Synthesis, Characterization and Crystal Structure of Complexes of Rare Earth Picrates with N,N,N',N',N",N"-Hexaisopropyl- 2,2',2"-[nitrilotris(ethyleneoxy)]triacetamide (L)

Abstract

A new tripodal compound, N,N,N',N',N",N"-hexaisopropyl-2,2',2"-[nitrilotris(ethyleneoxy)]triacetamide (L) was synthesized. Its complexes with rare earth picrates, [M(Pic)L](Pic)2·H2O (M = La, Pr, Nd, Sm, Eu, Tb, Er, Yb, Y), have been prepared and characterized by elemental analysis, thermal analysis, conductivity measurements, IR and 1H NMR spectra. The crystal structures of two complexes [M(Pic)L](Pic)2 (M = Sm, Y) have been determined, which reveal that the M(III) ions (M = Sm, Y) are encapsulated by the three chains of the ligand and nine-coordinated by the central nitrogen atom, three ether oxygen atoms and three carbonyl oxygen atoms from the ligand, and two oxygen atoms from the didentate coordinated picrate ion in both cases. The results show that L acts as a heptadentate ligand, forming a cup-like coordination structure to accommodate the rare earth ion. Both rare earth complexes have the similar coordinate modes in spite of different unit cells.