meso－四（4－磺苯基）卟啉对铕（Ⅲ）与羧酸络合物电还原的催化作用

Electro-catalytic Effect of meso-Tetra(4-sulfophenyl)·porphyrin on Voltammetric Behavior of Some Eu(Ⅲ)Carboxylic Acid Complexes in Aqueous Solution

水溶液中Ｅｕ^（３＋）与ｍｅｓｏ－四（４－磺苯基）卟啉（ＴＰＰＳ）不易形成卟啉络合物，但在乙酸、酒石酸、丙二酸等共存时，在循环伏安图上可得一对Ｅｕ^（３＋）还原－氧化的可逆或准可逆峰，此峰与Ｅｕ^（３＋）在ＮａＣｌＯ＿４底液中的还原峰相比，峰电位正移，峰电流增高。从６种Ｅｕ^（３＋）－羧酸络合物与ＴＰＰＳ共存时的实验中证明这些络合物并没有和ＴＰＰＳ形成三元络合物，而是吸附在汞电极上的ＴＰＰＳ产生电催化作用。

It is difficult to synthesize the complexes of rare earth ions with meso-tetra(4-sulfophenyl)porphyrin(TPPS)in aqueous solution. Eu(Ⅲ)can form complexes with carboxylic acids, such as acetic,tartaric, malonic, gluconic, citric acids and EDTA with different stability constants,and exhibits irreversible or quasi-reversible redox peaks in cyclic voltammograms. TPPS, which adsorbed on Hg electrode,exerts catalytic effect on the redox behvior of Eu(Ⅲ)-acetic, tartaric, malonic acid complexes by changing the irreversible process to a reversible one, but the Eu(Ⅲ)-TPPS complex was not formed.The mechanism of such a catalytic effect has been discussed.