Addressing the Frenkel and charge transfer character of exciton states with a model Hamiltonian based on dimer calculations: Application to large aggregates of perylene bisimide

To understand the influence of interchromophoric arrangements on photo-induced processes and optical properties of aggregates, it is fundamental to assess the contribution of local excitations [charge transfer (CT) and Frenkel (FE)] to exciton states. Here, we apply a general procedure to analyze th...

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Bibliographic Details
Published in:The Journal of chemical physics 2021-03, Vol.154 (12), p.124101
Main Authors: Canola, Sofia, Bagnara, Giuseppe, Dai, Yasi, Ricci, Gaetano, Calzolari, Alessandro, Negri, Fabrizia
Format: Article
Language:English
Subjects:
Aggregates
Charge transfer
Chromophores
Density functional theory
Dimers
Excitation
Excitons
Mathematical models
Optical properties
Physics
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Summary:To understand the influence of interchromophoric arrangements on photo-induced processes and optical properties of aggregates, it is fundamental to assess the contribution of local excitations [charge transfer (CT) and Frenkel (FE)] to exciton states. Here, we apply a general procedure to analyze the adiabatic exciton states derived from time-dependent density functional theory calculations, in terms of diabatic states chosen to coincide with local excitations within a restricted orbital space. In parallel, motivated by the need of cost-effective approaches to afford the study of larger aggregates, we propose to build a model Hamiltonian based on calculations carried out on dimers composing the aggregate. Both approaches are applied to study excitation energy profiles and CT character modulation induced by interchromophore rearrangements in perylene bisimide aggregates up to a tetramer. The dimer-based approach closely reproduces the results of full-aggregate calculations, and an analysis in terms of symmetry-adapted diabatic states discloses the effects of CT/FE interactions on the interchange of the H-/J-character for small longitudinal shifts of the chromophores.
ISSN:0021-9606
1089-7690
DOI:10.1063/5.0045913