Tuning Excited-State Properties of [2.2]Paracyclophane-Based Antennas to Ensure Efficient Sensitization of Lanthanide Ions or Singlet Oxygen Generation.

The multistep synthesis of original antennas incorporating substituted [2.2]paracyclophane (pCp) moieties in the π-conjugated skeleton is described. These antennas, functionalized with an electron donor alkoxy fragment () or with a fused coumarin derivative (), are incorporated in a triazacyclonane macrocyclic ligand or , respectively, for the design of Eu(III), Yb(III), and Gd(III) complexes. A combined photophysical/theoretical study reveals that presents a charge transfer character via through-space paracyclophane conjugation, whereas presents only local excited states centered on the coumarin-paracyclophane moiety, strongly favoring triplet state population via intersystem crossing. The resulting complexes Eu and Yb are fully emissive in red and near-infrared, respectively, whereas the Gd complex acts as a photosensitizer for the generation of singlet oxygen.