Control and quantification of interchromophoric coupling in single-molecule defined shape-persistent oligomers
Physical Chemistry of Molecules, Liquids and Interfaces, Biophysical Chemistry
Polymer Materials
Final Report Abstract
In this project we succeeded in gaining a fundamental view of the intricate interplay of molecular morphology and electronic aggregation in extended oligomeric conjugated structures. Such oligomers, which are responsible for light absorption and emission, can be seen as the elementary building blocks, i.e. chromophores, of conjugated polymers used for organic electronic devices, e.g. organic light-emitting diodes or organic photovoltaic devices. By systematically synthesizing molecules in which the distance between neighboring chromophores and the number as well as the lengths of such chromophores was changed, we managed to uncouple the two predominant aggregation effects, termed J-type and H-type aggregation. The H-type coupling was investigated by theory and singlemolecule experiments, whereas in a next publication the focus lay on the J-type aggregation effect. By decreasing the distance between neighboring chromophores further and further, we were surprised to observe that bending of the chromophores must be considered. First, we observed unexpected spectroscopic results, for example a strongly decreased emission anisotropy, which we did not expect for straight chromophores. With the help of the simulations performed by the group of Prof. Grimme, we understood that bending of the chromophores must be considered and we saw this result as an opportunity to investigate this effect in more detail. Finally, we wanted to draw a connection between the electronic aggregation effects in our molecular model systems and bulk film properties, such as exciton diffusion. For this reason, we departed from the molecular model systems and investigated corresponding conjugated polymers and nanoparticles thereof. By employing a new photon correlation technique, picosecond time-resolved antibunching (psTRAB), we were capable to draw a connection between J- and H-type coupling and exciton diffusion in mesoscopic conjugated polymer nanoparticles. This led to a further DFG proposal (Quantifying the number of chromophores and the kinetics of exciton diffusion in nanoparticles with picosecond time-resolved photon antibunching (psTRAB)), which was recently awarded and in which the model systems developed here also play a role.
Publications
- “H-Aggregation Effects between π-Conjugated Chromophores in Cofacial Dimers and Trimers: Comparison of Theory and Single-Molecule Experiment” J. Phys. Chem. B 2018, 122, 6431-6441
C. Allolio, T. Stangl, T. Eder, D. Schmitz, J. Vogelsang, S. Höger, D. Horinek, J. M. Lupton
(See online at https://doi.org/10.1021/acs.jpcb.8b01188) - “Anomalous Linear Dichroism in Bent Chromophores of π-Conjugated Polymers: Departure from the Franck-Condon Principle” Phys. Rev. Lett. 2019, 122, 057402
P. Wilhelm, J. Vogelsang, N. Schönfelder, S. Höger, J. M. Lupton
(See online at https://doi.org/10.1103/physrevlett.122.057402) - “Interplay Between J- and H-Type Coupling in Aggregates of π- Conjugated Polymers: A Single-Molecule Perspective” Angew. Chem. Int. Ed. 2019, 58, 18898–18902
T. Eder, J. Vogelsang, S. Bange, K. Remmerssen, D. Schmitz, S.-S. Jester, T. J. Keller, S. Höger, J. M. Lupton
(See online at https://doi.org/10.1002/anie.201912374) - “Picosecond time-resolved photon antibunching measures nanoscale exciton motion and the true number of chromophores” Nature Communications 2021, 12, 1, 1327
G. J. Hedley, T. Schröder, F. Steiner, T. Eder, F. J. Hofmann, S. Bange, D. Laux, S. Höger, P. Tinnefeld, J. M. Lupton, J. Vogelsang
(See online at https://doi.org/10.1038/s41467-021-21474-z)
