Photoexcited Energy Transfer in a Weakly Coupled Dimer

Abstract

Nonadiabatic excited-state molecular dynamics (NA-ESMD) simulations have been performed in order to study the time-dependent exciton localization during energy transfer between two chromophore units of the weakly coupled anthracene dimer dithia-anthracenophane (DTA). Simulations are done at both low temperature (10 K) and room temperature (300 K). The initial photoexcitation creates an exciton which is primarily localized on a single monomer unit. Subsequently, the exciton experiences an ultrafast energy transfer becoming localized on either one monomer unit or the other, whereas delocalization between both monomers never occurs. In half of the trajectories, the electronic transition density becomes completely localized on the same monomer as the initial excitation, while in the other half, it becomes completely localized on the opposite monomer. In this article, we present an analysis of the energy transfer dynamics and the effect of thermally induced geometry distortions on the exciton localization. Finally, simulated fluorescence anisotropy decay curves for both DTA and the monomer unit dimethyl anthracene (DMA) are compared. Our analysis reveals that changes in the transition density localization caused by energy transfer between two monomers in DTA is not the only source of depolarization and exciton relaxation within a single DTA monomer unit can also cause reorientation of the transition dipole.

Carbon nanorings with inserted acenes: breaking symmetry in excited state dynamics

“…The agreement between the AM1 and the TDDFT results is quantitative for transition energies of multiple essential states defining electronic dynamics in this molecular family. The NA-ESMD has been extensively used to simulate internal conversion processes involving manifold of coupled electronic excited-states in a broad variety of extended conjugated molecules 80 81 82 83 , including [n]CPPs 84 .…”

Vibronic Quantum Beating between Electronic Excited States in a Heterodimer

“…EHR-NEXMD and SH-NEXMD), has been proved to be accurate enough to achieve a qualitative description of the photoinduced intramolecular energy in a large variety of multichromophoric molecular systems. 33,62,63,79,80 More details about the NEXMD approach, implementation, advantages and testing parameters can be found elsewhere. 47,70,81 NEXMD simulations allow us to analyse spatial exciton localization by calculating transition density matrices (TDM) 82,83…”

Excitation Energy Transfer in meta‐Substituted Phenylacetylene Multibranched Chromophores

“…These properties result from partial conjugation and flexible rotational motion of the entire branched structure through the central nitrogen core ,. On the other hand, those branched molecules with benzene, carbon, adamantine, and truxene as the central cores show a relatively slow energy transfer on the picosecond scale because of the nonconjugation of central core species ,,–,…”