Ultrafast Two-Electron Transfer in a CdS Quantum Dot–Extended-Viologen Cyclophane Complex

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• 作者：Ryan M. Young ; Stephen C. Jensen ; Kedy Edme ; Yilei Wu ; Matthew D. Krzyaniak ; Nicolaas A. Vermeulen ; Edward J. Dale ; J. Fraser Stoddart ; Emily A. Weiss ; Michael R. Wasielewski ; Dick T. Co
• 刊名：Journal of the American Chemical Society
• 出版年：2016
• 出版时间：May 18, 2016
• 年：2016
• 卷：138
• 期：19
• 页码：6163-6170
• 全文大小：580K
• 年卷期：0
• ISSN：1520-5126

文摘

Time-resolved optical spectroscopies reveal multielectron transfer from the biexcitonic state of a CdS quantum dot to an adsorbed tetracationic compound cyclobis(4,4′-(1,4-phenylene) bipyridin-1-ium-1,4-phenylene-bis(methylene)) (ExBox⁴⁺) to form both the ExBox^3+• and the doubly reduced ExBox^2(+•) states from a single laser pulse. Electron transfer in the single-exciton regime occurs in 1 ps. At higher excitation powers the second electron transfer takes ∼5 ps, which leads to a mixture of redox states of the acceptor ligand. The doubly reduced ExBox^2(+•) state has a lifetime of ∼10 ns, while CdS^+•:ExBox^3+• recombines with multiple time constants, the longest of which is ∼300 μs. The long-lived charge separation and ability to accumulate multiple charges on ExBox⁴⁺ demonstrate the potential of the CdS:ExBox⁴⁺ complex to serve as a platform for two-electron photocatalysis.