Lanthanide intersystem crossing

It has been shown in the case of /i-diketonate complexes of lanthanides that the excited singlet state of the ligand goes to the ligand triplet by intersystem crossing and then energy is transferred from the ligand triplet to the metal ion manifold. Finally, the emission occurs from the excited state of the metal. 

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...

Figure 8 Simplified Jablonski diagram showing the sensitization pathway from the chromophoric hgand L to the lanthanide ion Ln " via the triplet state T of the sensitizer. The k values are the rate constants for aU photophysical phenomena involved. Absorption by the sensitizer, intersystem crossing kisc of the sensitizer, and energy transfer k from the triplet state of the sensitizer to the lanthanide ion (to one of its excited spectroscopic level) resulting in an...

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