Synthesis and characterization of new heterodinuclear (4f, 4f') lanthanide complexes

A tripodal compartmental Schiff base ligand resulting from reaction of 3-ethoxysalicylaldehyde and tris(2-aminoethyl)amine can yield heterodinuclear lanthanide complexes in which the Ln ions are coordinated in the inner N4O3 and the outer O3O3 sites. The key compound in this synthetic route is the neutral mononuclear complex in which the lanthanide ion is chelated in the inner N4O3 coordination site. Introduction of the second lanthanide ion as a trifluoroacetate salt yields heterodinuclear entities which are soluble enough to be characterized by electrospray mass spectrometry techniques. With the help of the lanthanide induced shifts observed in the 1H NMR spectra of different heterodinuclear complexes, we have been able to confirm that the equivalent chloride species are not subject to scrambling in methanol solution