Visible Light-Mediated Quantum Dot Photocatalysis Enables Olefination Reactions at Room Temperature

Abstract

The ability of quantum dots (QDs) to photocatalyze organic reactions is gaining attention because of their distinct light harvesting properties over traditional precious metal- and small molecule-based catalysts. However, establishing the potency of QD photocatalysts in diverse and useful organic transformations, as well as deciphering the charge transfer mechanism, is essential to cement their place as an efficient photocatalyst in synthetic chemistry. Here, we report the use of QDs in efficiently catalyzing a series of olefination reactions under visible-light irradiation at room temperature (90% yield). Spectroscopic and electrochemical studies reveal intriguing insights on the charge transfer mechanism involved in QD-photocatalyzed olefination. Interestingly, the dual role of triphenylphosphineas a surface passivating agent and nucleophileturned out to be decisive in directing the charge transfer process from the QD to the reactant. Benzyl triphenylphosphonium bromide salt was accepting the electrons from the photoexcited QDs, thereby initiating the catalytic olefination reaction. QD-photocatalyzed olefination was demonstrated with formaldehyde as well, resulting in the formation of industrially relevant terminal alkene, namely styrene. Moreover, the environmentally friendly indium phosphide (InP) QD also photocatalyzed the olefination reaction under mild reaction conditions, which proves the practical suitability of our study. This work presents an attractive and efficient way to introduce double bonds in organic molecules using QDs and visible light at room temperature.

EPR spin trapping of nucleophilic and radical reactions at colloidal metal chalcogenide quantum dot surfaces

“…For example, a recent report of CdSe-photocatalyzed aldehyde olefination with benzyl bromide may undergo selenide-centered benzylation in addition to the proposed photoinduced reaction steps. 50 These would be particularly important in reactions illuminated under high flux (with localized heating) or for reactions with low quantum yields. Such reactions could result in lower selectivity or lower product conversion or may even, in some cases, be the operative pathway for the photocatalytic products.…”

Advancements in semiconductor quantum dots: expanding frontiers in optoelectronics, analytical sensing, biomedicine, and catalysis

“…Their research therefore offered a productive way to use room-temperature visible light and CQDs to efficiently introduce double bonds into organic compounds. 303 Using CdSeS/CdZnSeS(Al)/ZnS CQDs as catalysts, Yu-Yun Yin et al developed a photocatalyzed three-component reaction combining malononitrile, benzaldehyde, and N , N -dimethylaniline that resulted in the production of α-aminobutyronitrile molecules through C–C bond formation. The well-dispersed CQD catalysts exhibited remarkable catalytic activity and stability, with a maximum quantum yield of 98% and a turnover number (TON) above 1.1 × 10 3 .…”

Inorganic–Organic Dual-Ligand-Regulated Photocatalysis of CdS@ZnxCd1–xS@ZnS Quantum Dots for Lignin Valorization

“…Quantum dots (QDs) possess multiple outstanding characteristics, including high photostability, large extinction coefficient, tunable band gap, and controllable surface chemistry. − These properties make QDs excellent photocatalysts for photocatalytic lignin valorization. In addition to the traditional single binary structure, researchers have explored various types of QDs, such as doped, alloyed, and core/shell structures .…”