Empirical method for prediction of the coordination environment of Eu(III) by time-resolved laser-induced fluorescence spectroscopy

摘要

The number of water molecules in the innersphere (N_(H2O)) was determined for Eu(III) and the strength of ligand field (R_(E/M)) was evaluated for a variety of coordination environments from the luminescence lifetime and the relative intensity at 615 nm and at 592 nm, by time-resolved laser-induced fluorescence spectroscopy. When R_(E/M) and ΔN_(H2O) for Eu(III) with a known coordination environment were plotted clear regularity was apparent between the location of the R_(E/M)-ΔN_(H2O) plot and the coordination environment of Eu(III). Here, ΔN_(H2O) was calculated by use of the equation, ΔN_(H2O) = 9 - N_(H2O). Unknown coordination environments of Eu(III) can, in turn, be characterized, including both the inner- and the outer-sphere, simply by plotting R_(E/M) and ΔN_(H2O) for Eu(III) on the diagram. This empirical method is effective for prediction of the coordination environment of hydrated and complexed Eu(III) in solutions and that of the adsorbed Eu(III) on ion-exchange resins and by microorganisms.