SYNTHESIS AND CHARACTERIZATION OF LANTHANIDE [LN(L)]2 COMPLEXES OF N4O3 AMINE PHENOL LIGANDS WITH PHENOLATE OXYGEN BRIDGES - EVIDENCE FOR VERY WEAK MAGNETIC EXCHANGE BETWEEN LANTHANIDE IONS

{The synthesis and characterization of three potentially heptadentate (N4O3) amine phenols and of a series of their mononuclear and dinuclear lanthanide complexes are reported. The heptadentate ligands are KBH4 reduction products of the Schiff bases derived from the condensation reactions of tris(2-aminoethyl)amine with 3 equiv of one of salicylaldebyde (tris(((2-hydroxybenzyl)amino)ethyl)amine (H3L1)), 5-chlorosalicylaldehyde (tris(((2-hydroxy-5-chlorobenzyl)amino)ethyl)amine (H3L2)), and 5-bromosalicylaldehyde (tris(((2-hydroxy-5-bromobenzyl)amino)ethyl)amine (H3L3)). The reaction of an amine phenol with 1 equiv of a lanthanide (Ln) nitrate produces the mononuclear complex [Ln(H3L)(NO3)3]; homodinuclear complexes [Ln(L)]2 were obtained from the reaction of lanthanide salts with the respective ligand in the presence of a base (hydroxide or acetate). The X-ray structure of [Gd(L1)]2.2CHCl3 (H3L1 = tris(((2-hydroxybenzyl)amino)ethyl)amine) has been determined; it is the first structurally characterized example of an [Ln(L)]2 complex, a homodinuclear eight-coordinate lanthanide complex [Ln(L)]2 with heptadentate ligands only. The complex crystallizes as a chloroform solvate in the triclinic space group P1BAR with a = 12.002 (2) angstrom