Molecular dynamics of BMI-PF6 in various solutions by 19F-NMR relaxation and 1H-NMR diffusion

• Main Authors: Kuo-Chih Cheng, 鄭國志
• Other Authors: Shiao-Ping Wang
• Format: Others
• Language: zh-TW
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/35212014595844852761

碩士 === 國立成功大學 === 化學系碩博士班 === 94 === 　　1-butyl-3-methylimidazolium hexafluorophosphate (BMI-PF6) is one of the most popular and investigated classes of room temperature ionic liquid. The nature of interaction between BMI-PF6 and solvents has been investigated by analyzing NMR diffusion coefficient of (1) BMI containing species and (2) aprotic organic solvents (AOS), including Acetontrile (AN), Propylene Carbonate (PC), N,N-dimethylformamide (DMF), Methyl Sulfoxide (DMSO). It has been found the self-diffusing ions are associated to different extents, depending on AOS-anion interactions in the order: PC > DMSO > DMF > AN. The strengths of ionicity, quantified in terms of “degree of dissociation,” which are evaluated by proposed “the method of ratio of diffusion coefficient.” The association capabilities, dissociation of bridged ion-pairs, are in the reverse order of the above-mentioned AOS-PF6 interaction trend. 　　The AN solvent, as predicted by its small dielectric constant, results in complete paired ( vanishing dissociation ) IL in the range of experimental temperature and concentration. DMF has similar magnitudes of e to that of AN, but can interact better with IL, revealed by a larger degree of dissociation of IL in DMF. PC has slightly larger value of dielectric constant than DMSO, but considerably stronger interaction with PF6 than DMSO. This can explain the much better dissociation of IL found experimentally in PC than in DMSO.