Voltammetric and impedance study of the binding of ferrocene derivatives to a sulfonated calix[6]arene host in aqueous solutions
Voltammetric and impedance study of the binding of ferrocene derivatives to a sulfonated calix[6]arene host in aqueous solutions
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DOI：
10.1016/s0022-0728(02)00739-8
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发表时间：
2002-04-19
影响因子：
4.5
通讯作者：
Tanabe, J
中科院分区：
文献类型：
--
作者：
Komura, T;Yamaguchi, T;Tanabe, J
本文研究了水介质中主客体络合作用对二茂铁氧化还原反应热力学和动力学参数的影响。的二茂铁/二茂铁对检查转移到不太积极的值与杯芳烃浓度的正式电位。因为形成了1：1的包合物。结合常数的大小顺序为阳离子二茂铁>不带电二茂铁>阴离子二茂铁。具有较高正电荷的氧化形式比相应的还原形式更强烈地结合到宿主上。结果与β-环糊精的观察结果相反。磺化杯[6]芳烃形成的包合物通过带负电荷的主体和阳离子客体之间的静电相互作用而大大稳定。快速扫描伏安行为表明，在低于2 V s（-1）的扫描速率范围内，内含物-喷射过程实际上达到平衡。电极反应的法拉第阻抗的Randles图实际上包括两条几乎平行的直线，在10（2）-10（3）Hz的频率范围内具有小的间隔，表明化学反应阻抗可忽略不计。随着主体浓度的增加，（二茂铁基-甲基）三甲基铵阳离子的平均扩散系数从6.0 x 10（6）cm（2）s（1）的自由离子成反比降低到（2.1 +/- 0.2）x 10（-6）cm（2）s（-1）的相应包合物。阻抗分析的结果表明，所包含的客体不与电极直接交换电子。(C)出版社：Elsevier Science B. V.
This report describes the effect of host-guest complexation on the thermodynamic and kinetic parameters of ferrocene redox reactions in aqueous media. The formal potentials of the ferrocene/ferrocenium couples examined shifted to less positive values with increasing calixarene concentration. because of the formation of a 1:1 inclusion compound. The order of binding constants was cationic ferrocene much greater than non-charged ferrocene > anionic ferrocene. The oxidized form with a higher positive charge was bound more strongly to the host than was the corresponding reduced form. The result was contrary to that observed for beta-cyclodextrin. The inclusion compounds formed by sulfonated calix[6]arene were greatly stabilized by an electrostatic interaction between the negatively charged host and cationic guest. Fast-scan voltammetric behavior suggested that inclusion-ejection processes practically attain equilibrium in the scan-rate range below 2 V s(-1), Randles plots for the Faradaic impedance of the electrode reaction virtually comprised two nearly parallel straight lines with a small separation over the frequency range of 10(2) - 10 (3).Hz, indicating negligible chemical reaction impedance. As the host concentration increased, the mean diffusion coefficient of the (ferrocenyl-methyl) trimethylammonium cation decreased inversely proportionally from 6.0 x 10 (6) cm(2) s (1) of the free ion to (2.1 +/- 0.2) x 10(-6) cm(2) s(-1) of the corresponding inclusion complex. The result of the impedance analysis suggests that the included guest exchanges no electrons directly with the electrode. (C) 2002 Published by Elsevier Science B.V.