Triplet-State Zero-Field-Splitting Correlations in Substituted Molecules

The triplet-state properties of a large number of unsaturated ring compounds have been investigated by optical and electron paramagnetic techniques. Correlative effects have been noted between optical zero-field-splitting (ZFS) shifts and chemical data. Redistribution of spin density due to substituents as evidenced by ZFS shifts appear to be directly related to measures of π charge redistribution using other techniques. For the naphthalene derivatives the dependence of ZFS shift on spin density at substitutional carbon site has been found also to correlate with triplet lifetimes.