Semi-empirical calculations of the zero-field-splitting parameters of the lowest triplet states of aromatic ketones

Semi-empirical calculations of zero-field-splitting parameters have been performed for the lowest triplet states of aromatic ketones, the mixing between the nearly degenerate n, π* and π, π* triplet states through the vibronic and spin-orbit interactions being considered. The results show that the mixing through the spin-orbit interaction is important to explain the absolute values and signs of the zero-field-splitting parameters observed for acetophenone, p-chlorobenzaldehyde, and benzophenone. The observed and calculated D values are -0·1943 cm-1 and -0·180 cm-1 for the lowest triplet state of p-chlorobenzalhyde in p-dibromobenzene.