Distortion isomerism of Cu(II) chloride adducts with bis(2-benzimidazolyl)ethane. Synthesis, characterization, X-ray structures and spectroscopy of four different isomers

Metals in Catalysis, Biomimetics & Inorganic Material

Synthesis, crystal structure and spectroscopy of catena-poly-bis(azido-N1,N1)(2-Aminopyrimidine)Copper(II)

The compound [Cu(ampym)(l1,1-N3)2]n (ampym = 2-aminopyrimidine) has been synthesized and characterized by X-ray crystallography and infrared spectroscopy. In addition, Ligand Field and powder EPR measurements have been performed. The structure is solved in space group P21/c with a = 7.303(2), b = 19.716(4), c = 5.949(1) A˚ , b = 98.17(3), V = 847.9(3) A˚ 3 , Z = 2 with final R = 0.0382. The coordination geometry around the Cu(II) ion is distorted square pyramidal, with four nitrogen atoms of four bridging azido anions in the basal plane with Cu–N distances that range from 1.998(3) to 2.069(3) A˚ . The apical position is occupied by a nitrogen atom of the ampym molecule at a Cu–N distance of 2.169(3) A˚ . The trans-basal angles are 165.7(1) and 143.9(1). Weak hydrogen bonding is observed between the two amine hydrogen atoms and nitrogen of an azide anion and the pyrimidine-ring nitrogen atom of a neighbouring molecule (NN distances 3.174(5), 3.106(4) A˚ ). These last hydrogen bonds (N7N3) are forming so-called ‘‘WatsonCrick type’’ hydrogen bonds. In the infrared the vibrations of the coordinated azide anion are observed at 2,062, 1,273 and 655 cm-1 , while the Cu–N vibrations are observed at 370 and 224 cm-1 . Ligand-field and EPR spectra are uneventful and give spectral parameters expected in the range for such Cu(II) compounds. Magnetic susceptibility measurements reveal a weak antiferromagnetic interaction between the Cu(II) ions.Metals in Catalysis, Biomimetics & Inorganic Material

Cu(II) Compounds with Pyrimidine-Based Chelating Ligands, Bridged by a Flexible Alkyl Spacer: Synthesis, Characterisation and X-Ray Structures of Methoxide-Bridged Dinuclear-Based Species

Metals in Catalysis, Biomimetics & Inorganic Material

Red and Blue Compounds Formed from Copper(II) Bromide and the Ligand 7-Isobutyl-5-methyl-[1,2,4]triazolo [1,5-a]pyrimidine: Synthesis, Spectroscopy and Single-Crystal Structures

Metals in Catalysis, Biomimetics & Inorganic Material

Horizontal Branch Stars: The Interplay between Observations and Theory, and Insights into the Formation of the Galaxy

We review HB stars in a broad astrophysical context, including both variable and non-variable stars. A reassessment of the Oosterhoff dichotomy is presented, which provides unprecedented detail regarding its origin and systematics. We show that the Oosterhoff dichotomy and the distribution of globular clusters (GCs) in the HB morphology-metallicity plane both exclude, with high statistical significance, the possibility that the Galactic halo may have formed from the accretion of dwarf galaxies resembling present-day Milky Way satellites such as Fornax, Sagittarius, and the LMC. A rediscussion of the second-parameter problem is presented. A technique is proposed to estimate the HB types of extragalactic GCs on the basis of integrated far-UV photometry. The relationship between the absolute V magnitude of the HB at the RR Lyrae level and metallicity, as obtained on the basis of trigonometric parallax measurements for the star RR Lyrae, is also revisited, giving a distance modulus to the LMC of (m-M)_0 = 18.44+/-0.11. RR Lyrae period change rates are studied. Finally, the conductive opacities used in evolutionary calculations of low-mass stars are investigated. [ABRIDGED]Comment: 56 pages, 22 figures. Invited review, to appear in Astrophysics and Space Scienc

Spiegelinformatie omtrent gebruik van TNFα-remmers in de Nederlandse reumatologie (mei 2011).

Item does not contain fulltex