Spin densitites in triplet benzophenone

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Abstract
The lowest photoexcited triplet state of benzophenone in single crystals of 4,4′‐dibromodiphenyl ether has been studied by optically detected ENDOR. The hyperfine coupling tensors for eight protons and carbonyl–13C have been determined by analyzing the angular dependence of the ENDOR spectra. A point–dipole model is presented to account for the anisotropic hyperfine tensor elements based solely on spin densitites and molecular geometry. A set of spin densities and a ring–twist angle have been found which, together, best reproduce the observed dipole interaction tensors as calculated from our model. Data from zero‐field ODMR experiments on 17O–benzophenone performed by S. Yamauchi and D. W. Pratt at the University of Pittsburgh enabled us to remove the correlation between n and π spin densities on oxygen. A final fit of all data shows the n electron to be localized on oxygen and the π electron to be delocalized onto the rings.