A molecular basis to rare earth separations for recycling: tuning the TriNOx ligand properties for improved performance

A methoxy-substituted tripodal hydroxylamine ligand, H(3)TriNOx(OMe), was synthesized and coordinated to rare earth cations for separation purposes. Metrics of the resulting complexes were investigated and compared with their parent TriNOx(3-) counterparts for determination of the molecular basis for the described rare earth separation system. Addition of an electron donating group to the aryl backbone resulted in a more electron rich ligand that increased the equilbrium constant for complex dimerization five-fold. The new separation system yielded efficient Nd/Dy separations in toluene rather than benzene.