Table 3.
1H and 15N NMR chemical shifts for the [15N]1,1/c,c-en species
| 1,1/c,c species[a] | en-15NH2(cis)[b] | en-15NH2(trans)[b] | 15NH2(linker)[b] | |||
|---|---|---|---|---|---|---|
| δ(1H) | δ(15N) | δ(1H) | δ(15N) | δ(1H) | δ(15N) | |
| 1 (Cl/Cl) | 5.01 | -30.8 | 5.47 | -30.9 | 4.48 | -43.5 |
| 2a (Cl/H(OH)) | [c] | [c] | [c] | [c] | [c] | [c] |
| 2b (Cl/H2O)[d] | 5.28 | -29.4 | 5.62 | -47.7 | 4.73 | -40.7 |
| (Cl/OH)[d] | 4.92 | -31.6 | 4.97 | -42.8 | 4.40 | -40.7 |
| μ-OH[e] | 5.32 | -27.3 | 5.34 | -46.2 | 4.62 | -39.4 |
| 3a (G/Cl) | [f] | [f] | 5.38 | -31.1 | 4.42 | -43.4 |
| 3c, 4 (G/Y) (Y=Cl or G) | 5.30-5.54 | -27.9 | 5.40-5.86 | -31.4 | [g] | [g] |
| 5.24-5.76 | -26.6 | 5.55-5.98 | -29.4 | |||
[a]
The labels 1-4 refer to the complexes shown in Scheme 1 in which the ligand Y≠Y’ is a=Cl, b=H2O, c=G N7.
[b]
1H referenced to TSP; 15N referenced to 15NH4Cl (external).
[c]
The peaks are coincident with the peaks of the Cl/Cl species.
[d]
Based on fitting pH titration curves for H2O/H2O species (Figure 5).
[e]
Hydroxo-bridged macrochelate species observed only in solutions of the diaqua species.
[f]
Possible resonances shielded with respect to the Cl/Cl species would be too close to the 1H2O signal to observe.
[g]
Concealed by the 1H2O peak at δ≈4.8 ppm. The 15N shift is around -40.6 ppm.