Modified dipicolinic acid ligands for sensitization of europium(III) luminescence

George, Michael R., Golden, Christopher A., Grossel, Martin C. and Curry, Richard J. (2006) Modified dipicolinic acid ligands for sensitization of europium(III) luminescence. Inorganic Chemistry, 45 (4), 1739-1744. (doi:10.1021/ic051461u).

Abstract

The effect of substitution of the 4- and 3,5-position in the pyridine ring of europium(III) pyridine-2,6-dicarboxylate complexes has been investigated with particular emphasis on sensitization of the Eu3+ ion. Sensitization of the Eu3+ 615nm emission was achieved through excitation of the ligands in which the 4-substituent was –H, -OH, and –Cl and the 3,5-position was -H. In these cases the ligand-to-Eu3+ ratio was confirmed as being 3:1. The sensitization was found to increase following substitution of the 4-position in the order Cl > H > OH. This is attributed to energy transfer occurring from the ligands into different Eu3+ intra-atomic energy levels, with spin selection rules governing the efficiency of this process. The Eu3+ luminescence lifetime was measured and found to vary from 1.16 to 2.90ms depending on excitation energy, ligand, and solvent. For the case of the 3,5-dibromo-4-hydroxy derivative no sensitization was observed and a ligand- to-Eu3+ ratio 1:1 was found. The solubility of these complexes in water and their long emission lifetime make them attractive for use as probes in biological systems.

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Contributors

Author: Martin C. Grossel

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