Organic nanostructured host-guest materials containing three dyes

The authors have prepd. a new self-assembled fully org. host-guest system, where two and three emissive mols. are accommodated in the parallel nanochannels of a perhydrotriphenylene (PHTP) cryst. adduct. The guest mols. are p-terphenyl (1); 1,6-diphenyl-1,3,5-hexatriene (2); and pentathiophene (3). The emission from these materials is very efficient, since quenching effects typical of the solid-state phase are avoided. In the two-mol. system, the authors observe fast and efficient 1→2 energy transfer, with emission from a blue emitter reaching 100 % efficiency for an optimal diln. of the emissive mol. 2 with the higher-energy mol. 1. This material provides a perfect converter of light from UV to visible. By adding a lower-energy mol. 3 emitting in the green-orange region, the authors have realized a new host-guest material where a two-step resonance energy transfer 1→2→3 occurs. Anal. of the energy transfer mechanism occurring in the three-mol. system shows that the 2→3 energy transfer is slower than the 1→2 transfer, due to the larger mean distance between the 2 and 3 mols. However, thanks to the long lifetime of the blue-light-emitting 2 species, the slow 2→3 energy transfer populates the green-orange-light-emitting 3 species, extending the emission through nearly the whole visible region and maintaining good emission efficiencies of 60-70 %