Photoinduced Energy and Electron Transfer Between a Photoactive Cage Based on a Thermally Activate Delayed Fluorescence Ligand and Encapsulated Fluorescent Dyes

The vast majority of polyhedral assemblies prepared by combining organic bent ligands and “photophysically innocent” palladium(II) metal ions are nonemissive. We report here a simple strategy to switch on the luminescence properties of a polyhedral assembly by combining a thermally activated delayed fluorescence (TADF) organic emitter based on a dipyridylcarbazole ligand scaffold with Pd2+ ions, giving rise to a luminescent Pd6L12 molecular cube. The assembly is capable of encapsulating within its cavity up to three molecules per cage of fluorescein, in its neutral lactone form, and up to two molecules of Rose Bengal in its dianionic quinoidal form. Photoinduced electron transfer (PeT) between the photoactive cage and the encapsulated Fluorescein and photoinduced energy transfer (PET) from the cage to encapsulated Rose Bengal have been observed by steady-state and time-resolved emission spectroscopy.