Polarographic Studies on interaction of 2-Aminoquinoxaline with Cd(II) in Alkanols, Formamide, Dimethyl Formamide and Dimethyl Sulphoxide Solvent Mixture

Abstract

The present study deals with the determination of composition
and stability constants of Cd(II)-2-aminoquinoxaline complexes in
25, 50 and 75% (by volume) aqueous methanol solution. In each
case, the single well defined reduction wave appeared. The plots of
i_d vs., confirmed that the reduction was of diffusion control.
The reversible nature of the electrode reaction was evident from
the slopes of the E_d.e vs. log i/i_d–i curves which were of the order
of 31 ± 2 m V. The indication of the formation of Cd(II) complexes
with 2-aminoquinoxaline was provided by the shift in the E_1/2 values
to more negative potentials ana decrease in the diffusion currents
with the increasing concentration of the ligand. The complexes
formed by 2-aminoquinoxaline are very weak which confirm the
validity of Deford and Hume's method to calculate the consecutive
formation constants of very weak complexes, which may not be
detected by other techniques. The low stabilities of the complexes
of 2-aminoquinoxaline may be due to the less tendency of the
amino-group to donate electrons because of delocalisation of
electrons in the heterocyclic ring. Thus it is obvious that the nature
and concentration of the solvent not only affects the stability, but
the composition of complexes formed also.