A leap forward in green photochemistry: singlet fission in water solution

Abstract

Abstract We provide the first direct evidence of singlet fission occurring with water-soluble compounds. Perylene-3,4,9,10-tetracarboxylic forms dynamic oligomers in aqueous solution, with lifetimes long enough to allow intermolecular processes such as singlet fission. As these are transient oligomers rather than large, stable aggregates, they retain a significant degree of disorder. We performed a comprehensive analysis of such dynamic assemblies using time-resolved absorption and fluorescence spectroscopy, nuclear magnetic resonance spectroscopy, and theoretical modelling, allowing us to observe the characteristic signatures of singlet fission and develop a model to explain the different species observed. Our findings reveal that the twist and tilt angles between perylenes are key in favoring either singlet fission or charge separation. The efficiency of triplet formation is higher than 100% and the disordered system leads to triplets living in the nanosecond time range.