Prediction of mutagenic activity of nitronaphthalene isomers by infrared and Raman spectroscopy

IR and Raman spectra of 1- and 2-nitronaphthalene isomers (1-NN and 2-NN) have been investigated to obtain more insight into the effect of the structure on mutagenic properties. To this purpose we have performed density functional theory calculations using B3LYP functional with cc-pVDZ basis set. The results have shown that IR and Raman spectra of nitronaphthalene isomers are somewhat similar to each other. A notable exception regards the symmetrical NO bonds stretching +CN bond stretching vibration (nusNO2+nuCN), which appears as very intense peak near 1350 cm(-1) in IR and Raman spectra of both isomers. Present calculations predict that for 2-NN isomer IR and Raman absorptions of this vibration are more intense by ca. 50 and 60%, respectively, than those of 1-NN isomer. The noticeably higher IR and Raman intensity values of the nusNO2+nuCN mode for 2-NN originate, respectively, from large dipole moment and polarizability changes with respect to the normal mode, suggesting that intermolecular interactions are especially favoured along this coordinate. These results are consistent with higher mutagenic activities of 2-NN in comparison to 1-NN isomer, supporting the binding to enzyme mechanism as a determining step in mutagenic pathways for this series of nitroaromatic compounds.