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Green Photoredox Catalysis Using Near-Infrared Light: Two-Photon-Absorption Enabled Cyclization

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Authors
Author Name
Bidyut Kumar Kundu
Author Organization
University of Cincinnati
Author Name
Chuang Han
Author Organization
University of Cincinnati
Author Name
Christopher G. Elles
Author Organization
University of Kansas
Author Name
Yujie Sun
Author Organization
University of Cincinnati

Over the past two decades, there has been a significant surge of interest in the field of ultraviolet and/or visible (UV/vis) light photocatalysis. UV-vis irradiation merged with noble metal-based photosensitizers of Ru, Ir as catalysts is most useful combination in this segment as these metal photocatalysts mostly absorb in the UV/vis region. However, high energy UV/vis irradiation sources as well as the noble-metal based photosensitizer are not considered as green. Using organic fluorophores having excellent photophysical properties in the near infrared (NIR) region can be a crucial alternative for sustainable catalysis. Though, the absorption maximum of majority of the reported organic photosensitizers lies in the range of 300-500 nm. And, this region only covers a limited part of solar spectrum, thus, may limit the practical application of photocatalytic processes in certain conditions. By adopting two-photon absorption (TPA) strategy can offer the direct access to NIR region, but designing appropriate TPA photocatalyst needs judicially modulating donor-π-acceptor-π-donor-conjugated (D-π-A-π-D) structure. Inspired by previous report, designer pyridine-based organic photocatalysts with tunable branched octopolar D-A acritarches are synthesized, which show considerable TPA feature (up to 600 GM) with viscosity-dependent photophysical properties. In particular, the optimal organocatalyst showing the advantages of large TPA cross-section and long triplet state lifetime, can achieve the utilization of NIR light and control the direction of energy transfer for green photoredox cyclization.

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University of Cincinnati
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