Direct observation of photoinduced electron transfer in pyrene-labeled dU nucleosides and evidence for protonated 2`-deoxyuridine anion, dU(H){sup .}, as a primary electron transfer product
- Georgia State Univ., Atlanta, GA (United States)
- Washington State Univ., Pullman, WA (United States)
This paper examines the electron transfer (ET) photophysics of two pyrene-labeled nucleosides, 5-(1-carboxypyrenyl)-2`-deoxyuridine (1) and 5-(1-pyrenyl)-2`-deoxyuridine (2) by a variety of spectroscopies in several different solvents. For 1 in methanol (MeOH), a maximal change-in-absorbance ({Delta}A) increase at 460 nm characteristic of pyrene{sup .+} occurs during the time of photoexcitation (>=30 ps). These results prove that the S{sub 1} state Of pyrene is quenched due to intramolecular ET. Similar results are also obtained for 1 in acetonitrile (MeCN) where the pyrene{sup .+} absorbance at 460 nm decays in ca. 100 ps. For 1 and 2, changing solvent from MeOH to MeCN increases both emission lifetimes and quantum yields. For 2 the emission yield increases 13-fold, while for 1 it increases 3-fold. Even though the dielectric constants of MeOH and MeCN are similar, 33.6 and 37.5, respectively, both the large emission yield increase and the accompanying striking change in the emission spectrum for 2 on switching from MeOH to MeCN are consistent with lessened ET quenching due to raising the free energy of the pyrene{sup .+}/dU{sup .+} charge transfer product relative to the {pi},{pi}{sup *} state of pyrene, where dU = 2`-deoxyuridine. 73 refs., 6 figs., 2 tabs.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 174261
- Journal Information:
- Journal of Physical Chemistry, Vol. 99, Issue 51; Other Information: PBD: 21 Dec 1995
- Country of Publication:
- United States
- Language:
- English
Similar Records
Photoinduced electron transfer and enhanced triplet yields in benzo[a]pyrene derivative-nucleic acid complexes and covalent adducts
Photoinduced electron-transfer reactions in a chlorophyllide-pheophorbide cyclophane. A model for photosynthetic reaction centers