Table 3.
Rate constants characterizing the formation (kOH) and dissociation (M(L)OHkOH, M(L)(OH)2kOH) of [Fe(TRAP)]3−, [Ga(TRAP)]3−, [Ga(NOTA)], and [Ln(NOTA)] complexes (25°C).
| Formation kinetics | Dissociation kinetics | |||||
|---|---|---|---|---|---|---|
| kOH /M−1s−1 | M(L)OHkOH/s−1 | M(L)(OH)2kOH/s−1 | logKM(L)(OH)2 | kd/s−1 at pH = 7.4 | t1/2/h at pH = 7.4 | |
| [Fe(TRAP)]3− | (3.37 ± 0.02) × 104 | (4 ± 1) × 10−7 | (5.2 ± 0.4) × 10−4 | 13.4 (1) | 1.8 × 10−9 | 1.1 × 105 |
| [Ga(TRAP)]3− | (1.47 ± 0.02) × 105 | (4.3 ± 0.5) × 10−7 | (3.8 ± 0.2) × 10−6 | 10.9 (1) | 1.4 × 10−9 | 1.4 × 105 |
| [Ga(NOTA)]a | 1.14 × 105 | – | – | – | – | – |
| [Ce(NOTA)]b | 6.3 × 107 | – | – | – | – | – |
| [Gd(NOTA)]b | 7.1 × 107 | – | – | – | – | – |
| [Er(NOTA)]b | 5.5 × 107 | – | – | – | – | – |