Spectral study of mixed chelates of rare earths—III: Mixed salicylaldehydato complexes of rare earths with different neutral ligands

Abstract

A number of mixed ligand complexes of rare earth ions La 3+, Pr 3+, Nd 3+, Sm 3+, Eu 3+, Tb 3+, with salicylaldehyde as the valence neutralising ligand and phenenthroline, bipyridine, quinoline and pyridine as neutral ligands have been synthesised and their composition established. The neutral ligands do not absorb in the excitation region of the complex but vary in size and geometry. Therefore the emission spectra of these complexes may reflect the effect of the distortion of the microsymmetry on the emission characteristics of the metal ions. The u.v., visible and i.r. spectra of the complexes have been studied. The electronic absorption band of salicylaldehydato group has been compared with that of the complexes with Cu 2+, Ni 2+ and Co 2+ and has been shown to be a intramolecular charge transfer (IMCT) band. The luminescence spectra of the Eu 3+ complexes show that in the solid state the symmetry forbidden electric dipole transition intensity is much enhanced for Eu-(sald) 3(phen) which contains only one phenanthroline as compared to Eu(salicylate) 3(phen) 2 which has more symmetrical geometry. The simple complexes are very poor emitter. In solution, the ratio of E.D./M.D. transition intensities have the same low values in comparison to solids, for all the salicylaldehydato complexes. For the salicylate complexes this ratio is the same for the solution and the solid states.