DNA cleavage by the photolysis of cyclopentadienyl metal complexes: Mechanistic studies and sequence selectivity of strand scission by CpW(CO) ₃CH₃

The photolysis of CpW(CO)₃Me has been shown to produce methyl radicals and to cleave DNA in a single-stranded manner, and preliminary evidence implicated a carbon-centered radical in this process. In this work, the mechanism of strand scission in this reaction was determined to occur by hydrogen atom abstraction from the 4′- and 5′-positions of the deoxyribose moiety of the backbone of DNA. Additionally, in a side reaction that does not lead to frank strand scission, all four bases of DNA are methylated under these conditions; however, none of these base or backbone modifications lead to the formation of abasic sites.