COFLUORESCENCE OF EU3-ACIDS( IN COMPLEXES OF AROMATIC CARBOXYLIC)

The fluorescence of Eu3+ in certain Eu3+-aromatic acid complexes were enhanced by over two orders of magnitude, by the addition of La3+; a p rocess referred to as cofluorescence. Cofluorescence was observed only with certain aromatic acid ligands; trismesic acid, pyromellitic acid and mellitic acid; thereby clearly establishing a correlation between the structure of the ligand and the process of cofluorescence. While cofluorescence has been extensively studied using beta-diketones as li gands, our studies demonstrate cofluorescence for the first time in li gands other than beta-diketones. Furthermore, the mechanism of cofluor escence in the aromatic acid complexes studied by us appears to be dif ferent from that operating in the beta-diketones. While intermolecular energy transfer is believed to occur in the beta-diketones, formation of polynuclear complexes appears to be responsible for cofluorescence in the aromatic acid ligands. (C) 1997 Elsevier Science B.V.