Highly sensitive energy-transfer luminescence of the N,N′-bis(2-hydroxybenzyl)-ethylenediamine-N,N′-diacetatoterbium(III) complex in aqueous solution

The luminescent properties of a terbium complex with a hexadentate ligand of N,N'-Bis(2-hydroxybenzyl)ethylenediamine-N,N'-diacetic acid (HBED) having a phenolate functional group as antenna moiety, have been investigated. The complex exhibits a high emission quantum yield (phi = 0.222, ex. 288 nm, em. 546 nm) with a long decay lifetime (tau H2O = 1.2 ms) in aqueous solution, which indicates energy-transfer type emission. The number of metal-bound water molecules in the complex was determined to be q = 1.8. The triplet energy level was estimated based on the data of its low-temperature phosphorescence. The calibration graph for Tb(III) was linear over the range from 3x10(-11) to 1x10(-8) mol dm(-3). A 3 sigma-blank detection limit of 3 ppt was achieved.