Elucidating complex triplet-state dynamics in the model system isopropylthioxanthone

Nikolaos Liaros; Sandra A. Gutierrez Razo; Matthew D. Thum; Hannah M. Ogden; Andrea N. Zeppuhar; Steven Wolf; Tommaso Baldacchini; Matthew J. Kelley; John S. Petersen; Daniel E. Falvey; Amy S. Mullin; John T. Fourkas

iScience (Jan 2022)

Elucidating complex triplet-state dynamics in the model system isopropylthioxanthone

Nikolaos Liaros,
Sandra A. Gutierrez Razo,
Matthew D. Thum,
Hannah M. Ogden,
Andrea N. Zeppuhar,
Steven Wolf,
Tommaso Baldacchini,
Matthew J. Kelley,
John S. Petersen,
Daniel E. Falvey,
Amy S. Mullin,
John T. Fourkas

Affiliations

Nikolaos Liaros: Department of Chemistry & Biochemistry, University of Maryland, College Park, MD 20742, USA
Sandra A. Gutierrez Razo: Department of Chemistry & Biochemistry, University of Maryland, College Park, MD 20742, USA
Matthew D. Thum: Department of Chemistry & Biochemistry, University of Maryland, College Park, MD 20742, USA
Hannah M. Ogden: Department of Chemistry & Biochemistry, University of Maryland, College Park, MD 20742, USA
Andrea N. Zeppuhar: Department of Chemistry & Biochemistry, University of Maryland, College Park, MD 20742, USA
Steven Wolf: Department of Chemistry & Biochemistry, University of Maryland, College Park, MD 20742, USA
Tommaso Baldacchini: Newport Corporation, 1791 Deere Avenue, Irvine, CA 92606, USA
Matthew J. Kelley: Newport Corporation, 1791 Deere Avenue, Irvine, CA 92606, USA
John S. Petersen: Department of Chemistry & Biochemistry, University of Maryland, College Park, MD 20742, USA; imec, Kapeldreef 75, 3001 Leuven, Belgium
Daniel E. Falvey: Department of Chemistry & Biochemistry, University of Maryland, College Park, MD 20742, USA
Amy S. Mullin: Department of Chemistry & Biochemistry, University of Maryland, College Park, MD 20742, USA
John T. Fourkas: Department of Chemistry & Biochemistry, University of Maryland, College Park, MD 20742, USA; Institute for Physical Science & Technology, University of Maryland, College Park, MD 20742, USA; Maryland Quantum Materials Center, University of Maryland, College Park, MD 20742, USA; Maryland NanoCenter, University of Maryland, College Park, MD 20742, USA; Corresponding author

Journal volume & issue: Vol. 25, no. 1
p. 103600

Abstract

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Summary: We introduce techniques for probing the dynamics of triplet states. We employ these tools, along with conventional techniques, to develop a detailed understanding of a complex chemical system: a negative-tone, radical photoresist for multiphoton absorption polymerization in which isopropylthioxanthone (ITX) is the photoinitiator. This work reveals that the same color of light used for the 2-photon excitation of ITX, leading to population of the triplet manifold through intersystem crossing, also depletes this triplet population via linear absorption followed by reverse intersystem crossing (RISC). Using spectroscopic tools and kinetic modeling, we identify the reactive triplet state and a non-reactive reservoir triplet state. We present compelling evidence that the deactivation channel involves RISC from an excited triplet state to a highly vibrationally excited level of the electronic ground state. The work described here offers the enticing possibility of understanding, and ultimately controlling, the photochemistry and photophysics of a broad range of triplet processes.

Published in iScience

ISSN: 2589-0042 (Online)
Publisher: Elsevier
Country of publisher: United States
LCC subjects: Science
Website: http://www.cell.com/iscience/home

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