Influence of adduct stereochemistry and hydrogen-bonding solvents on photoinduced charge transfer in a covalent benzo[a]pyrene diol epoxide-nucleoside adduct on picosecond time scales

Journal Article · Thu Sep 29 00:00:00 EDT 1994 · Journal of Physical Chemistry; (United States)

DOI:https://doi.org/10.1021/j100090a017· OSTI ID:6835191

O'Connor, D ^[1]; Shafirovich, V Y; Geacintov, N E ^[2]

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1. Univ. of Texas, Austin, TX (United States)
2. New York Univ., NY (United States)

Photoinduced electron transfer occurs with different rate constants upon picosecond laser pulse excitation of the stereoisomeric (+)-trans- and (-)-cis-benzo[a]pyrene diol epoxide-N[sup 2]-deoxyguanosine covalently linked adducts (BPDE-N[sup 2]-dG, bond with 10S absolute configuration) in polar solvents (N,N[prime]-dimethylformamide (DMF), and the hydrogen-bonding liquids H[sub 2]O, D[sub 2]O, formamide (FA), and N-methylformamide (NMF)). In the case of (+)-trans-BPDE-dG in DMF, photoinduced electron transfer occurs in the normal Marcus region, from dG to the pyrenyl residue singlet with a rate constant k[sub s] = (9.1 [+-] 0.9) x 10[sup 9] s[sup [minus]1], which is followed by a slower recombination (k[sub r] = (1.8 + 0.5) x 10[sup 9] s[sup [minus]1]) in the inverted Marcus region. In the cis-stereoisomeric adduct, both rate constants are enhanced by a factor of approximately 5. The presence of the hydrogen-bonding network in NMF and FA exerts opposite effects on these rate constants, decreasing k[sub s] and increasing k[sub r] by factors of 2-5. In aqueous solutions these effects are even more pronounced, and radical ions are not observed since k[sub r] [much gt] k[sub s]. A kinetic isotope effect on the delay of the pyrenyl singlets in H[sub 2]O and D[sub 2]O (k[sub s](H[sub 2]O)/k[sub s](D[sub 2]O) = 1.3-1.5) suggests that a proton-coupled electron transfer mechanism may be operative in aqueous solutions. 51 refs., 10 figs., 2 tabs.

• OSTI ID: 6835191
• Journal Information: Journal of Physical Chemistry; (United States), Vol. 98:39; ISSN 0022-3654
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
59 BASIC BIOLOGICAL SCIENCES
ADDUCTS
MOLECULAR STRUCTURE
PHOTOCHEMICAL REACTIONS
AQUEOUS SOLUTIONS
BENZOPYRENE
CHEMICAL REACTION KINETICS
COMPILED DATA
ELECTRON TRANSFER
EPOXIDES
GLYCOLS
HYDROGEN
ISOTOPE EFFECTS
NUCLEOSIDES
SOLVENTS
STEREOCHEMISTRY
ALCOHOLS
AROMATICS
CHEMICAL REACTIONS
CONDENSED AROMATICS
DATA
DISPERSIONS
ELEMENTS
HYDROCARBONS
HYDROXY COMPOUNDS
INFORMATION
KINETICS
MIXTURES
NONMETALS
NUCLEOTIDES
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
REACTION KINETICS
RIBOSIDES
SOLUTIONS
400201* - Chemical & Physicochemical Properties
550400 - Genetics