Abstract
This Article describes the design of a colloidal quantum dot (QD) photosensitizer for the Pd-photocatalyzed Heck coupling of styrene and iodocyclohexane to form 2-cyclohexylstyrene. In the presence of 0.05 mol % CdS QDs, which have an emission spectrum that overlaps the absorption spectrum of a key Pd(II)alkyl iodide intermediate, the reaction proceeds with 82% yield for the Heck product at 0.5 mol % loading of Pd catalyst; no product forms at this loading without a sensitizer. A radical trapping experiment and steady-state and transient optical spectroscopies indicate that the QDs transfer energy to a Pd(II)alkyl iodide intermediate, pushing the reaction toward a Pd(I) alkyl radical species that leads to the Heck coupled product, and suppressing undesired β-hydride elimination directly from the Pd(II)alkyl iodide. Functionalization of the surfaces of the QDs with isonicotinic acid increases the rate constant of this reaction by a factor of 2.4 by colocalizing the QD and the Pd-complex. The modularity and tunability of the QD core and surface make it a convenient and effective chromophore for this alternative mode of cooperative photocatalysis.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 495-501 |
| Number of pages | 7 |
| Journal | Journal of the American Chemical Society |
| Volume | 142 |
| Issue number | 1 |
| DOIs | |
| State | Published - Jan 8 2020 |
Funding
We thank Dr. Mohamad S. Kodaimati for assistance with transient absorption. This research was primarily supported as part of the Center for Light Energy Activated Redox Processes (LEAP), an Energy Frontier Research Center funded by the U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES), under award no. DE-SC0001059 (synthesis, catalysis, data analysis, experimental design), and by the International Institute for Nanotechnology at Northwestern University through a fellowship to C.R.R. (experimental design and data analysis). This work made use of the IMSERC at Northwestern University, which has received support from the NIH (1S10OD012016-01/1S10RR019071-01A1); Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF ECCS-1542205); the State of Illinois; and the International Institute for Nanotechnology (IIN). We thank Dr. Mohamad S. Kodaimati for assistance with transient absorption. This research was primarily supported as part of the Center for Light Energy Activated Redox Processes (LEAP), an Energy Frontier Research Center funded by the U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES), under award no. DE-SC0001059 (synthesis, catalysis, data analysis, experimental design), and by the International Institute for Nanotechnology at Northwestern University through a fellowship to C.R.R. (experimental design and data analysis). This work made use of the IMSERC at Northwestern University, which has received support from the NIH (1S10OD012016-01/1S10RR019071-01A1); Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF ECCS-1542205); the State of Illinois; and the International Institute for Nanotechnology (IIN).
ASJC Scopus subject areas
- General Chemistry
- Biochemistry
- Catalysis
- Colloid and Surface Chemistry