| Abstract
| - In this work nine DNA hairpins (HPs) are studied at room temperature to observe their pyrene•+/dU•- CTexcited-state dynamics following photoexcitation at 355 nm with a 25 ps laser pulse. The HPs are 18−24bases long, have a central tetra-T loop, and have a single UPE (5-(2-pyren-1-yl-ethylenyl)-2‘-deoxyuridine)substitution in the central region of their stems. Three of the HPs are also substituted with 5-XdU traps,where X = Br or F, to learn about the effects of these traps on CT excited-state lifetimes and emissionquantum yields in UPE substituted HPs. The combination of lengthened average CT lifetime and enhancedCT emission quantum yield in HPs with excess electron traps compared to HPs lacking traps strongly suggeststhat excess electrons are injected into the DNA stem at pyrimidine sites external to UPE as well via chargeseparation within UPE itself. Furthermore, the increased CT emission quantum yield in HPs with traps comparedto HPs without traps implies that externally injected electrons can migrate to uracil in UPE (i.e., Py•+dU) andthus indirectly form the emissive Py•+dU•- CT state of UPE.
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