Thermally Activated Photophysical Processes of Organolanthanide Complexes in Solution

The effect of temperature upon the lanthanide luminescence lifetime and intensity has been investigated in toluene solution for the complexes LnPhen(TTA)(3) (Ln = Eu, Sm, Nd, Yb; Phen = 1,10-phenanthroline; TTA = thenoyltrifluoroacetonate). Thermally excited back-transfer to a charge transfer state was found to occur for Ln = Eu and can be explained by lifetime and intensity back-transfer models. The emission intensity and lifetime were also quenched with increasing temperature for Ln = Sm, and the activation energy for nonradiative decay is similar to that for the thermal population of Sm3+ excited states. Unusual behavior for lifetime and intensity was found for both Ln = Nd, Yb. The usually assumed equivalence of tau/tau(0) = I/I-0 (where tau is lifetime and I is intensity) does not hold for these cases. We infer that for these lanthanide systems the intensity decreases with temperature in the stage prior to population of the luminescent state. The lifetime changes are discussed.

Automated summary

This study investigates the effect of temperature on the lanthanide luminescence lifetime and intensity in toluene solution for various complexes. An unusual behavior was observed for some lanthanide systems, challenging the typically assumed relationship between lifetime and intensity.