The Pivotal Role of Hot Carriers in Plasmonic Catalysis of C−N Bond Forming Reaction of Amines

• Published in: Angewandte Chemie International Edition Vol. 60; no. 22; pp. 12532 - 12538
• Main Authors: Swaminathan, Swathi, Rao, Vishal Govind, Bera, Jitendra K., Chandra, Manabendra
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 25-05-2021
• Edition: International ed. in English
• Subjects: Amines; Catalysis; Catalytic oxidation; charge carrier injection; Current carriers; Energy charge; gold; Intermediates; Magnetic resonance spectroscopy; Nanoparticles; NMR; NMR spectroscopy; Nuclear magnetic resonance; Oxidation; Potential energy; Raman spectroscopy; Reaction intermediates; Reaction mechanisms; redox chemistry; Redox potential; Spectroscopy; Spectrum analysis; surface plasmon resonance; gold; nanoparticles; surface plasmon resonance; charge carrier injection; redox chemistry
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.202101639

Here, we demonstrate the simultaneous utilization of both the hot carriers (electrons and holes) in the photocatalytic transformation of benzylamine to N‐benzylidenebenzylamine and the scope of reaction has also been successfully demonstrated with catalytic oxidation of 4‐methoxybenzylamine. The wavelength‐dependent excitation of AuNP allows us to tune the potential energy of charge carriers relative to the redox potential of the reactants which leads to energetically favorable product formation on the nanoparticle surface. We capture the formation of reaction intermediates and products by using in situ Raman spectroscopy, complemented by NMR spectroscopy and GC‐MS. Based on the experimental substantiations, a plausible reaction mechanism has been proposed.
A simple gold nanoparticle catalyzes the oxidative coupling of benzylamine to form imine in presence of visible light. Photoexcitation of Au NP generates an electron–hole pair that activates adsorbates (reactants) at Au NP surface to form a strong oxidant–reductant pair (benzylamine radical cation and superoxide radical), which is conducive for the reaction at a low temperature, with high product yield and selectivity.