title: A DFT study of the ground state multiplicities of linear vs angular polyheteroacenes.
abstract: Unrestricted density functional calculations in combination with the broken-symmetry approach and spin-projection methods have been employed to study a series of formally 4n pi antiaromatic linear and angular polyheteroacenes. Calculations show that the linear polyheteroacene molecules have either stable singlet zwitterionic 6-9 or singlet diradical 5 ground states because they sacrifice the aromaticity of the central arene to form two independent cyanines. The corresponding angular compounds 10-14 have robust triplet states, since they cannot create independent cyanines to escape their overall antiaromaticity. An analysis based on the SOMO-SOMO energy splittings, their spatial distributions, and the spin density populations for the triplet states is presented to clarify the factors that determine their ground state multiplicities.
authors.affiliation: Department of Chemistry, University of Cyprus, P.O. Box 20537, 1678 Nicosia, Cyprus.
authors.forename: Christos P
authors.initials: CP
authors.lastname: Constantinides
authors.forename: Panayiotis A
authors.initials: PA
authors.lastname: Koutentis
authors.forename: Jürgen
authors.initials: J
authors.lastname: Schatz