Berlin 2024 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 12: Molecular Electronics and Excited State Properties I
CPP 12.5: Vortrag
Montag, 18. März 2024, 17:15–17:30, H 0106
Exploring the Mechanisms behind Non-Aromatic Fluorescence Using the DFTB Method — Gonzalo Díaz Mirón1, •Carlos R. Lien-Medrano2, Debarshi Banerjee1, Uriel N. Morzán1, Ralph Gebauer1, and Ali Hassanali1 — 1ICTP, Trieste, Italy — 2University of Bremen, Bremen, Germany
In contrast to our standard textbook spectroscopic intuition, which attributes the fluorescence in biological systems to aromatic or conjugated groups, there are intriguing cases where non-aromatic systems exhibit inherent absorption and fluorescence in the UV-visible range. Noteworthy examples include amyloid structures, individual non-aromatic amino acids and amino acids derivatives. This study aims to comprehensively evaluate the potential of the TD-DFTB method implemented in DFTB+ [1] to investigate the photophysics underlying non-aromatic fluorescence (NAF) phenomena. The focus is on amino-acid crystals, particularly L-glutamine and its chemically transformed counterpart, L-pyro-ammonium. By comparing TD-DFTB results to previous TD-DFT studies and experimental findings [2, 3], the research successfully demonstrates TD-DFTB's accuracy in capturing non-radiative decay pathways and fluorescence origins. Furthermore, TD-DFTB is utilized to explore environmental effects using a QM/MM approach, providing insights into the experimentally observed Stoke-Shift and revealing new nuances in non-radiative decay mechanisms.
[1] Hourahine, B., et al. JCP, 152(12), 124101. (2020)
[2] Stephens, A. D., et al. PNAS, 118(21).(2021)
[3] Mirón, G. D., et al. Nature Communications, 14(1), 7325. (2023)
Keywords: Non-Aromatic Fluorescence; TD-DFT; Surface Hopping; QM/MM