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Quantum chemical and quantum dynamical calculations areperformedfor a bay-substituted perylene bisimide dye up to its hexameric aggregate.The aggregate structure is determined by employing the self-consistentcharge density functional tight-binding (SCC-DFTB) approach includingdispersion corrections. It is characterized by a stabilization viatwo chains of hydrogen bonds facilitated by amide functionalities.Focusing on the central embedded dimer, the Coulomb coupling for thisJ-aggregate is determined by means of the time-dependent density functionaltheory (TDDFT) to be −514 cm–1. Exciton vibrationalcoupling is treated within the shifted oscillator model from whichfive strongly coupled modes per monomer are selected for inclusioninto a minimal dynamic model. Performing wave packet propagationsfor a model employing up to 7 electronic states and 30 vibrationalmodes using the multiconfiguration time-dependent Hartree method,aggregate absorption spectra are obtained and compared to experiment. [ABSTRACT FROM AUTHOR]

We present a theoretical study on the temperature-dependent absorption and photoluminescence spectroscopy of rubrene multichromophores by combining the time-dependent long-range-corrected density functional theory with the exciton model. The spectra of rubrene multichromophores up to heptamers are calculated, and the effects of exciton−phonon coupling and temperature on the photophysical properties of both H- and J-aggregated oligomers are addressed. It is found that the spectral behavior of rubrene aggregates is very much dependent on aggregation details. As the temperature increases, higher excitonic states become populated, and low-energy dark states in H-aggregated oligomers become observable gradually while the peak intensities near the 0−0 transition decrease for J-aggregated oligomers. [ABSTRACT FROM AUTHOR]