Relative efficiencies of CpM(CO)(n)CH(3) and CpM(CO)(n)Ph (M = Cr, Mo, W, and Fe) complexes in photoinduced DNA cleavage.

The relative efficiencies of photoinduced DNA cleavage by complexes of the type CpM(CO)(n)()R (M = Cr, Mo, or W, n = 3, R = CH(3) or Ph; M = Fe, n = 2, R = CH(3) or C(6)H(5)) have been investigated using a plasmid relaxation assay. Only the tungsten and iron complexes reproducibly caused single strand scission, in addition to which the iron systems efficiently gave double strand cleavage. The iron complexes gave strand scission at lower concentrations than the corresponding tungsten systems, with the phenyl complexes producing more damage than the methyl systems.