title: Analysis of aromaticity in planar metal systems using the linear response kernel.
abstract: The linear response kernel is used to gain insight into the aromatic behavior of the less classical metal aromatic E4(2-) and CE4(2-) (E = Al, Ga) clusters. The effect of the systematic replacement of the aluminum atoms in Al4(2-) and CAl4(2-) by germanium atoms is studied using, Al3Ge-, Al2Ge2, AlGe3+, Ge4(2+), CAl3Ge-, CAl2Ge2, CAlGe3+, and CGe4(2+). The results are compared with the values of the delocalization index (δ(1,3)) and nucleus independent chemical shifts (NICS(zz)). Unintegrated plots of the linear response, computed for the first time on molecules, are used to analyze the delocalization in these clusters. All aromaticity indices studied, the linear response, δ(1,3), and NICS(zz), predict that the systems with a central carbon are less aromatic than the systems without a central carbon atom. Also, the linear response is more pronounced in the σ-electron density than in the π-density, pointing out that the systems are mainly σ-aromatic.
authors.affiliation: General Chemistry, Free University of Brussels, Pleinlaan 2, B-1050 Brussels, Belgium. sfias@vub.ac.be
authors.forename: Stijn
authors.initials: S
authors.lastname: Fias
authors.forename: Zino
authors.initials: Z
authors.lastname: Boisdenghien
authors.forename: Thijs
authors.initials: T
authors.lastname: Stuyver
authors.forename: Martha
authors.initials: M
authors.lastname: Audiffred
authors.forename: Gabriel
authors.initials: G
authors.lastname: Merino
authors.forename: Paul
authors.initials: P
authors.lastname: Geerlings
authors.forename: Frank
authors.initials: F
authors.lastname: de Proft