Prolonging the Triplet Excited‐State Lifetime via Tandem Through‐Space Conjugation in Tetracationic Cyclophanes for Efficient Metal‐Free Photoredox Catalysis
Abstract
ABSTRACT Prolonging the triplet excited‐state lifetime is essential for developing efficient photocatalytic systems. Herein, a series of viologen‐based cyclophane derivatives ( 2 , 6 , and 8 ) featuring TSC were designed and synthesized, with TSC‐boxes 6 and 8 incorporating a unique combination of cyclophane structures and TSC units. Compared with 2 and 6 , which possess only a single TSC unit, TSC‐box 8 with a tandem TSC structure exhibits enhanced spin‐orbit coupling and a narrower singlet‐triplet energy gap. These attributes endow TSC‐box 8 with favorable photoelectric properties, including photoluminescence and an apparent one‐step four‐electron redox behavior. Nanosecond transient absorption spectroscopy revealed efficient formation of the triplet excited state, prolonging the triplet excited‐state lifetime, thereby enabling effective generation of O 2 •− and •OH. As a photocatalyst, TSC‐box 8 efficiently mediates metal‐free photoredox catalysis, affording benzimidazole derivatives in up to 99% yield and enabling the selective oxidation of toluene to benzaldehyde within 1 h (yield: 90%, conversion: 96%) and to benzoic acid within 5 h (yield: 97%, conversion: 98%). This work provides a strategic approach to designing long‐lived triplet excited‐state systems for metal‐free photocatalysis.
Article Details
Authors (12)
Yawen Li
Qi Sun
Zengrong Wang
Frontier Institute of Science and Technology, Interdisciplinary Research Center of Frontier science and technology, State Key Laboratory for Strength and Vibration of Mechanical Structures, Engineering Research Center of Key Materials For Efficient Utilization of Clean Energy of Shaanxi Province, Xi'an Key Laboratory of Electronic Devices and Material Chemistry Xi'an Jiaotong University Xi'an Shaanxi P. R. China
Cui Yi
Frontier Institute of Science and Technology, Interdisciplinary Research Center of Frontier Science and Technology, State Key Laboratory for Strength and Vibration of Mechanical Structures, Institute of New Concept Sensors and Molecular Materials, Shaanxi Key Laboratory of New Conceptual Sensors and Molecular Materials, Engineering Research Center of Key Materials for Efficient Utilization of Clean Energy of Shaanxi Province, Xi’an Key Laboratory of Electronic Devices and Material Chemistry
Tianle Cao
Frontier Institute of Science and Technology, Interdisciplinary Research Center of Frontier Science and Technology, State Key Laboratory for Strength and Vibration of Mechanical Structures, Institute of New Concept Sensors and Molecular Materials, Shaanxi Key Laboratory of New Conceptual Sensors and Molecular Materials, Engineering Research Center of Key Materials for Efficient Utilization of Clean Energy of Shaanxi Province, Xi’an Key Laboratory of Electronic Devices and Material Chemistry
Zhijie Zhou
Department of Chemistry and the Hong Kong Branch of Chinese National Engineering Research Centre for Tissue Restoration & Reconstruction, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong SAR 999077, China
Naiyao Li
Frontier Institute of Science and Technology, Interdisciplinary Research Center of Frontier Science and Technology, State Key Laboratory for Strength and Vibration of Mechanical Structures, Institute of New Concept Sensors and Molecular Materials, Shaanxi Key Laboratory of New Conceptual Sensors and Molecular Materials, Engineering Research Center of Key Materials for Efficient Utilization of Clean Energy of Shaanxi Province, Xi’an Key Laboratory of Electronic Devices and Material Chemistry
Wenxin Wei
Frontier Institute of Science and Technology, Interdisciplinary Research Center of Frontier Science and Technology, State Key Laboratory for Strength and Vibration of Mechanical Structures, Institute of New Concept Sensors and Molecular Materials, Shaanxi Key Laboratory of New Conceptual Sensors and Molecular Materials, Engineering Research Center of Key Materials for Efficient Utilization of Clean Energy of Shaanxi Province, Xi’an Key Laboratory of Electronic Devices and Material Chemistry
Wei Zhang
Haonan Peng
Key Laboratory of Inorganic Functional Materials and Devices, Shanghai Institute of Ceramics
Yu Fang
Gang He