Density functional theory study on lithium bis[1,2-benzenediolato(2-)-O,O′] borate and its derivatives:: electronic structures, energies, and molecular properties

Theoretical studies on electrolyte salts, lithium bis[1,2-benzenediolato(2-)-O,O'] borate (LBBB) and its derivatives, lithium bis[3-fluoro-1,2-benzenediolato(2-)-O,O']borate (1FLBBB), and lithium bis[tetrafluoro-1,2-benzenediolato(2-)-O,O'] borate(4FLBBB) are carried out using density functional theory (DFT) method and B3LYP theory level for the first time. Bidentate structures involving two oxygen atoms are preferred. The GIAO-DFT results for all molecules suggest that the corresponding RB3LYP/6-31++G(2df,2p) geometries can be deemed reasonably good representations of the geometries of relatively free molecules in solution. Based on these conformations, a linear correlation was observed between the highest occupied molecular orbital (HOMO) energies and the limiting oxidation potentials measured by linear sweep voltammetry, which supports experimental results that inorganic fluorine-containing anions are more resistant against oxidation than their organic counterparts. The correlations were also observed between ionic conductivity and binding energy, solubility and anion polarizability, thermal stability and the energy difference between E-LUMO and E-HOMO. Wave function analyses have been performed by natural bond orbital (NBO) method to further investigate the cation-anion interactions. (C) 2004 Elsevier Ltd. All rights reserved.