来源：ACS Publications
A catecholate proligand, 2,3–dihydroxy–4,6–di–tert–butyl–benzaldehyde ([trenHC═N(H2tBu2cat)3]), capable of binding two metal cations, and its complexes RE2[trenHC═N(tBu2cat)3], RE = La, Nd, and Dy were synthesized. X-ray structures of the complexes showed that C–O bond lengths, ranging from 1.317(4) to 1.334(3) Å, and C–C bond lengths, ranging from 1.426(3) to 1.443(3) Å, of the complexes were consistent with the catecholate form of the ligand in all cases. Cyclic voltammetry (CV) measurements revealed the oxidation of the catecholate ligand arms to the semiquinonate form in all three metal complexes. The oxidation potentials for the metal complexes are modulated to shift toward more positive potentials with increasing Lewis acidity. The results support the hypothesis that differences in ligand oxidation potentials can be exploited for realizing systems for the separation of rare earth metals.