Document Type
Article
Publication Date
12-5-2024
Abstract
Thiophene polycyclic derivatives are widely used in organic light-emitting diodes, photovoltaics, and medicinal chemistry applications. Understanding the electronic and structural factors controlling their intersystem crossing rates is paramount for these applications to be successful. This study investigates the photophysical, electronic structure, and excited state dynamics of 1,2-benzodiphenylene sulfide, benzo[b]naphtho[1,2-d]thiophene, and benzo[b]naphtho[2,3-d]thiophene in polar aprotic and non-polar solvents. Steady-state absorption and emission spectroscopy, femtosecond transient absorption spectroscopy, and DFT and TD-DFT calculations are employed. Low fluorescence quantum yields of 1.2 to 2.7 % are measured in acetonitrile and cyclohexene, evidencing that the primary relaxation pathways in these thiophene derivatives are nonradiative. Linear interpolation of internal coordinates calculations predict that an S−C bond elongation reaction coordinate facilitates the efficient intersystem crossing to the T1 state. Excitation of 1,2-benzodiphenylene sulfide and benzo[b]naphtho[1,2-d]thiophene at 350 nm or benzo[b]naphtho[2,3-d]thiophene at 365 nm, populates the lowest-energy 1ππ* state, which relaxes to the 1ππ* minimum in tens of picoseconds or intersystem crosses to the triplet manifold in ca. 500 ps to 1.1 ns depending on the position at which the benzene rings are added. Excitation at 266 nm does not affect the intersystem crossing rates. Laser photodegradation experiments demonstrate that the thiophene polycyclic derivatives are highly photostable.
Keywords
environmental pollutants, intersystem crossing, polycyclic aromatic sulfur heterocycles, thiophene derivatives, π-conjugated systems
Language
English
Publication Title
Chemistry A European Journal
Rights
© 2024 The Author(s). Chemistry - A European Journal published by Wiley-VCH GmbH. This is an open access work distributed under the terms of the Creative Commons Attribution-Non-Commercial (https://creativecommons.org/licenses/by-nc/4.0/) which permits non-commercial reuse, distribution, and reproduction in any medium, provided the original work is properly cited.
Creative Commons License
This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License
Recommended Citation
C. Griffrith, S. E. Krul, S. J. Hoehn, T. Phan, C. E. Crespo-Hernández, Chem. Eur. J. 2024, 30, e202402721. https://doi.org/10.1002/chem.202402721
Manuscript Version
Final Publisher Version