AbstractThe photoexcited triplet states of the physically bound (intercalated) complexes of benzanthracene, pyrene, and free base porphin with DNA have been examined at 77 and 2 K. Measurements of triplet lifetimes, zero field splittings, and individual triplet sublevel intcrsystem crossing rates were obtained by optically detected zero field magnetic resonance (ODMR) for the benzan‐thracene‐DNA and free base porphin‐DNA complexes. The triplet lifetime was measured for the pyrene‐DNA complex. No ODMR was observable in the pyrene‐DNA system. Comparison of triplet state data with new and previous results for the benzo(a)pyrene‐DN A complex is discussed in an attempt to characterize the interactions experienced by polycyclic aromatic hydrocarbons and porphyrins within the DNA