Exciton Delocalization Counteracts the Energy Gap: A New Pathway toward NIR-Emissive Dyes
Journal article, 2021

Exciton coupling between the transition dipole moments of ordered dyes in supramolecular assemblies, so-called J/H-aggregates, leads to shifted electronic transitions. This can lower the excited state energy, allowing for emission well into the near-infrared regime. However, as we show here, it is not only the excited state energy modifications that J-aggregates can provide. A bay-alkylated quaterrylene was synthesized, which was found to form J-aggregates in 1,1,2,2-tetrachloroethane. A combination of superradiance and a decreased nonradiative relaxation rate made the J-aggregate four times more emissive than the monomeric counterpart. A reduced nonradiative relaxation rate is a nonintuitive consequence following the 180 nm (3300 cm-1) red-shift of the J-aggregate in comparison to the monomeric absorption. However, the energy gap law, which is commonly invoked to rationalize increased nonradiative relaxation rates with increasing emission wavelength, also contains a reorganization energy term. The reorganization energy is highly suppressed in J-aggregates due to exciton delocalization, and the framework of the energy gap law could therefore reproduce our experimental observations. J-Aggregates can thus circumvent the common belief that lowering the excited state energies results in large nonradiative relaxation rates and are thus a pathway toward highly emissive organic dyes in the NIR regime.

Author

Alexei Cravcenco

University of Gothenburg

Yi Yu

University of Gothenburg

Fredrik Edhborg

Chalmers, Chemistry and Chemical Engineering, Chemistry and Biochemistry

Jonas F. Goebel

University of Gothenburg

Zoltan Takacs

University of Gothenburg

Yizhou Yang

University of Gothenburg

Bo Albinsson

Chalmers, Chemistry and Chemical Engineering, Chemistry and Biochemistry

Karl Börjesson

University of Gothenburg

Journal of the American Chemical Society

0002-7863 (ISSN) 1520-5126 (eISSN)

Vol. 143 19232-19239

Areas of Advance

Nanoscience and Nanotechnology (SO 2010-2017, EI 2018-)

Materials Science

Subject Categories

Physical Chemistry

Chemical Sciences

DOI

10.1021/jacs.1c10654

More information

Latest update

12/1/2021