INTER-MOLECULAR ENERGY-TRANSFER BETWEEN LANTHANIDE COMPLEXES .6. INFLUENCE OF METAL-TO-LIGAND RATIO ON THE TRANSFER FROM TERBIUM(III) TO EUROPIUM(III) COMPLEXES OF L-HISTIDINE

The nature of the complexes formed between Tb3+ and L-histidine was investigated by making use of the fact that electronic energy can be absorbed by Tb3+/HIS complexes and subsequently transferred in a non-radiative manner to Eu3+/HIS complexes. The transfer was found to depend on the possible association of donor and quencher, and this information was used to outline the conditions under which the histidine complexes were found to self-associate. Supplementary information was obtained from measurements of the pH dependence of Tb3+ luminescence and differential absorbance spectra of Ho3+/HIS complexes. At low pH, the energy transfer occurred primarily by collisional means (implying the presence of monomeric complexes), whereas the transfer was governed by the formation of associated complexes at high pH. © 1979.