title: Cation-pi-anion interaction in alkali ion-benzene-halogen ion clusters.
abstract: The present investigation on some ternary M(+)-benzene-X(-) aggregates follows previous studies concerning the binary, M(+)-benzene (M = Li, Na, K, Rb, Cs) and X(-)-benzene (X = F, Cl, Br, I), systems. A semimepirical model describing the intermolecular potential energy, formulated as a combination of few leading effective components, is here extended and applied to investigate more complex systems. The balancing of size repulsion with induction and dispersion attraction is described as a combination of ion-bond interactions and an electrostatic component, rationalized on the basis of the benzene quadrupole moment, is also included. For M(+)-benzene-X(-) aggregates, the simultaneous presence of a cation and an anion close to the pi system originates a strong Coulombic attraction and nonadditivity effects of the induction energy, which are carefully considered and explicitly included to obtain a proper analytical functional representation of the ternary compound. The proposed semiempirical methodology, providing the whole potential energy surface in a convenient analytical form, is useful to predict the main features of stable and unstable configurations, saddle points, and energy barriers, allowing for investigation of their influence on molecular dynamics simulations.
authors.affiliation: IQTCUB, Departament de Química Física, Universitat de Barcelona, Barcelona, Spain. m.alberti@ub.edu
authors.forename: Margarita
authors.initials: M
authors.lastname: Albertí
authors.forename: Antonio
authors.initials: A
authors.lastname: Aguilar
authors.forename: Fernando
authors.initials: F
authors.lastname: Pirani