Collect. Czech. Chem. Commun. 1998, 63, 1473-1484

From Intermolecular Interactions to Incipient Chemical Bond

Grzegorz Chałasińskia, Jacek Klosa, Slawomir M. Cybulskib and Małgorzata M. Szczęśniakc

a Department of Chemistry, University of Warsaw, Pasteura 1, 02-093 Warszawa, Poland
b Department of Chemistry, Miami University, Oxford, Ohio 45056, U.S.A.
c Department of Chemistry, Oakland University, Rochester, MI 48309, U.S.A.


The complexes of a rare gas atom (RG) and a number of open-shell molecules are discussed in the context of the bond character, structural and dynamical properties. The potential energy surfaces of a variety of complexes have been obtained using the combination of highly correlated supermolecular approach and the symmetry-adapted perturbation theory. Complexes of Σ-state species, O2 and NH, display typical non-covalent interactions, similar to closed-shell systems. Complexes of Π-state species are represented by pairs of adiabatic potentials A' and A'' due to removal of degeneracy through the interaction with the RG moiety. The two states may have distinctly different character. The He-CH(X2Π) complex displays an incipient π-bond on its A'' surface, while a regular van der Waals interaction is observed on the A' surface. Interaction of a Π-state chlorine atom with RG gives rise to two potential curves: Σ and Π. The Σ state features an incipient σ bond whereas the Π-state surface reveals a van der Waals interaction. The excited state complex He + Cl2(B3Πu) illustrates a different situation, with both the A' and A'' states fairly close to each other, with only slight indication of the incipient bond.

Keywords: Intermolecular interactions; Van der Waals complexes; Molecular clusters; Rare gases complexes; Ab initio calculations.