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)) (ExBoxp>4+p>) to form both the ExBoxp>3+•p> and the doubly reduced ExBoxp>2(+•)p> 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 ExBoxp>2(+•)p> state has a lifetime of ∼10 ns, while CdSp>+•p>:ExBoxp>3+•p> recombines with multiple time constants, the longest of which is ∼300 μs. The long-lived charge separation and ability to accumulate multiple charges on ExBoxp>4+p> demonstrate the potential of the CdS:ExBoxp>4+p> complex to serve as a platform for two-electron photocatalysis.