Geometric dependencies of vibronically mediated excitation transfer in rylene dyads

TL;DR

This study investigates how the geometry of rylene dyads influences excitation transfer, revealing the importance of vibrational modes and thermal fluctuations in accurately modeling energy transport mechanisms.

Contribution

It introduces a vibronic dimer model that accounts for anharmonic vibrational modes and thermal fluctuations, improving understanding of excitation transfer in various geometries.

Findings

Vibrational dynamics significantly modulate excitation transfer.

Thermal fluctuations are crucial for accurate coupling estimates.

The vibronic model captures both F"{o}rster and strong coupling regimes.

Abstract

We study the excitation transfer in various geometric arrangements of rylene dimers using absorption, fluorescence and transient absorption spectra. Polarization and detection frequency dependencies of transient absorption track the interplay of transfer and vibrational relaxation within the dyads. We have resolved microscopic parametrization of intermolecular coupling between rylenes and reproduced transport data. Dynamical sampling of molecular geometries captures thermal fluctuations for Quantum Chemical estimate of couplings for orthogonally arranged dyad, where static estimates vanish and normal mode analysis of fluctuations underestimates them by an order of magnitude. Nonperturbative accounts for the modulation of transport by strongly coupled anharmonic vibrational modes is provided by a vibronic dimer model. Vibronic dynamics is demonstrated to cover both the F\"{o}rster transport regime of orthogonally arranged dyads and the strong coupling regime of parallel chromophores and allows us to model signal variations along the detection frequency.