Synthesis, crystal structure and interaction with DNA and HSA of (N,N'-dibenzylethane-1,2-diamine) transition metal complexes

A new ligand, N,N′-dibenzylethane-1,2-diamine (L) and its four transition metal(II) complexes, ML₂(OAc)₂ · 2H₂O (M = Cu, Ni, Zn, Co), have been synthesized and characterized by elemental analysis, mass spectra, molar conductivity, NMR and IR. Moreover, the crystals structure of Cu(II) and Ni(II) complexes characterized by single crystal X-ray diffraction showed that the complexes have a similar molecular structure. Ni(II) has an regular octahedral coordination environment complexes, but typical Jahn Teller effect influenced Cu(II) in an elongated octahedral environment. The interaction between complexes and calf thymus DNA were studied by UV and fluorescence spectra measure, which showed that the binding mode of complexes with DNA is intercalation. Under physiological pH condition, the effects of Cu(OAc)₂L₂ · 2H₂O and Ni(OAc)₂L₂ · 2H₂O on human serum albumin were examined by fluorescence. The results of spectroscopic measurements suggested that the hydrophobic interaction is the predominant intermolecular force. The enthalpy change ΔH⁰ and the entropy change ΔS⁰ of Cu(OAc)₂L₂ · 2H₂O and Ni(OAc)₂L₂ · 2H₂O were calculated to be −11.533 kJ mol⁻¹ and 46.339 J mol⁻¹ K⁻¹, −11.026 kJ mol⁻¹ and 46.396 J mol⁻¹ K⁻¹, respectively, according to the Scatchard’s equation. The quenching mechanism and the number of binding site (n ≈ 1) were also obtained from fluorescence titration data.