Table 2.
Formation constants (logβ) of the Fe(III), Fe(II), Cu(II) and Zn(II) complexes with HQNO2-L-Pro determined by UV-vis spectrophotometric titrations. (H2L is the neutral form of the ligand, charges of the complexes are omitted for clarity.) {I = 0.1 M (KCl); t = 25.0 °C}.
| logβ | Fe(III) | Fe(II) | Cu(II) | Zn(II) |
|---|---|---|---|---|
| [M(HL)] | 19.75 ± 0.03 | 16.52 ± 0.03 | 19.40 ± 0.03 | 17.36 ± 0.03 |
| [M(L)] | − | 8.39 ± 0.03 | 14.45 ± 0.03 | n.d. a |
| [M(HL)2] | 38.76 ± 0.03 | 32.74 ± 0.03 | 38.60 ± 0.03 | 33.71 ± 0.06 |
| [M(HL)(L)] | − | − | 31.75 ± 0.03 | n.d. a |
| [M(L)2] | − | − | 22.99 ± 0.03 | n.d. a |
| [M(HL)3] | 55.66 ± 0.03 | 47.60 ± 0.06 | − | − |
a Data were evaluated at pH < 8.