学术文献库

Spiroborate anions based inorganic electrolytes and ionic liquids (ILs) have fascinating electrochemical and tribological properties, and have received widespread attention in industrial applications. Molecular chiralities of spiroborate anions have a significant effect on microstructures and macroscopic functionalities of these ionic materials in applications, and thus deserve a fundamental understanding. In current work, we performed quantum chemistry calculations to address binding strength and coordination structures of chiral bis(mandelato)borate ([BMB]) anions with representative alkali metal ions, as well as electronic properties of alkali metal ion-[BMB] ion pair complexes. The optimized [BMB] conformers are categorized into V-shaped, bent, and twisted structures with varied electrostatic potential contours, conformational energies, and distinct alkali metal ion-[BMB] binding structures. Alkali metal ions have additional associations with phenyl groups in V-shaped [BMB] conformers owing to preferential cation-$π$ interactions. Furthermore, effects of molecular chiralities of [BMB] anions on thermodynamics and microstructural properties of tetraalkylphosphonium [BMB] ILs were studied by performing extensive atomistic interactions. Oxygen atoms in [BMB] anions have competitive hydrogen bonding interactions with hydrogen atoms in cations depending on molecular chiralities and steric hindrance effects of [BMB] anions. However, molecular chiralities of [BMB] anions have negligible effect on liquid densities of tetraalkylphosphonium [BMB] ILs and spatial distributions of boron atoms in anions around phosphorous atoms in cations. Enlarging tetraalkylphosphonium cation sizes leads to enhanced cation-anion hydrogen bonding and Coulombic interactions due to enhanced segregation of polar groups in apolar networks in heterogeneous IL matrices.