Energy Transfer between <i>p</i>-Benzoylbenzoate and Europium Ethylenediaminetetraacetate in Water Solution

Abstract

Ultraviolet radiation absorbed by the p-benzoylbenzoate (p-BB−) ion in solution is transferred to an appreciable extent to the europium ethylenediaminetetraacetate (EuEDTA−) ion and is re-emitted as the visible red fluorescence characteristic of Eu3+. Fluorescence intensity is greater in D2O than in water. The fluorescence is quenched by dissolved O2. Although evidence for mixed ligand complexes involving p-BB− and EuEDTA− was obtained, fluorescence seems to result from ultraviolet absorption by free p-BB− ions followed by intermolecular energy transfer to free EuEDTA− ions. The analogous water systems containing o-BB− or m-BB− are nonfluorescent, although all three of the solid hydrated salts Eu(o-BB)3, Eu(m-BB)3, and Eu(p-BB)3 fluoresce brightly at room temperature.