Macrocyclic complexes with lanthanoid salts part 38. Synthesis and luminescence study of homo- and hetero-binuclear complexes of lanthanides with a new cyclic compartmental Schiff base

Abstract

Homo- and hetero-binuclear lanthanide(III) complexes with the macrocyclic ligand H₂L¹ derived from the condensation of 4-chloro-2,6-diformylphenol and the polyamine NH₂(CH₂)₂O(CH₂)₂O(CH₂)₂NH₂ have been synthesized: [Ln₂L¹(NO₃)₄]·nH₂O (Ln = La, Pr, Sm, Eu, Gd, Tb, or Dy; n= 1 or 2) and [Ln_xLn′_{2 –x}L¹(NO₃)₄]·nH₂O (Ln,Ln′= La,Sm; La,Gd; La,Dy; La,Eu; Dy,Gd; Dy,Eu; Gd,Eu; Gd,Tb; Eu,Tb; or La,Tb; n= 1 or 2). Their possible structure and the interaction between the metal ions are discussed on the basis of spectroscopic, mass spectrometric, and magnetic data together with scanning electron microprobe analyses. Electron microscopy with X-ray fluorescence analysis as well as magnetic susceptibility measurements suggest that the complexes containing two different lanthanide ions may be truly heterobinuclear, with the two metal centres lying at a long distance from each other and not connected by any bridging heteroatoms. Laser-excited luminescence spectra and lifetimes also point to the presence of heterobinuclear species. The yield of the Tb^III to Eu^III energy transfer was quantified and the intermetallic distance evaluated.