1 research outputs found
Aggregation of an <i>n</i>–π* Molecule Induces Fluorescence Turn-on
Although <i>n</i>–π* molecules can serve
as electroluminescent materials because of the harvesting of singlet
and triplet excitons through El-Sayed-rule-allowed reverse intersystem
crossing, the weak fluorescence emissions of such molecules have prevented
applications into devices. We have discovered a 1 order of magnitude
enhancement of the fluorescence of a prototypical <i>n</i>–π* fluorophore, 7-phenylcoumarin (PC), upon aggregation.
We performed a mechanistic study consisting of structural, photophysical,
and quantum chemical investigations, and found that the aggregation
positioned the fluorescent electronic state below the nonemissive
triplet <i>n</i>–π* transition state. Our studies,
for the first time, demonstrate intramolecular geometry and intermolecular
arrangements in the solid state to be significant factors in the photoluminescence
quantum yields of <i>n</i>–π* fluorophores