Ultra long-lived triplet excited state in water at room temperature: Insights on the molecular design of tridecafullerenes.

Suitably engineered molecular systems exhibiting triplet excited states with very long lifetimes are important for high-end applications in nonlinear optics, photocatalysis or biomedicine. We report the finding of an ultra long-lived triplet with a mean lifetime of 93 ms in aqueous phase at room temperature, measured for a globular tridecafullerene with a highly compact glycodendrimeric structure. A series of three tridecafullerenes bearing different glycodendrons and spacers to the C 60 units have been synthesized and characterized. UV/Vis spectra and DLS experiments prove their aggregation in water. Steady state and time-resolved fluorescence experiments suggest a different degree of inner solvation of the multifullerenes depending on their molecular design. Efficient quenching of the triplet states by O 2 but not by waterborne azide anion has been observed. Molecular modelling reveals dissimilar access of the aqueous phase to the internal structure of the tridecafullerenes, differently shielded by the glycodendrimeric shell.