Encapsulation of Isolated Luminophores within Supramolecular Cages

The sequestration of luminophores within supramolecular polyhedral compartments of a crystalline zeolitelike hydrogen-bonded framework illustrates a unique approach to limiting the self-quenching ordinarily exhibited at the high concentrations achievable in this framework. A range of differently sized luminescent guests, namely coumarin 1, coumarin 4, fluorescein, [Ru(bpy)(3)]Cl-2, and rhodamine B, can be encapsulated in amounts of up to one molecule per cage, equivalent to a concentration of 0.175m, which is significantly higher than the concentration at which aggregation- induced quenching occurs in other media. The luminescence spectra of the encapsulated guests are consistent with the presence of isolated monomers and the absence of selfquenching. The emission color of the single crystals can be tuned readily from blue to red through the choice of guest molecules. These observations promise an approach to organic solid-state lasing compounds if crystals of sufficient size and quality can be prepared.