LUMINESCENCE SPECTROSCOPIC STUDY OF EUROPIUM(III) AND TERBIUM(III) WITH ETHYLENEDIAMINE IN DIMETHYL-SULFOXIDE

The luminescence excitation and emission spectra of europium(III) and terbium(III) complexes of ethylenediamine (en) in dimethyl sulfoxide have been studied. The 7F-7(0)-->5D0 spectra of Eu(III) and the values of the luminescence decay constant confirmed that trivalent lanthanides form 1:1, 1:2 and 1:3 inner-sphere complexes with en. The quenching of the luminescence of Eu(III) and Tb(III) are linearly proportional to the number of N-H groups attached to the metal ions. The equations are k(obs) (Eu) = 0.759 n(N-H) + 0.416 and k(obs)(Tb) = 0.073 n(N-H) + 0.299. The quenching mechanism is assumed to be the same as that of the O-H group, ie. it involves coupling between the electronic transition energy of Eu(III) or Tb(III) and the vibrational overtones of N-H. Luminescence spectra and decay contents measured between 15 and 80-degrees-C indicate decreased stability of the complexes with increased temperature, in agreement with the reported enthalpies of complexation.