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  • 1
    ISSN: 1434-1948
    Keywords: Metal complexes ; Organic conductors ; Selenium ; Magnetic properties ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Novel metal complexes (R4N)[Ni(ddds)2] (R = Me, Et and nBu, ddds = 5,6-dihydro-1,4-dithiin-2,3-diselenolate) have been prepared and their crystal structures determined. The intraligand Se-Se distance is longer than that between the inner sulfur atoms of the five-member ring of the M(dddt)2- sulfur analogue and is almost equal to the S-S distance in the six-member ring. Consequently, two-dimensional intermolecular close contacts are expected, and observed in Ni(ddds)2 complexes. The neutral Ni(ddds)2 species was obtained by electrochemical oxidation from the monoanionic (nBu4N)[Ni(ddds)2] complex. X-Ray crystal structure analyses of this neutral species show that two Ni(ddds)2 are connected by the two Ni-Se bonds. Thus, the Ni(ddds)2entities form [Ni(ddds)2]2dimers which are arranged face-to-face and rotated by about 90° with respect to each other. The electrochemical behavior of (nBu4N)[Ni(ddds)2] indicates the possible formation of cation-radical species. The room temperature magnetic susceptibility measurements showed that the (R4N)[Ni(ddds)2] complexes are paramagnetic with μeff = 1.77-1.83 μB, corresponding to one unpaired electron per molecular formula. The temperature dependence of the magnetic susceptibility of (Et4N)[Ni(ddds)2] is indicative of weak long-range antiferromagnetic ordering below 9 K. The dimerization in [Ni(ddds)2]2results in a strong antiferromagnetic spin coupling within the dimer, and explain the non magnetic state observed for this compound.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1434-193X
    Keywords: Tetrathiafulvalenes ; Charge transfer ; UV/Vis spectroscopy ; Cyclic voltammetry ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---4-[2-tetrathiafulvalenyl-ethenyl]pyridine (1) has been prepared from a Wittig reaction between formyltetrathiafulvalene and 4-picolyltriphenylphosphonium chloride hydrochloride. Conversion of the pyridine moiety of 1 by reaction with methyl iodide leads to 4-[2-tetrathiafulvalenyl-ethenyl]-1-methylpyridinium iodide (2a). Neutralization of 1 with a large excess of L-tartaric acid affords 4-[2-tetrathiafulvalenyl-ethenyl]-1-methylpyridinium hydrogen tartrate (3). These TTF-π-spacer-acceptor compounds have been characterized by elemental analysis, and IR and 1H NMR spectroscopy. The crystal structure of 2a has been determined by X-ray diffraction. The cation is essentially planar. Examination of the bond lengths in 2a, UV/Vis spectra and CV data, and calculations indicate that an intramolecular charge transfer occurs in the studied compounds, although it is rather limited, and larger in 2a and 3 than in 1.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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