title: First-principles molecular dynamics evaluation of thermal effects on the NMR (1)J(Li,C) spin-spin coupling.
abstract: Car-Parrinello (CP) molecular dynamics were applied to sample conformations of various models of organolithium aggregates which are chosen to estimate (1)J(Li,C) NMR coupling constants. The results show that the deviations from the values computed using static (optimized) geometries are small provided no large-amplitude motions occur within the timescale of the simulations. In the case of the vinyllithium dimer, for which rotation of the vinyl chain is observed, this approach allows analysis of the various contributions to the experimentally measured constants. For the trisolvated methyllithium monomer, partial decoordination of solvating dimethyl ether is observed and results in a significant shift of (1)J(Li,C). All these results highlight that a varied physicochemical machinery is hidden behind general empirical formulas, such as the Bauer-Winchester-Schleyer rule used experimentally.
authors.affiliation: Laboratoire de Chimie Théorique, UMR 7616 CNRS, Université P. and M. Curie, Case Courrier 137, 4, place Jussieu, 75252 Paris Cedex 05, France.
authors.forename: Aurélien
authors.initials: A
authors.lastname: de la Lande
authors.forename: Catherine
authors.initials: C
authors.lastname: Fressigné
authors.forename: Hélène
authors.initials: H
authors.lastname: Gérard
authors.forename: Jacques
authors.initials: J
authors.lastname: Maddaluno
authors.forename: Olivier
authors.initials: O
authors.lastname: Parisel