Solvation of Li+ by acetone, THF, and diethyl ether in the gas phase and the ion-molecule association mechanism

Fourier transform ion cyclotron resonance spectrometry has been employed to study the solvation of the Li+ ion with acetone, tetrahydrofuran (THF), and diethyl ether (DEE) in the gas phase. LiILi+ triple ions are produced in the ICR cell by the laser desorption ionization of a lithium iodine/dibenzo-18-crown-6-ether matrix pasted on a Teflon substrate. All O donors abstract Li+ from the triple ion and form solvated complexes with a maximum solvation number of three at room temperature, around 10(-6) Torr. All third solvent binding energies are determined from van't Hoff plots. Structures and energetics of the Li+.(S)(n) complexes, where n = 1-4 for acetone and THF and n = 1-3 for DEE. have been calculated at the Hartree-Fock level with a 6-311+G(d,p) basis set. Solvation enthalpies and free energies are calculated, and solvent binding enthalpies are compared with experiments. The kinetics of solvent exchange and the association reactions of Li+.(acetone-h(6))(acetone-d(6)) with a 1:1 acetone-h(6)/acetone-d(6) mixture have been measured as a function of pressure. The lifetime of the collision complexes are derived and compared with phase space theory calculations. The isotope effect on the radiative cooling rate is discussed.X1130sciescopu