Lanthanide phosphorescence, antenna

Figure 2.18 Schematic representation of photophysical processes in lanthanide(III) complexes (antenna effect). A = absorption, F = fluorescence, P = phosphorescence, L = lanthanide-centred luminescence, ISC = intersystem crossing, ET = energy transfer S = singlet, T = triplet. Full vertical lines radiative transitions dotted vertical lines nonradiative transitions...

For phosphorescence, lanthanide metal ions can be used in a similar manner. Lanthanide ions have very interesting photophysical properties, but often exhibit weak absorption bands, and aggregate to form clusters, which limit their applications. Thus, a dendrimer that can provide a protective shell to isolate a cation and at the same time enhance the emission by transfer from the periphery to the lanthanide ion at the core could be of great interest. Self-assembled lanthanide-cored dendrimers have been prepared to prove such an assumption synthesis was carried out by mixing three equivalents of polyaryl ether dendrons bearing carboxylic acid entity at the focal point with Ln(III) cations [Er(III), Tb(III), and Eu(III)] (Fig. 5.4) [34]. The authors demonstrated that the enhancement of the lanthanide cation emission associated with the dendritic core shell was observed, and an antenna effect from the periphery to the core was shown to promote this process. 

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