Abstract
The zero‐field splitting parameters D, E, and D* are calculated theoretically for the lowest triplet states of five polyphenyl benzenes. The agreement between theory and experiment is good. The calculated values for D* are uniformly too high by about 5%‐10%. The calculations indicate that the ring‐ring bond in biphenyl has double‐bond character in its lowest triplet state and, therefore, the molecule is planar in its phosphorescent state.