Abstract:
This thesis describes investigations into the nature of the complexes formed between the copper(II) ion and dimethylglyoxime in solution. Titrimetric methods were employed. The pH and/or the absorbance of the solutions being titrated were monitored. When a copper(II) solution is titrated with sodium dimethylglyoximate (Na2dmg), a grey-green precipitate is formed and a sharp increase in pH occurs at a point corresponding to a Cu : dmg stoichiometry of 1 : 1. In the photometric studies, a buffered solution of Na2dmg was titrated with Cu(II), while monitoring the absorbance at 430 nm. A plot of absorbance against volume of titrant shows two points of discontinuity, one corresponding to a Cu : dmg ratio of 1 : 2 and a second at a Cu : dmg ratio of 2 : 1. This result is direct evidence for the existence not only of the well-known 1:2 complex but also of a previously unreported 2: 1 complex. A further investigation of the variation of absorbance with pH suggests that this 2:1 complex contains four copper atoms. Although the precipitate has a 1: 1 stoichiometry, and although other workers have postulated the existence of a complex of this composition in solution, no evidence for this complex in solution was found in these investigations. The resolution of this contradiction is a compelling motive for further investigations on this system.
