Light-dependent isomeric effects of polycyclic aromatic hydrocarbons on the predication of DNA cleavage factor efficiency

PAHs, short for polycyclic aromatic hydrocarbons, are a ubiquitous group of chemically related, environmentally persistent organic compounds having diverse structures and varied toxicity. They have been shown to cause mutagenic and carcinogenic effects on organisms and are quite immunosuppressive. Time-dependent density functional theory (TD-DFT) offers a practical means of understanding the behavior of excitation energies for PAHs. Here, we examined the performance of the long-range corrected Coulomb-attenuating functional (CAM-B3LYP) in relation to four different basis sets, determining which basis set compliments the functional better in identifying the most reactive atomic site on six isomeric PAH compounds. Condensed Fukui function indices were used to compare the performance of applied basis sets in identifying the most reactive atomic site on six isomeric PAHs compounds, assessing which basis set would be more appropriate in determining the site where free-radical formation would occur after light irradiation. Dunning's correlation consistent triple-zeta (cc-pVTZ) basis set was determined to have the best PAH characterization performance, concluding the need for application of a higher-level basis set with the long-range corrected Coulomb-attenuating functional. Although each compound was a structural isomer of the other, the reactive atomic sites varied for each molecule with the use of an applied basis set. It was concluded that structural shape has some influence on the calculation of PAH characteristics. Lastly, in order to predict DNA single-stranded cleavage factor for the compounds proposed here, we have used the quantitative structure-activity relationship (QSAR). The cleavage factor values for the set of aromatic molecules with similar structures have been collected from the literature for a total number of 22 compounds.