Synthesis and time-gated fluorometric application of a europium(III) complex with a borono-substituted terpyridine polyacid ligand

A new europium(III) complex with a borono-substituted terpyridine polyacid ligand, (4′-borono-2,2′:6′,2″-terpyridine-6,6″-diyl) bis(methylenenitrilo) tetrakis(acetate)-Eu3+ (BTTA-Eu3+), has been designed and synthesized as a luminescence probe for hydrogen peroxide (H2O2). The complex is highly luminescent in aqueous buffers to display a typical Eu3+ emission pattern with a sharp emission peak at 610 nm and a long luminescence lifetime of 1.34 ms. Upon reaction with H2O2, the deboronation derivative of BTTA-Eu3+, (4′-hydroxy-2,2′:6′,2″-terpyridine-6,6″-diyl) bis(methylenenitrilo) tetrakis(acetate)-Eu3+ (HTTA-Eu3+), can be generated. It was found that the luminescence of BTTA-Eu3+ was pH-insensitive, whereas that of HTTA-Eu3+ was pH-dependent and could be remarkably weakened in neutral and basic buffers, which allowed BTTA-Eu3+ to be a luminescence probe for the time-gated luminescence detection of H2O2 in neutral and basic buffers. The H2O2–BTTA-Eu3+ system was applied to monitor the kinetics of the palladium-catalyzed Suzuki cross-coupling reaction between BTTA-Eu3+ and bromobenzene, which suggested a useful strategy for the application of time-gated luminescence technique in catalysis reaction researches.