Intermolecular energy transfer and fluorescence in solid benzoyltrifluoroacetylacetonate lanthanide complexes

Abstract

Measurements of the relative fluorescence output of mixed crystals of type, (Eu, Gd)(btfa)₄(pipH)(btfa = benzoyltrifluoroacetylacetonate, pipH = piperidinium cation), indicate the occurrence of efficient intermolecular energy transfer. Experimental data suggest that energy migration occurs via ligand exciton bands with the Eu³⁺ ion acting as a trap. Possible involvement of singlet and/or triplet excitons is discussed and it is concluded that triplet excitons are directly involved. Investigations of crystals of type, (Eu,Nd,Gd)(btfa)₄(pipH), have given results consistent with this interpretation. In these crystals the Nd³⁺ acts as a second exciton trap and, in addition, evidence of direct transfer of energy from excited Eu³⁺ to Nd³⁺ ions has been obtained.