An Ab initio study of the relationship between nitroarene mutagenicity and electron affinity

Electron affinities, approximated by lowest unoccupied molecular orbital (LUMO) energies, were determined for an extensive group of nitrated polycyclic aromatic hydrocarbons by ab initio methods at the STO-3G level. Significant correlations were demonstrated between nitroarene LUMO energy and the corresponding mutagenic activity in Salmonella typhimurium strains TA98, TA100, TA1537, and TA1538. An analogous correlation using Hückel calculations was substantially poorer. A correlation between nitro group rotation and LUMO energy was related to pi-conjugation about the C--N bond. Analysis of aryl substituent effects on nitrenium ion stability implicated additional nitro substitution in certain systems to be destabilizing. The results suggest a means for predicting nitroarene mutagenic activity and for assessing the role of metabolic intermediates.