Relationship between resonance energy and carcinogenicity of azaarenes.

Resonance energy per pi-electron (REPE) of azaarenes were calculated by Aihara's theory of resonance energy (TRE). Consequently, it was shown that the REPE values for the cationic species not having the carbon, or nitrogen atom with the highest approximate superdelocalizability (Sr'(E)) in the parent skeleton were more unstable than those of their parent skeleton. Some correlations seem to exist between the REPE values for the cationic species not having the atom with the highest value of (Sr'(E)) in parent skeleton and carcinogenic activity. Other types of correlations can be assumed in the case of carbazoles 7H-benzo[g]pyrido[2,3-a]carbazole (14), 13H-dibenzo[a]pyrido[3,2-i]carbazole (17), and 7H-benzo[c]pyrido[2,3-g]carbazole (20) although there are some exceptions, i.e., 7H-benzo[g]pyrido[3,2-a]carbazole (15) and 7H-dibenzo[c,g]-carbazole (18). The bond-order affected carcinogenicity induction in some ways as well.