Relative efficiencies of CpM(CO)nCH3 and CpM(CO)nPh (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 = CH3 or Ph; M = Fe, n. = 2, R = CH3 or C6H5) 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.