No abstract

No abstract

No abstract

elution with 5 mM sodium phosphate buffer on a phosphate-containing Dowex 1-X2 column. The free trisaccharide 3, whose interglycosidic linkages were confirmed by i H-NMR spectroscopy,"] was thereby obtained directly on a 50-pmol scale (yield: 31 mg, 52%).

No abstract

Studies of a series of substituted benzo-, naphtho-, anthra-and phenanthrene-semiquinones, benzil semidione and Wurster's blue perchlorate by ENDOR spectroscopy in liquid crystalline solutions are reported. Sufficient solubility of the radical anions is achieved by using lipophilic counter ions such as benzyltrimethylammonium. The effects of ion pairing were investigated, particularly in the case of benzil semidione, which can adopt cis or trans configurations. The anisotropic hyperfine shifts observed in nematic or smectic phases are interpreted by means of calculated dipolar hyperfine tensors. A detailed picture of the alignment of the radical ions in liquid crystalline solvents is obtained. The calculated hyperfine tensors are checked for consistency with experiment, and in some cases compared with measurements in solid solution.

No abstract

Radical cations of a series of a-methyl-substituted bi-, ter-and quaterthiophenes were investigated by EPR and, in part, ENDOR spectroscopy. In the case of terthiophenes, the electronic and steric effects of methyl substituents were studied. The experimentally determined spin density distributions were rationalized by means of semiempirical quantum-mechanical calculations (MNDO, PM3, RHF-INDO/SP). Sterically noo-hindered oligothiop hene radical cations are planar and form mixtures of cis and trans conformers, whereas uniform species were observed in the case of sterically hindered, non-planar radical cations.