The study of the interactions of the ligands: [(η 5 -C 5 H 5 )Fe{(η 5 -C 5 H 4 )-CH=N-R]} {with R=CH 2 -CH 2 -N(CH 3 ) 2 , CH 2 -CH 2 -S-CH 2 -CH 3 or (L)- CH(COOCH 3 )-CH 2 -CH 2 -S-CH 3 (1a-1c)}, the coordination complexes: cis-[M(ligand)Cl 2 ] {with M=Pt(II) (2) or Pd(II) (3)} and the cyclopalladated compound: [Pd{(η 5 -C 5 H 5 )Fe[(η 5 -C 5 H 3 )-CH=N-CH 2 -CH 2 -N(CH 3 ) 2 )]}Cl] (4a) with Calf Thymus DNA is reported. Circular dichroism spectroscopy revealed that although the ligands do not significantly modify the ellipticity of the bands or their position, compounds cis-[M(ligand)Cl 2 ] (2-3) produced a decrease in the ellipticity of the positive band, indicating a B->C transformation with increasing winding of the DNA binding, while for (4a) the ellipticity of both positive and negative bands increased. In addition, the quantity of M I I incorporated to DNA increased according to the sequence: 4a<2<3. A comparative study of the changes in the electrophoretic mobility of pBR322 plasmid DNA showed that at high r i values complex 4a produced a retardation in the mobility of the circular covalently-closed form of DNA, which is similar to that induced by cisplatin at r i =0.1. Electrochemical studies based on cyclic voltammetry of 1-3 and 4a are also reported.