ + \pi ^ - \eta ) = (3.35 \pm 0.84) \cdot 10^{ - 3} \hfill \\ BR(S - wave \to \pi ^ + \pi ^ - \eta ') = (3.46 \pm 0.67) \cdot 10^{ - 3} \hfill \\ BR(P - wave \to \pi ^ + \pi ^ - \eta ') = (0.61 \pm 0.33) \cdot 10^{ - 3} . \hfill \\ \end{gathered} $$ In a partial wave analysis of theπ ⁺ π ^? η Dalitz plot we find the following contributions: Phase space, \(a_2^ + (1320)\pi ^ \mp \) ,ηρ⁰ andf ₂(1270)η: $$\begin{gathered} BR(S - wave \to \pi ^ + \pi ^ - \eta PS) = (6.31 \pm 1.22) \cdot 10^{ - 3} \hfill \\ BR(P - wave \to \pi ^ + \pi ^ - \eta PS) = (0.47 \pm 0.26) \cdot 10^{ - 3} \hfill \\ BR(^1 S_0 \to a_2^ \pm (1320)\pi ^ \mp ) = (2.59 \pm 0.73) \cdot 10^{ - 3} \hfill \\ BR(^3 S_1 \to a_2^ \pm (1320)\pi ^ \mp ) = (1.31 \pm 0.48) \cdot 10^{ - 3} \hfill \\ BR(P - wave \to a_2^ \pm (1320)\pi ^ \mp ) = (1.31 \pm 0.69) \cdot 10^{ - 3} \hfill \\ BR(^3 S_1 \to \rho \eta ) = (3.29 \pm 0.90) \cdot 10^{ - 3} \hfill \\ BR(^1 P_1 \to \rho \eta ) = (0.94 \pm 0.53) \cdot 10^{ - 3} \hfill \\ BR(^1 S_0 \to f_2 (1270)\eta ) = (0.083 \pm 0.086) \cdot 10^{ - 3} \hfill \\ BR(P - wave \to f_2 (1270)\eta ) = (0.64 \pm 0.26) \cdot 10^{ - 3} . \hfill \\ \end{gathered} $$ We find a 2 σ effect for the reaction \(\bar pp \to a_0^ \pm (980)\pi ^ \mp \) , \(a_0^ \pm \to \eta \pi ^ \pm \) , with a branching ratio of (0.13±0.07)·10^?3. For η' production we give a branching ratio of \(\bar pp \to \rho \eta '\) of (1.81±0.44)·10^?3 from³ S ₁. We estmate a contribution of about 0.3·10^?3 for ρη' fromP-states. The ratio of ρη and ρη' rpoduction is used to test the validity of the quark line rule. In theπ ⁺ π ^? π ⁺ π ^? γ final state we do not observe the reaction \(\bar pp \to \pi ^ + \pi ^ - \omega \) , ω→π ⁺ π ^? λ and derive an upper limit of 3·10^?3 for decay modeω→π ⁺ π ^? λ.     

Substituent effect to prevent autoxidation and improve spectral stability in blue light-emitting polyfluorenes

A group of fluorene-based polymers, PF-1SOR and PF-2SOR, were synthesized and characterized as blue light-emitting materials. PF-1SOR and PF-2SOR displayed nematic liquid crystalline mesophase in films cast from solution. Compared with conventional polyfluorene, PF-1SOR and PF-2SOR display blue-shifted UV absorption and structureless blue fluorescence. The photoluminescence spectra of PF-1SOR and PF-2SOR were found insensitive against thermal treatment in air up to 200 degrees C and the blue electroluminescence in their light-emitting devices was independent of the driving voltage. Compared to the conventional polyfluorenes, the improved spectral stability of these polymers is attributed to the anti-oxidization effect of (3,5-di(tert-butyl)phenoxy)sulfonyl side groups attached to the backbone.     

Synthesen von Heterocyclen. 19. Mitt.

Zusammenfassung Bei der Kondensation von o-Hydroxy-acetophenonen (I–VI) mit Benzylmalonsäure-bis-(2,4-dichlorphenol)-ester VII entstehen über Derivate des 4-Hydroxy-6-phenyl-2-pyrons (z. B. IX) solche des 5,8-Dioxo-2,3-benzo-1,4,7-dipyranopyrans (XI–XVII). Mit unsubstituiertem Malonsäure-bis-(2,4-dichlorphenol)-ester XXI reagieren diese (I, V und VI) vermutlich zu Estern der Cumarin-3-carbonsäuren XXII–XXIV.Aus o-Hydroxy-propiophenonen und dem Ester XXI bilden sich dagegen Verbindungen von Typ des Pyrono-pyrons (XXV und XXVI).Herrn Prof. Dr.M. Rebek in Freundschaft und Verehrung zum 70. Geburtstag gewidmet.