Site-dependence of van der Waals interaction explains exciton spectra of double-walled tubular J-aggregates

TL;DR

This paper extends the Frenkel exciton model to include site-dependent van der Waals interactions, successfully explaining the exciton spectra of double-walled tubular dye aggregates and highlighting the importance of dispersive effects.

Contribution

The work introduces a method to incorporate site-dependent dispersive energy shifts into the Frenkel exciton model for large dye aggregates.

Findings

Site-dependent energy shifts explain spectral splitting.

Van der Waals interactions are crucial for accurate optical property modeling.

The extended model aligns well with experimental spectra.

Abstract

The simulation of the optical properties of supramolecular aggregates requires the development of methods, which are able to treat a large number of coupled chromophores interacting with the environment. Since it is currently not possible to treat large systems by quantum chemistry, the Frenkel exciton model is a valuable alternative. In this work we show how the Frenkel exciton model can be extended in order to explain the excitonic spectra of a specific double-walled tubular dye aggregate explicitly taking into account dispersive energy shifts of ground and excited states due to van der Waals interaction with all surrounding molecules. The experimentally observed splitting is well explained by the site-dependent energy shift of molecules placed at the inner or outer side of the double-walled tube, respectively. Therefore we can conclude, that inclusion of the site-dependent dispersive effect in the theoretical description of optical properties of nanoscaled dye aggregates is mandatory.