A series of Ru(bpy)(3)(2+)-(CH(2))(n)-MV(2+) complexes (, n = 3, 4, 7) used for DNA photocleavage have been designed and synthesized. Under the irradiation of visible light, complexes can cleave supercoiled plasmid DNA (pBR322) both in air and under Ar atmosphere. Radical species such as O(2)(-) , OH and the light-induced charge-separated (CS) oxidation state Ru(bpy)(3)(3+)-(CH(2))(n)-MV(+) are responsible for the cleavage. The longer the carbon chain linkage, the higher the DNA photocleavage efficiency. It is noted that backwards intramolecular electron transfer (ET) that exist in complexes can lead to some decreasing effect on the cleavage result, while inclusion of complexes with cucurbit[8]uril (CB[8]) inhibits the backwards ET to some extent, thereby increasing photocleavage efficiency.