From intermolecular interactions to incipient chemical bond

摘要

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 C-state species, O-2 and NH, display typical non-covalent interactions, similar to closed-shell systems. Complexes of Pi-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(X(2)Pi) complex displays an incipient pi-bond on its A " surface, while a regular van der Waals interaction is observed on the A' surface. Interaction of a P-state chlorine atom with RG gives rise to two potential curves: Sigma and Pi. The Sigma state features an incipient sigma bond whereas the Pi-state surface reveals a van der Waals interaction. The excited state complex He + Cl-2(B(3)Pi(u)) illustrates a different situation, with both the A' and A " states fairly close to each other, with only slight indication of the incipient bond. [References: 42]