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Schlagwörter:
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Zusammenfassung:
Partially deuterated and I3C-labeled bis(bipheny1enyl)propenyl radicals have been studied by means of ESR and
ENDOR spectroscopy. Isotropic and anisotropic hyperfine contributions could be determined from measurements in isotropic
solutions and in nematic and smectic phases of liquid crystals. Assignments of hyperfine coupling constants and shifts to molecular
positions were achieved. Conclusions concerning molecular structure, e.g., twist angles, could be drawn by relating the experimental
data to quantum mechanical calculations. These results could be confirmed by taking account of the I3C hyperfine
shifts determined by ESR and ENDOR experiments. A marked isotope effect on the P-proton hyperfine coupling could
be observed when replacing 1H by 2H in the biphenylenyl moieties. The essential feature of the 2H ENDOR measurements in
liquid crystals is the detection of deuterium quadrupole splittings. The relaxation behavior of the different magnetic nuclei is
discussed. A novel multinuclear ENDOR standard for checking the engineering design of a liquid-phase ENDOR spectrometer is proposed.
