Quantum dots offer a brighter future for photocatalysis

Photocatalysis has added a new dimension to organic synthesis in recent years, enabling chemists to develop more-efficient routes to complex molecules. Looking to take that success to another level, a research team at the University of Rochester has used small amounts of inexpensive quantum dots to seamlessly replace organic dyes and ruthenium and iridium complexes traditionally used as photocatalysts in C–C bond-forming reactions (J. Am. Chem. Soc. 2017, DOI: 10.1021/jacs.6b13379). Quantum dots are up-and-coming nanosized semiconducting materials best known for applications in biomedical imaging and color displays, but they have also been used to harvest light for metal catalysts in hydrogen production. Taking the catalysis application a step further, Rochester’s Jill A. Caputo, Todd D. Krauss, Daniel J. Weix, and coworkers found that 3-nm CdSe quantum dots with surface-capping carboxylate and phosphine ligands—they could be called “photodots”—can replace various types of photoredox catalysts in a set of standard reactions, including β-alkylation (shown), β-aminoalkylation, and reductive dehalogenation. The researchers note that quantum dots are inherently more light-stable, absorb more photons, have longer-lived excited states, and have broader absorption spectra than the other photocatalysts. The CdSe quantum dots aren’t a panacea for photocatalysis, Weix notes, as they aren’t effective for all the reaction types tested, but other sizes or types of quantum dots might prove even more useful.