Potential coupling of intramolecular to intermolecular modes: an ab initiostudy of the amino inversion and van der Waals motions in the aniline-argon complex

In this paper, we present a description of the vibrating aniline-argon (An- Ar) van der Waals complex in its electronic ground state by using second or der Moller-Plesset (MP2) theory to elucidate the key factors which govern t he configuration of this complex. The interaction between the intramolecula r mode associated to the inversion motion of the amino group and the van de r Waals bending mode involving the motion of the Ar atom in the direction t oward the nitrogen atom, has been modeled. The ab initio results indicate n ot only that there is a significant coupling between the two motions, in ag reement with experimental findings on vibrational predissociation, but also that the interaction between the Ar atom and the nitrogen lone pair govern s the complex topology of this four-dimensional potential energy surface. ( C) 2001 Elsevier Science B.V, All rights reserved.