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Isolated BMI + Cations are More than Isolated PF 6 − Anions in the Room Temperature 1‐Butyl‐3‐Methylimidazolium Hexafluorophosphate (BMI‐PF 6 ) Ionic Liquid
Author(s) -
Chen WeiTing,
Hsu WenYi,
Lin MeiYi,
Tai ChiaCheng,
Wang ShaoPin,
Sun IWen
Publication year - 2010
Publication title -
journal of the chinese chemical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.329
H-Index - 45
eISSN - 2192-6549
pISSN - 0009-4536
DOI - 10.1002/jccs.201000191
Subject(s) - ionic liquid , chemistry , hexafluorophosphate , thermal diffusivity , cationic polymerization , ionic bonding , ion , ion association , analytical chemistry (journal) , inorganic chemistry , thermodynamics , organic chemistry , physics , catalysis
Abstract Assuming various ionic states in ionic liquids (ILs) are in equilibrium with exchange rates too high to be distinguished by NMR experiments and the overall response of measured diffusivity is viewed as the sum of weighted responses of diffusivity of all possible components, the ratio of cation diffusivity to anion diffusivity, D + / D − , in a specified IL affords the physical meaning: relative association degrees observed by anion‐containing components to cation‐containing components. These values decrease with increasing temperature showing the equilibrium between ionic states shifting to smaller components. In the neat 1‐butyl‐3‐methylimidazolium hexafluorophosphate (BMI‐PF 6 ), (BMI‐PF 6 ) n PF 6 − anions are found preferred to (BMI‐PF 6 ) n BMI + cations and this phenomenon is termed as hyper anion preference (HAP). The counterpart statement, “isolated BMI + Cations Are More than Isolated PF 6 − Anions in the Room Temperature in the BMI‐PF 6 Ionic Liquid” is employed as the research title. The HAP approach can be employed to explain the temperature‐dependent values of D + / D − obtained for BMI‐PF 6 /2,2,2‐trifluoroethane (TFE) mixtures at two different compositions (χ TFE = 0.65 and 0.80). More significantly, this argument can rationalize numerous physical properties published for this IL: (1) higher sensitive of anionic diffusivity towards temperatures than cationic diffusivity, (2) temperature‐dependent cationic transference number, (3) low anionic donicity and high ionicity and (4) high viscosity.