Absolute Binding Energies of Alkali-Metal Cation Complexes with Benzene Determined by Threshold Collision-Induced Dissociation Experiments and ab Initio Theory

Abstract

The sequential bond dissociation energies (BDEs) of the mono- and bis-benzene complexes with alkali metal cations (Li+, Na+, K+, Rb+, and Cs+) are determined experimentally by collision-induced dissociation (CID) with Xe in a guided ion beam mass spectrometer and theoretically by ab initio calculations. The kinetic energy dependence of the CID cross sections are analyzed to yield 0 and 298 K bond energies for (C6H6)x-1M+−C6H6 (x = 1−2) after accounting for the effects of the internal energies of the reactant ions, the multiple collisions of the ions with xenon, and the dissociation lifetimes of the ionic complexes. Ab initio binding energies are calculated at the MP2(full)/6-311+G(2d,2p)//MP2(full)/6-31G* level and corrected for zero-point energies (ZPE) and basis set superposition errors (BSSE). The theoretical BDEs are in reasonably good agreement with the experimentally determined 0 K bond energies when full electron correlation is included (for Li+, Na+, and K+) but differ appreciably when effective c...