Polarographic investigation of Cu(II) complexes with N,N,N',N'-tetrakis-(2-hydroxypropyl)-ethylenediamine

During investigation of the formation of Cu(2+) ion complexes with N,N,N',N'-tetrakis-(2-hydroxypropyl)-ethylenediamine (Quadrol-Q) by means of constant current polarography (20 degrees C, ionic strength J = 3 mol l(-1)), the possibility of the formation of two complex compounds; CuQ(2+) and CuQ(2+)(2), was shown within the pH range from 6 to 8. The logarithms of the stability constants for these compounds are 10.6 +/- 0.5 and 14.6 +/- 0.4 respectively. Cu(II) complexation increases sharply when the pH increases from 8 to 10. It was shown that the data at a pH of greater than 10 are in accordance with the existence of the hydroxy complexes CuQ(OH)(2) and CuQ(2)(OH)(2), the logarithms of the stability constants being 26.9 +/- 0.5 and 29.1 +/- 0.3.