Externally-fused cyclopenta moieties in non-alternant CP-PAHs act as peri-substituents

Abstract The Hammett constants σ m for the externally fused cyclopenta moiety in the CP-PAHs 1 (1,8-CP), 2 (1,9-CP), 3 (1,10-CP) and 4 (3,5-CP) have been determined. The σ m values for these structurally different CP-PAHs are nearly identical. This gives evidence that the cyclopenta moiety acts as a peri -substituent with σ m =0.4±0.07.