The potential surface for the least-motion dissociation of trans dimeric nitrosomethane. A limited non-conventional CI approach

Abstract

The potential surface for the least-motion dissociation of trans dimeric nitrosomethane into monomeric units has been investigated by application of a special configuration interaction procedure. The procedure consists in mixing configurational wavefunctions that have been determined by separate Hartee—Fock calculations. The configurations include in the present CI calculations are the five closed shell cofigurations that are required for an adequate description of the breaking of the NN bond and formation of two monomer molecules. The calculations indicate that the ground state configuration of the dimer be supplemented with an excited π → π* configuration if a satisfactory description of the molecule at equilibrium geometry is to be achieved. One would thus assume trans dimeric nitrosomethane to have a pronounced biradical character. Furthermore, the system has been found to be Hartee—Fock unstable at all NN distances investigated, a fact that can be related to the inadequacy of a one-configuration description of the molecule. The optimal NN and NO bond lengths obtained for the dimer are 1.3043 and 1.2982 A, respectively, in good agreement with experiment. The calculated dissociation energy is 31.9 kcal mole −1 which is about twice the experimental value.