Macrocyclic lanthanide(III) complexes of iminophenol Schiff bases and carboxylate anions: Syntheses, structures and luminescence properties

Abstract

The mixed-ligand lanthanide(III) complexes derived from the tetraiminodiphenolate (L1H2) or octaiminotetraphenolate (L2H4) macrocyclic ligands and acetate (OAc−) or benzoate (OBz−) anions have been synthesized and structurally characterized. With the ligand combination L1H2 and OBz−, either the dimeric complexes [{Ln(L1H2)}2(μ2-η1:η1-OBz)4](ClO4)2 (Ln=La (1), Nd (2) and Eu (3)) or the monomeric complexes [Ln(L1H2)(η2-OBz)2](ClO4)·n solvent (Ln=Tb (4), Lu (5) and Y (6)) have been obtained. The X-ray crystal structures of 1, 4 and 6 have been determined, of which 4 and 6 have the same structure. L1H2 and OAc− combination affords the dimeric complexes [{Ln(L1H2)(η2-OAc)(μ-OAc)}2](ClO4)2 (Ln=La (7), Nd (8) and Y (9)) and the structure of 9 has been determined. In complexes 1–9, L1H2 uses two imino nitrogens and the two phenolate oxygens for metal coordination, while the other two uncoordinated imine nitrogens are protonated and intramolecularly hydrogen-bonded to the phenolate oxygens. The metal centre in all the cases is 8-coordinate and has distorted square antiprism geometry. With the octaiminotetraphenolate macrocyclic ligand (L2H4) dinuclear complexes of composition [Ln2(L2H4)(OAc)2(NO3)4]·nH2O (Ln=La (10), Pr (11), Nd (12) and Y (13)) have obtained. The structures determined for 11 and 12 have shown that they are isostructural and there are two independent molecules (A and B) in the unit cell. The molecule A has the bond types [Ln2(L2H4)(η2-OAc)2(η2-NO3)2(η1-NO3)2] and its 9-coordinate metal centre obtains a tricapped trigonal prismatic geometry, while the molecule B is [Ln2(L2H4)(η2-OAc)2(η2-NO3)4] whose 10-coordinate metal centre has a sphenocorona geometry. In these compounds, four uncoordinated imine nitrogens are protonated and hydrogen-bonded to the phenolate oxygens. The luminescence spectra of [{Eu(L1H2)}2(μ-OBz)4]2+ (32+) in acetonitrile (at 298K) and in acetonitrile-toluene glassy matrix (at 77K) have been studied.