Quentel François, Mirceski Valentin, L'Her Maurice
Laboratoire de Chimie Analytique, UMR-CNRS 6521, Université de Bretagne Occidentale, 6, avenue Victor Le Gorgeu, C. S. 93837, 29238 Brest Cedex, France.
Anal Chem. 2005 Apr 1;77(7):1940-9. doi: 10.1021/ac049117m.
The electrochemical oxidation of lutetium bis(tetra-tert-butylphthalocyaninato) (LBPC) and decamethylferrocene (DMFC), as well as the reduction of LBPC, lutetium bis(phthalocyaninato) (LPC), and lutetium (tetra-tert-butylphthalocyaninato hexadecachlorphthalocyaninato) (LBPCl), has been studied in a thin nitrobenzene (NB) film deposited on the surface of a graphite electrode (GE) by means of square-wave voltammetry (SWV). The organic film-modified electrode was immersed in an aqueous (W) electrolyte solution and used in a conventional three-electrode configuration. When the aqueous phase contains ClO4-, NO3-, or Cl- (ClO4-, or NO3- only, in the case of DMFC), both LBPC and DMFC are oxidized to stable monovalent cations in the organic phase. The electron transfer at the GE | NB interface is accompanied by a simultaneous anion transfer across the W | NB interface to preserve the electroneutrality of the organic phase. LBPC, LPC, and LBPCl are reduced to stable monovalent anions accompanied by expulsion of the anion of the electrolyte from the organic into the aqueous phase. In all cases, the overall electrochemical process comprises simultaneous electron and ion transfer across two separate interfaces. Under conditions of SWV, the overall electrochemical process is quasireversible, exhibiting a well-formed "quasireversible maximum" that is an intrinsic property of electrode reactions occurring in a limiting diffusion space. For all the redox compounds that have been studied, the kinetics of the overall electrochemical process is controlled by the rate of the ion transfer across the liquid | liquid interface. Based on the quasireversible maximum, a novel and simple methodology for measuring the rate of ion transfer across the liquid | liquid interface is proposed. A theoretical background explaining the role of the ion-transfer kinetics on the overall electrochemical process at the thin organic film modified electrode under conditions of SWV is presented. Comparing the positions of the theoretical and experimental quasireversible maximums, the kinetics of ClO4-, NO3-, and Cl- across the W | NB interface was estimated. The kinetics of the overall process at the thin organic film modified electrode, represented by the second-order standard rate constant, is 91 +/- 8, 90 +/- 4, and 133 +/- 10 cm(4) s(-1) mol(-1), for the transfer of ClO4-, NO3-, and Cl- respectively.
通过方波伏安法（SWV）研究了双（四叔丁基酞菁）镥（LBPC）和十甲基二茂铁（DMFC）的电化学氧化，以及LBPC、双（酞菁）镥（LPC）和镥（四叔丁基酞菁十六氯酞菁）（LBPCl）的还原。将有机膜修饰电极浸入水（W）电解质溶液中，并用于传统的三电极配置。当水相中含有ClO4-、NO3-或Cl-（对于DMFC，仅含ClO4-或NO3-）时，LBPC和DMFC在有机相中均被氧化为稳定的单价阳离子。在石墨电极（GE）|硝基苯（NB）界面处的电子转移伴随着阴离子同时穿过水|硝基苯界面，以保持有机相的电中性。LBPC、LPC和LBPCl被还原为稳定的单价阴离子，同时电解质阴离子从有机相排入水相。在所有情况下，整个电化学过程包括电子和离子同时穿过两个独立的界面。在SWV条件下，整个电化学过程是准可逆的，表现出一个形成良好的“准可逆最大值”，这是在极限扩散空间中发生的电极反应的固有特性。对于所有已研究的氧化还原化合物，整个电化学过程的动力学由离子穿过液|液界面的速率控制。基于准可逆最大值，提出了一种新颖且简单的测量离子穿过液|液界面速率的方法。给出了一个理论背景，解释了在SWV条件下离子转移动力学对薄有机膜修饰电极上整个电化学过程的作用。通过比较理论和实验准可逆最大值的位置，估计了ClO4-、NO3-和Cl-穿过水|硝基苯界面的动力学。对于ClO4-、NO3-和Cl-的转移，以二阶标准速率常数表示的薄有机膜修饰电极上整个过程的动力学分别为91±8、90±4和133±10 cm4 s-1 mol-1。
