title: Low-temperature heat capacities of 1-alkyl-3-methylimidazolium bis(oxalato)borate ionic liquids and the influence of anion structural characteristics on thermodynamic properties.
abstract: Two chelated orthoborate ionic liquids (ILs), 1-butyl-3-methylimidazolium bis(oxalato)borate ([Bmim][BOB]) and 1-hexyl-3-methylimidazolium bis(oxalato)borate ([Hmim][BOB]), were prepared and characterized. Their thermodynamic properties were studied using adiabatic calorimetry and differential scanning calorimetry (DSC). The thermodynamic properties of the two ILs were evaluated and compared with each other, and then with those of other [Bmim] type ILs. The results clearly indicate that for a given cation (or anion) and at a certain temperature, the more atoms in the anion (or cation), the higher the heat capacity; the higher glass-transition temperatures of [BOB] type ILs than others are mainly caused by the higher symmetry of the orthoborate anion structure. It is suggested that a high content of strong electronegative atoms and C(n) or C(nv) (n = 1,2,3,…,∞) point group symmetry in the anion are favorable for the design and synthesis of room temperature ILs with a wide liquid range.
authors.affiliation: China Ionic Liquid Laboratory, Dalian Institute of Chemical Physics, Chinese Academy of Science, Zhongshan Road 457, Dalian, 116023, China.
authors.forename: Miao
authors.initials: M
authors.lastname: Yang
authors.forename: Jun-Ning
authors.initials: JN
authors.lastname: Zhao
authors.forename: Qing-Shan
authors.initials: QS
authors.lastname: Liu
authors.forename: Li-Xian
authors.initials: LX
authors.lastname: Sun
authors.forename: Pei-Fang
authors.initials: PF
authors.lastname: Yan
authors.forename: Zhi-Cheng
authors.initials: ZC
authors.lastname: Tan
authors.forename: Urs
authors.initials: U
authors.lastname: Welz-Biermann
mesh_terms: D000838:Anions / Q000737:chemistry; D001881:Borates / Q000138:chemical synthesis / Q000737:chemistry*; D002151:Calorimetry; D052578:Ionic Liquids / Q000138:chemical synthesis / Q000737:chemistry*; D015394:Molecular Structure; D013816:Thermodynamics
chemical_list: D000838:Anions; D001881:Borates; D052578:Ionic Liquids