Cation−Ether Complexes in the Gas Phase: Bond Dissociation Energies and Equilibrium Structures of Li+(1,2-dimethoxyethane)x, x = 1 and 2, and Li+(12-crown-4)

Abstract

Bond dissociation energies, equilibrium structures, and harmonic vibrational frequencies are reported for Li+(DXE), where DXE = CH3O(CH2)2OCH3, Li+(DXE)2, and Li+(12-crown-4). The bond dissociation energies are determined experimentally by analysis of the thresholds for collision-induced dissociation of the cation−ether complexes by xenon (measured using guided ion beam mass spectrometry) and computationally by ab initio electronic structure calculations. For Li+(DXE)x, x = 1 and 2, the primary and lowest energy dissociation channel observed experimentally is endothermic loss of one dimethoxyethane molecule. For Li+(12-crown-4), the primary dissociation channel is endothermic loss of the intact crown ether, although ligand fragmentation is also observed. The cross section thresholds are interpreted to yield 0 and 298 K bond energies after accounting for the effects of multiple ion−molecule collisions, internal energy of the complexes, and unimolecular decay rates. The calculated and experimentally-derived...