Observing the Entry Events of a Titanium-Based Photoredox Catalytic Cycle in Real Time |
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Authors: | Jonas Schmidt Dr Luis I Domenianni Marcel Leuschner Prof Dr Andreas Gansäuer Prof Dr Peter Vöhringer |
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Institution: | 1. Clausius Institute for Physical and Theoretical Chemistry, Rheinische Friedrich-Wilhelms-Universität Bonn, Wegelerstraße 12, 53115 Bonn, Germany;2. Kekulé Institute for Organic Chemistry and Biochemistry, Rheinische Friedrich-Wilhelms-Universität Bonn, Gerhard-Domagk-Straße 1, 53121 Bonn, Germany |
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Abstract: | Titanium-based catalysis in single electron transfer (SET) steps has evolved into a versatile approach for the synthesis of fine chemicals and first attempts have recently been made to enhance its sustainability by merging it with photo-redox (PR) catalysis. Here, we explore the photochemical principles of all-Ti-based SET-PR-catalysis, i.e. in the absence of a precious metal PR-co-catalyst. By combining time-resolved emission with ultraviolet-pump/mid-infrared-probe (UV/MIR) spectroscopy on femtosecond-to-microsecond time scales we quantify the dynamics of the critical events of entry into the catalytic cycle; namely, the singlet-triplet interconversion of the do-it-all titanocene(IV) PR-catalyst and its one-electron reduction by a sacrificial amine electron donor. The results highlight the importance of the PR-catalyst's singlet-triplet gap as a design guide for future improvements. |
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Keywords: | Photo-Redox Catalysis Thermally Activated Delayed Fluorescence Time-Resolved Fluorescence Transition-Metal Photochemistry Ultrafast Infrared Spectroscopy |
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