吡啶存在下(TPP)Co的电化学氧化还原行为研究

Cyclic Voltammetric Investigation of the Axial Coordination Effects of Pyridine on the Redox Behaviours of (TPP)Co

本文考察了吡啶（Ｐｙ）对（ＴＰＰ）Ｃｏ在１，２－二氧乙烷中的电化学氧化还原行为的影响，观察到当存在一定量Ｐｙ时，Ｃｏ（Ⅲ）／Ｃｏ（Ⅱ）还原过程出现两个还原峰，分别在０．２５和－０．４０Ｖ（ｖｓ．ＳＣＥ）两处．由于吡啶在电极表面的吸附，在远小于形成二轴向Ｐｙ配合物的加入量时，Ｃｏ（Ⅲ）／Ｃｏ（Ⅱ）还原过程表现出了二个吡啶轴向配合物的伏安行为．证明在０．２５Ｖ与－０．４０Ｖ两个还原峰分别对应于一个和两个Ｐｙ分子配位的Ｃｏ（Ⅲ）／Ｃｏ（Ⅱ）还原峰．本工作还观察到了Ｃｏ（Ⅱ）／Ｃｏ（Ⅰ）还原受吡啶影响的伏安图变化过程，证实在－１．２Ｖ（ＳＣＥ）的还原峰是（ＴＰＰ）Ｃｏ（Ｐｙ）的直接电极还原．给出了Ｐｙ存在下（ＴＰＰ）Ｃｏ金属中心电化学氧化还原电位发生负移的机理．

The electrochemistry of (TPP)Co in presence of pyridine was investigated in dichloroethane solution by cyclic voltammetry. Upon the addition of pyridine to the solution, two reduction peaks of Co(Ⅲ)/Co(Ⅱ) at 0.25 and -0.40 V (SCE) were observed. It was infered that the peaks were belong to the reductions of the complex compounds with one and two axial pyridine, (TPP)Co(Ⅲ)(Py) and (TPP)Co(Ⅲ)(Py)2. Even though the mole ratio of added pyridine was less than 1 the reduction of Co(Ⅲ)/Co(Ⅱ) still mainly occured at -0.40 V, which evidently resulted from pyridine adsorption on the electrodes. Besides, it was observed that the reduction peak of Co(Ⅱ)/Co(Ⅰ) was shifted to -1.20 V (SCE) with large amount of added pyridine. The new reduction peak could be attributed to the direct reduction of the axially coordination complex (TPP)Co(Ⅱ)(Py). The mechanisms of the effect of pyridine on the electrochemical redox behaviours of (TPP)Co were given.