Facilitated transfer of alkali-metal cations by dibenzo-18-crown-6 across the electrochemically polarized interface between an aqueous solution and a hydrophobic room-temperature ionic liquid
Facilitated transfer of alkali-metal cations by dibenzo-18-crown-6 across the electrochemically polarized interface between an aqueous solution and a hydrophobic room-temperature ionic liquid
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DOI：
10.1021/ac060797y
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发表时间：
2006-08-15
影响因子：
7.4
通讯作者：
Kakiuchi, Takashi
中科院分区：
文献类型：
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作者：
Nishi, Naoya;Murakami, Hiroshi;Kakiuchi, Takashi
用循环伏安法研究了二苯并-18-冠-6(DB18C6)促进碱金属阳离子(Li+、Na+、K+、Rb+、Cs+)在水溶液(W)和疏水离子液体N-十八烷基异喹啉tetrakis[3，5-bis(trifluoromethyl)phenyl]borate([C(18)IQ][TFPB])之间的电化学极化转移。在循环伏安(CVs)中，DB18C6促进阳离子从W转移到[C(18)IQ][TFPB]的电流可以在[C(18)IQ][TFPB]JW界面的极化电位窗口内测量到。对于Li+、Na+、K+和Rb+，[C(18)IQ][TFPB]中的络合物的化学计量比为1：1，而对于Cs+的转移，可能形成1：1和1：2的络合物。[C(18)IQ][TFPB]，K-f(R)中Li+、Na+、K+和Rb+的1：1络合物的生成常数分别为logK-f(R)=5.0、7.0、8.2和7.3。K+的K-f(R)值比Na+的大1个数量级。与在分子溶剂中相比，在[C(18)IQ][TFPB]中，DB18C6对K+的选择性高于对Na+的选择性，这表明RTIL为DB18C6与离子的络合提供了独特的溶剂化环境。
The facilitated transfer of alkali metal cations (Li+, Na+, K+, Rb+, Cs+) by dibenzo-18-crown-6 (DB18C6) across the electrochemically polarizable interface between an aqueous solution (W) and a hydrophobic ionic liquid, N-octadecylisoquinolinium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate ([C(18)Iq][TFPB]), has been studied using cyclic voltammetry at the interface formed at the tip of a micropipet. In cyclic voltammograms (CVs), the current due to the facilitated transfer of the cations by DB18C6 from W to [C(18)Iq][TFPB] can be measured within the polarized potential window of the [C(18)Iq][TFPB]jW interface. The stoichiometry of the complexes in [C(18)Iq][TFPB] for Li+, Na+, K+, and Rb+ are found to be 1: 1 while for the Cs+ transfer both 1: 1 and 1: 2 complexes are likely to be formed. The formation constants of the 1: 1 complexes for Li+, Na+, K+, and Rb+ in [C(18)Iq][TFPB], K-f(R), evaluated from CVs are log K-f(R) = 5.0, 7.0, 8.2, and 7.3, respectively. The K-f(R) value for K+ is 1 order of magnitude greater than that for Na+. This higher selectivity of DB18C6 to K+ over Na+ in [C(18)Iq][ TFPB] compared with that in molecular solvents suggests that the RTIL provides a unique solvation environment for the complexations of DB18C6 with the ions.