APTA: A Simple Ligand for Lanthanide Energy Transfer Luminescence in Aqueous Solution

Abstract

Amino-phenol triacetic acid (apta) has been evaluated as a potential sensitizing ligand for energy transfer  luminescence to lanthanide ions in aqueous media at pH 7.2. Photophysical data including quantum yields (Φ) excitation wavelength (265 nm), emission wavelength (544 nm) and excited state lifetimes (τ_water = 0.83 ms) for the 1:1 complex are reported. The number of water molecules coordinated to the metal ion has been calculated using isotopic experiments and these data were compared with the octadentate ligand bis-amino-phenol tetraacetic acid (bapta). Apta demonstrates excellent discrimination between Tb³⁺ and Eu³⁺ ions and apta is the simplest ligand reported thus far capable of functioning as an electronic energy transfer sensitizing moiety.

KEYWORDS:  Apta, terbium, sensitizer, luminescence.