New asymmetric N2S2 macrocycles,their metal chelates and the photokinetics of DNA-complex interaction

New asymmetric ligands have been synthesized by condensing o-phenylene diamine with CS₂ and PhCHO/MeCHO, and their complexes with Mn^II, Co^II, Ni^II, Cu^II and Zn^II were prepared and characterized by elemental analyses, conductivity measurements, i.r., u.v.–vis., e.p.r. and n.m.r. spectra. The transition metals in the complexes show square planar geometry and are ionic. Photokinetic studies of the DNA-metal complexes C₁₀H₁₀S₄N₂Cu](NO₃)₂ and C₁₀H₁₀S₄N₂Ni](NO₃)₂ were carried out and the rate constants k_{(DNA-complex)} were calculated. The results indicate that DNA reacts with the metal complex in two steps. DNA first undergoes structural degradation and is then completely hydrolysed as indicated by spectral changes consistent with earlier results. The asymmetric N₂S₂ macrocyclic metal complexes show a strong propensity for DNA inhibition and can be used as an intercalating binding model.