Table 1.
Logarithm of overall stability constants logβ for In(III) complexes formed with deferiprone, maltol, HQ and HQS with the pKa values of the ligands.a (L is the completely deprotonated form of the ligands.) pM* (− log([M] + [M(OH)(1–4)]))b were computed at pH 7.4 at 1 μM In(III) or Ga(III) and 10 μM ligand concentrations. (Charges of the various species are omitted for clarity.) {T = 25.0 °C, I = 0.20 M (KCl)}
| Method | Deferiprone | Maltol | HQS | HQ | |
|---|---|---|---|---|---|
| pKa (H2L) | pH-pot | 3.66 ± 0.01c | ‒ | 3.89 ± 0.02 | 4.99d |
| pKa (HL) | pH-pot | 9.72 ± 0.01c | 8.47 ± 0.01 | 8.46 ± 0.02 | 9.51d |
| pKa (H2L) | UV–vis | 3.57 ± 0.02 | ‒ | 3.70 ± 0.04f | 4.90 ± 0.02g |
| pKa (HL) | UV–vis | 9.70 ± 0.02 | 8.39 ± 0.02e | 8.27 ± 0.04f | 9.63 ± 0.02g |
| logβ [InL] | pH-pot | 13.67 ± 0.04 h | 11.03 ± 0.03 | 12.64 ± 0.05 | ‒ |
| logβ [InL2] | pH-pot | 23.50 ± 0.06 h | 18.59 ± 0.03 | 21.31 ± 0.07 | ‒ |
| logβ [InL3] | pH-pot | 32.66 ± 0.08 h | 24.38 ± 0.05 | 28.95 ± 0.09 | ‒ |
| logβ [InL] | UV–vis | 13.72 ± 0.03 | 10.77 ± 0.03 | 12.29 ± 0.06 | 13.43 ± 0.06 |
| logβ [InL2] | UV–vis | 23.88 ± 0.06 | 18.78 ± 0.03 | 21.18 ± 0.06 | 22.87 ± 0.03 |
| logβ [InL3] | UV–vis | 33.45 ± 0.03 | 25.04 ± 0.06 | 29.66 ± 0.06 | 32.64 ± 0.06 |
| pIn* | 7.95 | 6.01 | 7.93 | 8.18 | |
| pGa* | 8.83i | 6.00j | 7.92j | 7.86j | |
aHydrolysis constants for In(III): logβ [InH‒1] = ‒4.30, logβ [InH‒2] = ‒9.40, logβ [InH‒3] = ‒13.90, logβ [InH‒4] = ‒23.40 [27]. Stability constants for In(III) chloride complexes: logβ [InCl] = 2.32, logβ [InCl2] = 3.62, logβ [InCl3] = 4.00 [28]. bChlorido complex formation is negligible at these conditions. cpKa (H2L) = 3.67, pKa (HL) = 9.77, I = 0.2 M (KCl) Ref. [31]. dTaken from Ref. [29]. epKa (HL) = 8.46, I = 0.2 M (KCl) Ref [29]. fpKa (H2L) = 3.63, pKa (HL) = 8.48, I = 0.2 M (KNO3) Ref. [30]. gpKa (H2L) = 4.95, pKa (HL) = 9.75, I = 0.2 M (KCl) Ref. [29]. hlogβ [InL] = 13.60, logβ [InL2] = 23.93, logβ [InL3] = 32.93 at I = 0.15 M NaCl [27]. iComputed based on stability constants taken from Ref. [27]. jComputed on the basis of stability constants taken from Ref. [29], hydrolysis constants for Ga(III): logβ [GaH‒1] = ‒2.46, logβ [GaH‒2] = ‒5.92, logβ [GaH‒3] = ‒10.63, logβ [GaH‒4] = ‒16.87 [32]