title: Effect of benzo-annelation on local aromaticity in heterocyclic conjugated compounds.
abstract: The effect of benzo-annelation on the local aromaticity of the central ring of acridine (1), 9H-carbazole (2), dibenzofuran (3), and dibenzothiophene (4) was analyzed by means of the energy effects (ef), pairwise energy effects (pef), multicenter delocalization index (MCI), electron density at ring critical points (ρ(r(C))), harmonic oscillator model of aromaticity (HOMA), and nucleus independent chemical shifts (NICS). According to energetic, electron delocalization, and geometrical indices, angular benzo-annelation increases, whereas linear benzo-annelation decreases, the extent of the local aromaticity of the central ring containing heteroatoms. The local aromaticity of the central heterocyclic ring in the examined molecules can significantly vary by applying different modes of benzo-annelation. The NICS values do not always support the results obtained by the other aromaticity indices and, in some cases, lead to completely opposite conclusions.
authors.affiliation: Faculty of Science, University of Kragujevac , 12 Radoja Domanovića, 34000 Kragujevac, Serbia.
authors.forename: Slavko
authors.initials: S
authors.lastname: Radenković
authors.forename: Jelena
authors.initials: J
authors.lastname: Kojić
authors.forename: Jelena
authors.initials: J
authors.lastname: Petronijević
authors.forename: Marija
authors.initials: M
authors.lastname: Antić