Title: Role of dark states and Stokes shift simulations for tetraphenylpyrazine compared to other donor-acceptor photosensitizers
Authors: Javier Hernández-Rodríguez, Alberto Martín Santa Daria, Marina Soledad Alquegui, Lola González-Sánchez, Sandra Gómez
DOI: https://doi.org/10.1002/cphc.202400563
Date: 01/08/2024
Working Group: WG2
Grant Period: 2024
Grant Period Goal (number): GAPG-6/WG5, GAPG-8, GAPG-2
Covered deliverables from the MoU (number): 1.1.1
Countries involved: Spain
Number of female/young/ITC coauthors: 3/4/0
Abstract: An excellent agreement for simulated and measured absorption and emission spectra is found for four donor-acceptor aromatic molecules (tetraphenylpyrazine, tetraphenylethene, distirylanthracene and hexaphenylsilole) whose derivatives serve as solid state photosensitizers. After comparing several hybrid TDDFT functionals, EOM-CCSD, and experiments, the best agreement was found with TD-B3LYP and double zeta basis sets (6-31G** and def2-SVP) for one molecule in gas phase. A full characterisation of twelve to twenty electronic excited states was performed in every system. Symmetry-forbidden bands are found in the absorption spectra by sampling a hundred vibrationally geometries from a Wigner distribution. The density of states in the region 2-6 eV was also analysed, showing a very packed region of excited states and suggesting that dark electronic states may play a role in the dynamics of some of the photoexcited systems. Further calculations were done with QM/xTB at geometries extracted from previously published X-ray data to evaluate the influence of the environment on the excitations of the four aggregated molecular crystals.
