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The Photophysical Properties of Triisopropylsilyl-ethynylpentacene—A Molecule with an Unusually Large Singlet-Triplet Energy Gap—In Solution and Solid Phases

1
CQC, Department of Chemistry, University of Coimbra, 3004-535 Coimbra, Portugal
2
Central Laser Facility, Research Complex at Harwell, STFC Rutherford Appleton Laboratory, Didcot OX11 0FA, UK
3
Molecular Photonics Laboratory, SNES, Newcastle University, Newcastle upon Tyne NE1 7RU, UK
4
Department of Polymer Engineering, Faculty of Technology, Duzce University, 81620 Duzce, Turkey
*
Author to whom correspondence should be addressed.
Chemistry 2020, 2(2), 545-564; https://doi.org/10.3390/chemistry2020033
Received: 26 April 2020 / Revised: 14 May 2020 / Accepted: 18 May 2020 / Published: 3 June 2020
(This article belongs to the Special Issue A Special Issue in Honor of Professor Josef Michl)
The process of singlet-exciton fission (SEF) has attracted much attention of late. One of the most popular SEF compounds is TIPS-pentacene (TIPS-P, where TIPS = triisopropylsilylethynyl) but, despite its extensive use as both a reference and building block, its photophysical properties are not so well established. In particular, the triplet state excitation energy remains uncertain. Here, we report quantitative data and spectral characterization for excited-singlet and -triplet states in dilute solution. The triplet energy is determined to be 7940 ± 1200 cm−1 on the basis of sensitization studies using time-resolved photoacoustic calorimetry. The triplet quantum yield at the limit of low concentration and low laser intensity is only ca. 1%. Self-quenching occurs at high solute concentration where the fluorescence yield and lifetime decrease markedly relative to dilute solution but we were unable to detect excimer emission by steady-state spectroscopy. Short-lived fluorescence, free from excimer emission or phosphorescence, occurs for crystals of TIPS-P, most likely from amorphous domains. View Full-Text
Keywords: singlet exciton fission; triplet state; molecular photophysics; polyacene; photoacoustic calorimetry; excimer singlet exciton fission; triplet state; molecular photophysics; polyacene; photoacoustic calorimetry; excimer
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Schaberle, F.A.; Serpa, C.; Arnaut, L.G.; Ward, A.D.; Karlsson, J.K.G.; Atahan, A.; Harriman, A. The Photophysical Properties of Triisopropylsilyl-ethynylpentacene—A Molecule with an Unusually Large Singlet-Triplet Energy Gap—In Solution and Solid Phases. Chemistry 2020, 2, 545-564.

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