Quantum chemistry study of Li+-1,2-dimethoxypropane complexes

Quantum chemistry studies of the lowest energy conformers of 1,2-dimethoxypropane (DMP) complexes with Li+ ions have been carried out. Results of these calculations are compared with those of our recent study of Li+-1,2-dimethoxyethane (DME) complexes. Because of a chiral center, conformation space is more complex for DMP than for the structurally similar but achiral DME. Qualitatively similar behavior to that seen previously in studies of DME is found, however, including the presence of low-energy conformers containing consecutive gauche dihedrals of opposite sense and stronger interactions of the Li+ ion with conformers containing O-C-C-O gauche conformations, The former is a result of stabilization of conformers by attractive 1,5 CH3-O electrostatic interactions, while the latter reflects the ability of the ion to interact with both ether oxygen atoms. The calculated Li+-DMP complex energies and geometries reveal that favorable interactions of the or methyl group with the ion result in a Li+-t (g) over bar t complex energy comparable that of the Li+-tgt complex. Comparison of calculated Raman spectra with experimental measurements on DMP/LiClOs4 solutions indicates an increasingly high population of the t (g) over bar t conformer with increasing salt content.