Evaluation of AM1‐calculated radical cation ion‐neutral complexes

Abstract

AbstractAM1 semiempirical molecular orbital calculations are reported for 20 ion‐neutral complexes, including hydrogen‐bonded complexes, presumably involved in the gas‐phase unimolecular decomposition of simple organic radical cations. The systems investigated are [C2H4O2]˙+, [C2H5NO]˙+, [C2H6O]˙+, [C2H6O2]˙+, [C3H6O]˙+, [C3H6O2]˙+, [C3H8O]˙+, and [C3H8O2]˙+. The AM1 results are compared with ab initio molecular orbital calculations at different levels of theory up to MP3/6‐31G(d, p)//SCF/6‐31G(d) + ZPVE and the available experimental data. AM1 fails to predict some local minima and the equilibrium geometries calculated for several complexes are found to be qualitatively different from those predicted by the ab initio calculations. However, reasonable agreement is generally found for the stabilization energies of the complexes toward dissociation into their loosely bound components. © John Wiley & Sons, Inc.