Dependence of the lifetime upon the excitation energy and intramolecular energy transfer rates: the 5D0Eu(III) emission case.

In many Eu(III)-based materials, the presence of an intermediate energy level, such as ligand-to-metal charge transfer (LMCT) states or defects, that mediates the energy transfer mechanisms can strongly affect the lifetime of the (5)D(0) state, mainly at near-resonance (large transfer rates). We present results for the dependence of the (5)D(0) lifetime on the excitation wavelength for a wide class of Eu(III)-based compounds: ionic salts, polyoxometalates (POMs), core/shell inorganic nanoparticles (NPs) and nanotubes, coordination polymers, ß-diketonate complexes, organic-inorganic hybrids, macro-mesocellular foams, functionalized mesoporous silica, and layered double hydroxides (LDHs). This yet unexplained behavior is successfully modelled by a coupled set of rate equations with seven states, in which the wavelength dependence is simulated by varying the intramolecular energy transfer rates. In addition, the simulations of the rate equations for four- and three-level systems show a strong dependence of the emission lifetime upon the excitation wavelength if near-resonant non-radiative energy transfer processes are present, indicating that the proposed scheme can be generalized to other trivalent lanthanide ions, as observed for Tb(III)/Ce(III). Finally, the proper use of lifetime definition in the presence of energy transfer is emphasized.

Hydrolysis of 8-quinolyl phosphate monoester: kinetic and theoretical studies of the effect of lanthanide ions.

8-Quinolyl phosphate (8QP) in the presence of the trivalent lanthanide ions (Ln = La, Sm, Eu, Tb, and Er) forms a [Ln x 8QP]+ complex where the lanthanide ion catalyzes hydrolysis of 8QP. In reactions with Tb3+ or Er3+, there is evidence of limited intervention by a second lanthanide ion. Rate constants are increased by more than 10(7)-fold, and kinetic data and B3LYP/ECP calculations indicate that the effects are largely driven by leaving group and metaphosphate ion stabilization. The lanthanides favor a single-step D(N)A(N) mechanism with a dissociative transition state, with limited nucleophilic assistance, consistent with the low hydroxide ion dependence and the small kinetic effect of Ln3+ radii.