Theoretical calculation of gas-phase ionization potentials for mono- and polysubstituted benzenes

This Letter provides an accurate and efficient method to obtain gas-phase ionization potentials for monosubstituted benzene molecules, using density functional theory with the B3LYP functional and geometry/frequencies obtained by the AM1 method. The results show an excellent correlation between calculated and experimental IPs for 20 different monosubstituted benzene rings. The study is extended to include polymethylated benzenes, up to hexamethylbenzene, whose IPs are also shown to be in good agreement with experimental data, making this a promising approach for large, polysubstituted benzene systems.