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>EPR and ENDOR of triplet state diphenylhyphen;h10in diphenylhyphen;d10single crystals. Molecule conformation and spin distribution
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EPR and ENDOR of triplet state diphenylhyphen;h10in diphenylhyphen;d10single crystals. Molecule conformation and spin distribution
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机译：EPR and ENDOR of triplet state diphenylhyphen;h10in diphenylhyphen;d10single crystals. Molecule conformation and spin distribution
The results of EPR and ENDOR spectroscopic measurements for the lowest energy triplet state of diphenylhyphen;h10molecules dilutely substituted for host molecules in diphenylhyphen;d10single crystals at 1.9thinsp;deg;K are reported. These measurements show clearly that the triplet state molecules do not have the center of symmetry possessed by the host molecules, with their two parallel ring planes, in the crystal at room temperature. However, the host molecules have lost their center of symmetry at low temperature by a twisting of the two rings about the central interhyphen;ring bond, whereas the triplet state molecules at 1.9thinsp;deg;K are found to have parallel ring planes and have not lost the center as a result of such a twisting. The reported results also show that although the nuclear coordinates are very close (relative to the precision of the ENDOR measurements) to those required by an ideal molecularD2hsymmetry, nevertheless the principal axes of the fine structure interaction are rotated in the plane of the molecule by the relatively large angle, 0.046pgr;(8.3deg;), from the directions of the approximate molecular symmetry axes. This last fact removed the previously reported discrepancy between the value of the angle between the long molecular axes of the two translationally inequivalent molecules per unit cell determined by xhyphen;ray diffraction and that determined by EPR under the assumption that the fine structure principal axes and the molecular symmetry axes were coincident. This lack of coincidence arises from the large deviations of the spin distribution, from that demanded byD2hsymmetry, produced by the very small deviations of the nuclear coordinates from the ideal symmetry. The spin distribution has been measured in these experiments and the spin densities reported here are shown to be in agreement with the preceding statements.
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