Current interest in the environmental presence and toxicological properties of cyclopenta [cd] pyrene has stimulated work on the synthesis and chemical and biological properties of related cyclopentene-fused polynuclear aromatic hydrocarbons (PAHs).'-~ Recently aceanthrylene (1) and acephenanthrylene (4), two non-bay-region PAHs, have been found to exhibit mutagenic a~ tivit 9~ and along with the interest in their excited-state properties! ...