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Abstract

The electrochemical oxidation of solutions of silver(I) nitrate and silver(I) perchlorate in the presence of various polypyridyl ligands in acetonitrile was studied using the techniques of polarography and controlled potential coulometry. Tetra-n-butylammonium perchlorate was used as the supporting electrolyte. In the absence of ligand, silver(I) nitrate gave a single oxidation wave which was found to correspond to the one-electron oxidation of the nitrate ion. In the presence of ligand, two oxidation waves were observed, the first of which corresponded to the one-electron oxidation of silver(I) complex; this was confirmed by coulometric determinations. The second wave was thought to be associated with the catalytic oxidation of the ligand molecule.

A detailed polarographic study of the silver(I) nitrate/2,2'-bipyridyl system showed that the limiting current of the Ag(I)/Ag(II) wave was proportional to the concentration of the intermediate complex, Ag(bipy)+; this was interpreted in terms of a kinetically controlled wave involving Ag(bipy)+ as the precursor of the electroactive species.

Preparative scale electrolyses at controlled potentials corresponding to the first anodic wave of the silver(I)/polypyridyl systems were carried out, and several silver(II) complexes were isolated. In the case of silver(I) nitrate in the presence of 2,2'-bipyridyl and 4,4'-dimethyl-2,2'-bipyridyl, silver(II) complexes of the type [AgL]NO3·ClO4 were obtained. These ligands gave complexes of the type [AgL](ClO4)2 when silver(I) perchlorate was used as the source of Ag(I). Silver(I)/2,2',2"-terpyridyl systems yielded a silver(II) complex of the type [AgL2](ClO4)2 irrespective of which silver(I) salt was used. Although coulometric studies established a one-electron change for the first wave of the silver(I)/5,5'-dibutyl-2,2'-bipyridyl system, the resulting silver(II) was not isolated.

A preliminary study of electro-oxidation of Cu(II)/2,2'-bipyridyl and Ni(II)/2,2'-bipyridyl systems indicated that, in the case of Ni(II), oxidation to a higher oxidation state occurred. However, attempts to isolate the complex were unsuccessful.

Publication Type:	Thesis (Doctoral)
Subjects:	Q Science > QD Chemistry T Technology > TP Chemical technology
Departments:	School of Science & Technology > School of Science & Technology Doctoral Theses Doctoral Theses

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