Laser Flash Photolysis on Electron Transfer Reactions between 1,8-Dihydroxyanthraquinone with Adenine and Cytosine

Electron transfer (ET) reactions between 1,8-dihydroxyanthraquinone (DHAQ) and two DNA bases, adenine (A) and cytosine (C), have been investigated in CH3CN/H2O solution with nanosecond time-resolved laser flash photolysis. After irradiation at 355 nm, the triplet DHAQ is produced via intersystem crossing and reacts with two nucleobases. ET processes for both reactions have been definitely identified, in which two bases play a significant role of electron donor. Based on the measured decay dynamics of various intermediates and the corresponding quenching rates, an initial ET process followed by a secondary proton-transfer reaction is suggested for both the overall reactions. By plotting the observed quenching rate against the concentration of two DNA bases, the bimolecular quenching rate constants are determined as 9.0x10(8) L/(mol.s) for the (3)DHAQ*+C reaction and 3.3 x 10(8) L/(mol.s) for the (3)DHAQ*+A reaction, respectively.