A comparative DNA scission activity study of azaferrocene, N-methyl-azaferrocene iodide and 3,3′,4,4′-tetramethyl-1,1′-diphosphaferrocene (featuring iron in a +2 oxidation state), along with ferrocene (iron +2) and ferrocenium (iron +3) cation is described. Experiments indicate a high cleavage activity of azaferrocene and its N-methyl derivative in DMSO. DNA cleavage activity can be slowed down by addition of a free radical scavenger (thiourea) or triggered by addition of a reductive agent (dithiothreitol, DTT). The X-ray crystal structure of the N-methyl-2,5-dimethylazaferrocene cation (iron +2) with hexafluorophosphate as counter anion is also reported.