TY - JOUR
T1 - Isolated BMI+ cations are more than isolated PF6 - anions in the room temperature 1-butyl-3-methylimidazolium hexafluorophosphate (BMI-PF6) ionic liquid
AU - Chen, Wei Ting
AU - Hsu, Wen Yi
AU - Lin, Mei Yi
AU - Tai, Chia Cheng
AU - Wang, Shao Pin
AU - Sun, I. Wen
PY - 2010
Y1 - 2010
N2 - 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 physicalmeaning: 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- methylimidazoliumhexafluorophosphate (BMI-PF6), (BMI-PF 6)nPF6- anions are found preferred to (BMI-PF6)nBMI+ 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-PF6/2,2,2-trifluoroethane (TFE) mixtures at two different compositions (XTFE = 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.
AB - 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 physicalmeaning: 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- methylimidazoliumhexafluorophosphate (BMI-PF6), (BMI-PF 6)nPF6- anions are found preferred to (BMI-PF6)nBMI+ 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-PF6/2,2,2-trifluoroethane (TFE) mixtures at two different compositions (XTFE = 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.
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U2 - 10.1002/jccs.201000191
DO - 10.1002/jccs.201000191
M3 - Article
AN - SCOPUS:79952074682
SN - 0009-4536
VL - 57
SP - 1293
EP - 1298
JO - Journal of the Chinese Chemical Society
JF - Journal of the Chinese Chemical Society
IS - 6
ER -