Quantum-Chemical and Molecular Dynamics Study of M+[TOTO]- (M = Li, Na, K) Ionic Liquids

Quantum-chemical calculations and classical molecular dynamics simulations with the Optimized Potentials for Liquid Simulations-All Atom (OPLS-AA) force field are presented for ionic liquids based on 2,5,8,11-tetraoxatridecan-13-oate anion (TOTO) and alkali cations (Li, Na, K). Complexation energies decrease with increasing cation radius from Li to K. Cation interactions with carboxylate oxygen atoms are preferred over complexation to ether oxygens. Cross-linking occurs in the structure of the liquid because of interactions of multiple metal ions with carboxylate oxygen atoms from multiple TOTO anions. Anticorrelated motion of ions of the same charge is an important factor decreasing conductivity of the liquid. Results of modeling agree with available experimental data for Na-TOTO.