Terthiophene Photophysics Revisited: Independence of the Triplet Quantum Yield on the Excitation Wavelength

Article Article scientifique Article Terthiophene Photophysics Revisited: Independence of the Triplet Quantum Yield on the Excitation Wavelength eng 2025-07-29 author Wega Johannes 0000-0002-3142-6210 Department of Physical Chemistry, University of Geneva, CH-1211 Geneva, Switzerland. 403450 Chimie physique (groupe 6) (CHIF6) author Guignard Franck Olivier 0009-0004-8623-8032 Department of Physical Chemistry, University of Geneva, CH-1211 Geneva, Switzerland. 967080 author Vauthey Eric 0000-0002-9580-9683 Department of Physical Chemistry, University of Geneva, CH-1211 Geneva, Switzerland. 133895 Département de chimie physique (CHIFI) 7984-7989 10.1021/acs.jpclett.5c02050 40730826 1948-7185 https://pubs.acs.org/doi/10.1021/acs.jpclett.5c02050 A significant part of our understanding of the excited-state properties of polythiophenes comes from studies of smaller oligothiophenes, which have a better-defined structure. Among them, terthiophene (3T ) was reported to have an excitation-wavelength dependent triplet quantum yield, ΦT . This was explained by the opening of a second intersystem crossing (ISC) pathway upon the high-energy excitation of distorted molecules. Here, we reinvestigate the excited-state dynamics of 3T in solvents of various viscosity and in a polymer film. Our results reveal that, although different subpopulations are excited upon high- and low-energy irradiation, the ISC dynamics, and hence ΦT , are the same. We show that the distorted molecules excited at short wavelength undergo rapid planarization independent of the viscosity of the environment before significant ISC takes place. The apparent increase of ΦT with increasing excitation wavelength reported earlier can be explained by the neglect of the early relaxation dynamics. Dewey 540 38 Département de chimie physique 142 false 686 Groupe Vauthey The journal of physical chemistry letters 16 6b467040-f4ee-49b0-b2c3-4cba55db7549 Article (Accepted version) Public Terthiophene.pdf 1078871 application/pdf Restricted 2026-07-30 6f1bcfa4efc6600068f4dc6a28046d24e02ffc9448e473b706f291c5eb84371e 55b2364b-cf2d-4eb5-923f-34e13ad26130 Article (Published version) Restricted WegaJPCL25B.pdf 2174534 application/pdf 48f161ca2a424c4df6ba50cea768bc89a62dee5381a9629a6a751f4731845ee1 embargoedAccess Faculté des sciences / Section de chimie et biochimie / Département de chimie physique

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Terthiophene Photophysics Revisited: Independence of the Triplet Quantum Yield on the Excitation Wavelength	The journal of physical chemistry letters			2025	49	0

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Guignard, Franck Olivier