Energy Resonance Crossing Controls the Photoluminescence of Europium Antenna Probes

The energy transfer pathways in lanthanide antenna probes cannot be comprehensively rationalized by the currently available models, and their elucidation remains to be a challenging task. On the basis of quantum-chemical ab initio calculations of representative europium antenna complexes, an innovative energy resonance model is proposed, which is controlled by an overall nonet-quintet intersystem crossing on the basis of spin-orbit coupling among the sublevels of the involved states.