Ruthenium(II) terpyridyl complexes exhibiting DNA photocleavage: the role of the substituent on monodentate ligand.
Five ruthenium(II) complexes, [Ru(II)(tpy)(dppz)(py-R)](2+) (tpy = 2,2':6',2''-terpyridine; dppz = dipyrido[3,2-a:2',3'-c]phenazine; py-R = 4-substituted pyridine; R = N(CH(3))(2), NH(2), OCH(3), H, NO(2)), were synthesized; and the substituent effects on the photophysical property, electrochemical property, DNA binding, and DNA photocleavage of the complexes were examined carefully. Increasing the electron-donating ability of the substituent R from NO(2) to N(CH(3))(2) leads to a cathodic shift of Ru-based oxidation potential, a red shift of the (1)MLCT absorption at room temperature and the (3)MLCT emission at 77 K, and enhancement of the DNA photocleavage ability. DNA photocleavage control experiments and the EPR spin-trapping technique confirm that the photocleavage abilities of the complexes originate from (1)O(2) production. Time-resolved absorption spectra suggest that the (3)MLCT lifetime plays an important role in the photosensitized (1)O(2) generation of these complexes, which in turn depends strongly on the electron-donating ability of the substituent R. By changing the substituent of pyridine from the electron-withdrawing to the electron-donating group, the photocleavage abilities of the complexes varied from inactive to active, providing a new strategy for the development of DNA photocleavers of tpy-based Ru(II) complexes.
Zhou
Qian-Xiong
QX
Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China.
Yang
Fan
F
Lei
Wan-Hua
WH
Chen
Jing-Rong
JR
Li
Chao
C
Hou
Yuan-Jun
YJ
Ai
Xi-Cheng
XC
Zhang
Jian-Ping
JP
Wang
Xue-Song
XS
Zhang
Bao-Wen
BW
D004247:DNA / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy; D008024:Ligands; D019906:Nuclear Magnetic Resonance, Biomolecular; D010777:Photochemistry; D017975:Ruthenium Compounds / Q000737:chemistry*; D013113:Spin Labels
D008024:Ligands; D017975:Ruthenium Compounds; D013113:Spin Labels; D004247:DNA