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  • Copper polysulfide  (1)
  • Key words Ab initio  (1)
  • UV/visible spectroscopy  (1)
  • 1
    ISSN: 1572-8862
    Keywords: Copper polysulfide ; X-ray crystal structure ; infrared spectroscopy ; UV/visible spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The title compound, Cu4S10(4-methylpyridine)4 · 4-methylpyridine was prepared by three different reactions: the oxidation of copper power by sulfur and the reaction of copper (I) sulfide (or CuBr-SMe2) with cues sulfur, both in the coordinating solvent, 4-methylpyridine. Red crystals of the compound obtained by layering with hexans were subjected to single crystal X-ray diffraction. The structure was refined toR=0.026 and R w =0.036 in a space groupP1bar (No. 2), withZ=2,a=13.983 (2) A,b=15.384( 2) Å,c=9.660 (1) Å, α = 93.87 (1)°,β=93.38 =γ=(1)°,V=2037.9 (9) Å3. The commpound has approximate S4 symmetry and consists of two pentasuffide chains linking four Cu(I) ions, each with a coordinating 2-methylpyridine. The infrared spectrum was dominated by absorption due to coodinated 4-methylpyridine with several low-energy peaks attributable to S-S stretches, which were also observed by Raman spectroscopy. A featureless electronic absorption spectrum yielded a single peak in the mar ultraviolet upon computer enhancement (λ=334 nm, ε = 10,000), most likely an intraligand transition. Cyclic voltammetry indicates that the polysulfide complex undergoes irreversible oxidation and reduction at +0.04 and −0.34 V vs. SCR respectively, at NS K in 4-methylpyridine when swept at 20 mV/sec. The electrochemical behavior was unvaried even at sweep rates as high as 100 V/sec.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1327
    Keywords: Key words Ab initio ; Silver ; Nucleobase ; Cytosine ; Adenine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract  Ab initio calculations have been carried out to characterize the structure and energetics of a silver(I) complex with the cytosine-adenine DNA base pair and an aqua ligand in the coordination sphere of Ag. In addition, we have also studied analogous complexes with Cu(I) and Au(I), and structures in which adenine has been replaced by purine in order to investigate the structural role of the adenine amino group. The calculations revealed that all metal-modified structures are dominated by the metal-base interactions, while the water-metal ion interaction and many-body interligand repulsion are less important contributions. Nevertheless, the structural role of the water molecule in the complex is quite apparent and in agreement with an earlier crystallographic study. The metal-modified base pairs exhibit large conformational flexibility toward out-of-plane motions (propeller twist and buckle), comparable or, in some cases, even larger than that observed in the base pairs without metal ions. All structures have been optimized within the Hartree-Fock approximation, while interaction energies were evaluated with the inclusion of electron correlation.
    Type of Medium: Electronic Resource
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