Relationship between resonance energy and carcinogenic activity of benz[c]acridines

In order to investigate the correlation between the carcinogenic activity of benz[c]acridines and the electron density, the Huckel orbital method was used. Resonance energies, circuit resonance energies and bond currents of benz[c]acridines were calculated by Aihara's TRE theory. It was shown that these compounds had very stable aromatic characters with positive resonance energies and that the resonance energies per pi-electron values for the compounds with lack of the double bond corresponding to the K-region from the parent skeleton were more stable than those of their parent compounds. 7-Methyl-benz[c]acridine derivatives with the methyl groups at 7-, 7, 9-, 7, 10-, 7, 11-, 7, 9, 10-, or 7, 9, 11-positions except 5, 7-dimethylbenz[c]acridine had potent carcinogenic activity and significantly lower resonance energy per pi-electron.