Figure 1.

The up-field region of the ¹H NMR spectra of [Tb(S-SSSS-1)(D₂O)]⁻ recorded at 295.2 K in D₂O 200 MHz (bottom) and of [Tb(S-RRRR-1)(D₂O)]⁻ recorded 332.7 K in D₂O at 200 MHz (top). The down-field regions of the spectra are not displayed owing to the limited bandwidth of the excitation pulse. The assignments of the protons of the macrocyclic ring are shown in which ax^S refers to the axial proton of the carbons located on the side of the ring and eq^S, the equatorial proton of the same carbon. eq^C refers to the equatorial proton located on the carbon located on the corner of the ring.[25] Molecular models of the complexes are also shown, illustrating the difference in coordination geometry between two stereoisomers.[26]