Semiconductor quantum dots (QDs) offer many potential advantages over small molecules for photoredox catalysis because of their high photostability, dynamic surface chemistry, and different photophysical properties. Recent advances have found a synergy between photoredox catalysts and transition metal catalysts (especially nickel catalysts), offering new opportunities for reaction development. While a growing number of reports on the use of QDs in various photoredox reactions have appeared, no reports have explored the use of QDs with nickel catalysts for C-C bond formation. We have examined several readily available QDs in a prototypical reaction: the nickel-catalyzed photoredox assisted cross-electrophile coupling of aryl bromides with alkyl bromides. Our data show that 5.9 nm CdS QDs are robust and effective photocatalysts for this reaction, providing high QD turnover numbers (&lt;39,500 TON) with comparable substrate scope to the published iridium-dye catalysts. NMR studies demonstrate that triethanolamine (TEOA) is capable of remodeling the QD surface in-situ by displacing strongly binding ligands including phosphonate and carboxylate ligands, forming TEOA-capped QDs that are suspected to be the active catalyst. In contrast, amine reductants that do not coordinate to the QD surface were less effective, demonstrating the potential of using QD surface chemistry as a handle for reaction development.

Semiconductor quantum dots in photoredox-assisted nickel catalysis

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