期刊
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
卷 142, 期 1, 页码 495-501出版社
AMER CHEMICAL SOC
DOI: 10.1021/jacs.9b11278
关键词
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资金
- Center for Light Energy Activated Redox Processes (LEAP), an Energy Frontier Research Center - U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES) [DE-SC0001059]
- International Institute for Nanotechnology at Northwestern University
- NIH [1S10OD012016-01/1S10RR019071-01A1]
- Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource [NSF ECCS-1542205]
- State of Illinois
- International Institute for Nanotechnology (IIN)
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 beta-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.
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