title: Molecular mechanics (MM3) calculations on lithium amide compounds.
abstract: The MM3 force field has been extended to deal with the lithium amide molecules that are widely used as efficient catalysts for stereoselective asymmetric synthesis. The MM3 force field parameters have been determined on the basis of the ab initio MP2/6-31G* and/or DFT (B3LYP/6-31G*, B3-PW91/6-31G*) geometry optimization calculations. To evaluate the electronic interactions specific to the lithium amides derived from the diamine molecules properly, the Lewis bonding potential term for the interaction between the lithium atom and the nonbonded adjacent electronegative atom such as nitrogen was introduced into the MM3 force field. The bond dipoles were evaluated correctly from the electronic charges on the atoms calculated by fitting to the electrostatic potential at points selected. The MM3 results on the molecular structures, conformational energies, and vibrational spectra show good agreement with those from the quantum mechanical calculations.
authors.affiliation: Department of Applied Chemistry, Yokohama National University, 79-5 Tokoiwadai, Hodogaya-ku, Yokohama 240-8501, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Yoshida
authors.forename: Kazuhisa
authors.initials: K
authors.lastname: Sakakibara
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Asami
authors.forename: Kuo-Hsiang
authors.initials: KH
authors.lastname: Chen
authors.forename: Jenn-Huei
authors.initials: JH
authors.lastname: Lii
authors.forename: Norman L
authors.initials: NL
authors.lastname: Allinger